This is a very interesting article so I have included most of it here, apart from the citations. They specifically bring attention here to the subject of Canada’s plan to utilize surgical masks in the event of a pandemic and conclude it may not work.
Volume 12, Number 11–November 2006 Perspective
Review of Aerosol Transmission of Influenza A Virus
Raymond Tellier*†
Suggested citation for this article
Abstract In theory, influenza viruses can be transmitted through aerosols, large droplets, or direct contact with secretions (or fomites). These 3 modes are not mutually exclusive. Published findings that support the occurrence of aerosol transmission were reviewed to assess the importance of this mode of transmission. Compelling evidence in the literature indicates that aerosol transmission of influenza is an important mode of transmission, which has obvious implications for pandemic influenza planning, and in particular for recommendations about the use of N95 respirators as part of personal protective equipment.
Concerns about the likely occurrence of an influenza pandemic in the near future are increasing. The highly pathogenic strains of influenza A (H5N1) virus circulating in Asia, Europe, and Africa have become the most feared candidates for giving rise to a pandemic strain.
Several authors have stated that large-droplet transmission is the predominant mode by which influenza virus infection is acquired (1–3). As a consequence of this opinion, protection against infectious aerosols is often ignored for influenza, including in the context of influenza pandemic preparedness. For example, the Canadian Pandemic Influenza Plan and the US Department of Health and Human Services Pandemic Influenza Plan (4,5) recommend surgical masks, not N95 respirators, as part of personal protective equipment (PPE) for routine patient care. This position contradicts the knowledge on influenza virus transmission accumulated in the past several decades. Indeed, the relevant chapters of many reference books, written by recognized authorities, refer to aerosols as an important mode of transmission for influenza (6–9).
In preparation for a possible pandemic caused by a highly lethal virus such as influenza A (H5N1), making the assumption that the role of aerosols in transmission of this virus will be similar to their role in the transmission of known human influenza viruses would seem rational. Because infection with influenza A (H5N1) virus is associated with high death rates and because healthcare workers cannot as yet be protected by vaccination, recommending an enhanced level of protection, including the use of N95 respirators as part of PPE, is important. Following are a brief review of the relevant published findings that support the importance of aerosol transmission of influenza and a brief discussion on the implications of these findings on pandemic preparedness.
Influenza Virus Aerosols
By definition, aerosols are suspensions in air (or in a gas) of solid or liquid particles, small enough that they remain airborne for prolonged periods because of their low settling velocity. For spherical particles of unit density, settling times (for a 3-m fall) for specific diameters are 10 s for 100 μm, 4 min for 20 μm, 17 min for 10 μm, and 62 min for 5 μm; particles with a diameter <3 μm essentially do not settle. Settling times can be further affected by air turbulence (10,11).
The median diameters at which particles exhibit aerosol behavior also correspond to the sizes at which they are efficiently deposited in the lower respiratory tract when inhaled. Particles of >6-μm diameter are trapped increasingly in the upper respiratory tract (12); no substantial deposition in the lower respiratory tract occurs at >20 μm (11,12). Many authors adopt a size cutoff of <5 μm for aerosols. This convenient convention is, however, somewhat arbitrary, because the long settling time and the efficient deposition in the lower respiratory tract are properties that do not appear abruptly at a specific diameter value. Certainly, particles in the micron or submicron range will behave as aerosols, and particles >10–20 μm will settle rapidly, will not be deposited in the lower respiratory tract, and are referred to as large droplets (10–12).
Coughing or sneezing generates a substantial quantity of particles, a large number of which are <5–10 μm in diameter [reviewed in (10)]. In addition, particles expelled by coughing or sneezing rapidly shrink in size by evaporation, thereby increasing the number of particles that behave as aerosols. Particles shrunken by evaporation are referred to as droplet nuclei (10–12). This phenomenon affects particles with a diameter at emission of <20 μm, and complete desiccation would decrease the diameter to a little less than half the initial diameter (10). Droplet nuclei are hygroscopic. When exposed to humid air (as in the lungs), they will swell back. One would expect that inhaled hygroscopic particles would be retained in the lower respiratory tract with greater efficiency, and this hypothesis has been confirmed experimentally (11,12). Aerosols, though heavily diluted, remain airborne and thus can be carried over large distances, which may create a potential for long-range infections. The occurrence of long-range infections is affected by several other factors. These include the infectious dose, the amount of infectious particles produced, the duration of shedding of the infectious agent, and the persistence of the agent in the environment (11). Inferring an absence of aerosols because long-range infections are not frequently observed is incorrect.
Humans acutely infected with influenza A virus have a high virus titer in their respiratory secretions, which makes generation of virus aerosols possible. The viral titer measured in nasopharyngeal washes culminates on approximately day 2 or 3 after infection and can reach up to 107 50% tissue culture infective dose (TCID50)/mL (13,14). The persistence of the infectivity of influenza virus in aerosols has been studied in the laboratory. In experiments that used homogeneous aerosolized influenza virus suspensions (mean diameter 6 μm), virus infectivity (assessed by in vitro culture) at a fixed relative humidity undergoes an exponential decay; this decay is characterized by very low death rate constants, provided that the relative humidity was in the low range of 15%–40% (15,16). These results are consistent with those of an older study (admittedly performed in a more rudimentary manner) in which infectious influenza viruses in an aerosol could be demonstrated for up to 24 h by using infection in mice as a detection method, provided that the relative humidity was 17%−24% (17). In all these studies, the decay of virus infectivity increased rapidly at relative humidity >40%. The increased survival of influenza virus in aerosols at low relative humidity has been suggested as a factor that accounts for the seasonality of influenza (15,16). The sharply increased decay of infectivity at high humidity has also been observed for other enveloped viruses (e.g., measles virus); in contrast, exactly the opposite relationship has been shown for some nonenveloped viruses (e.g., poliovirus) (11,15,16).
Experimental Influenza Infection
Experimental infection studies permit the clear separation of the aerosol route of transmission from transmission by large droplets. Laboratory preparation of homogeneous small particle aerosols free of large droplets is readily achieved (13,18). Conversely, transmission by large droplets without accompanying aerosols can be achieved by intranasal drop inoculation (13).
Influenza infection has been documented by aerosol exposure in the mouse model, the squirrel monkey model, and human volunteers (12,13,17–19). Observations made during experimental infections with human volunteers are particularly interesting and relevant. In studies conducted by Alford and colleagues (18), volunteers were exposed to carefully titrated aerosolized influenza virus suspensions by inhaling 10 L of aerosol through a face mask. The diameter of the aerosol particles was 1 μm–3 μm. Demonstration of infection in participants in the study experiment was achieved by recovery of infectious viruses from throat swabs, taken daily, or by seroconversion, i.e., development of neutralizing antibodies. The use of carefully titrated viral stocks enabled the determination of the minimal infectious dose by aerosol inoculation. For volunteers who lacked detectable neutralizing antibodies at the onset, the 50% human infectious dose (HID50) was 0.6–3.0 TCID50, if one assumes a retention of 60% of the inhaled particles (18). In contrast, the HID50 measured when inoculation was performed by intranasal drops was 127–320 TCID50 (13). Additional data from experiments conducted with aerosolized influenza virus (average diameter 1.5 μm) showed that when a dose of 3 TCID50 was inhaled, ≈1 TCID50 only was deposited in the nose (12). Since the dose deposited in the nose is largely below the minimal dose required by intranasal inoculation, this would indicate that the preferred site of infection initiation during aerosol inoculation is the lower respiratory tract. Another relevant observation is that whereas the clinical symptoms initiated by aerosol inoculation covered the spectrum of symptoms seen in natural infections, the disease observed in study participants infected experimentally by intranasal drops was milder, with a longer incubation time and usually no involvement of the lower respiratory tract (13,20). For safety reasons, this finding led to the adoption of intranasal drop inoculation as the standard procedure in human experimental infections with influenza virus (13).
Additional support for the view that the lower respiratory tract (which is most efficiently reached by the aerosol route) is the preferred site of infection is provided by studies on the use of zanamivir for prophylaxis. In experimental settings, intranasal zanamivir was protective against experimental inoculation with influenza virus in intranasal drops (21). However, in studies on prophylaxis of natural infection, intranasally applied zanamivir was not protective (22), but inhaled zanamivir was significantly protective (22,23). These experiments and observations strongly support the view that many, possibly most, natural influenza infections occur by the aerosol route and that the lower respiratory tract may be the preferred site of initiation of the infection.
Epidemiologic Observations
In natural infections, the postulated modes of transmission have included aerosols, large droplets, and direct contact with secretions or fomites because the virus can remain infectious on nonporous dry surfaces for <48 hours (24). Because in practice completely ruling out contributions of a given mode of transmission is often difficult, the relative contribution of each mode is usually difficult to establish by epidemiologic studies alone. However, a certain number of observations are consistent with and strongly suggestive of an important role for aerosol transmission in natural infections, for example the “explosive nature and simultaneous onset [of disease] in many persons” (9), including in nosocomial outbreaks (25). The often-cited outbreak described by Moser et al. on an airplane with a defective ventilation system is best accounted for by aerosol transmission (26). Even more compelling were the observations made at the Livermore Veterans Administration Hospital during the 1957–58 pandemic. The study group consisted of 209 tuberculous patients confined during their hospitalization to a building with ceiling-mounted UV lights; 396 tuberculous patients hospitalized in other buildings that lacked these lights constituted the control group. Although the study group participants remained confined to the building, they were attended to by the same personnel as the control group, and there were no restrictions on visits from the community. Thus, it was unavoidable at some point that attending personnel and visitors would introduce influenza virus in both groups. During the second wave of the pandemic, the control group and the personnel sustained a robust outbreak of respiratory illness, shown retrospectively by serology to be due to the pandemic strain influenza A (H2N2), whereas the group in the irradiated building remained symptom free. The seroconversion rate to influenza A (H2N2) was 19% in the control group, 18% in personnel, but only 2% in the study group (27,28).
Whereas UV irradiation is highly effective in inactivating viruses in small-particle aerosols, it is ineffective for surface decontamination because of poor surface penetrations. It is also ineffective for large droplets because the germicidal activity sharply decreases as the relative humidity increases (28). Furthermore, because the installation of UV lights was set up in such a way as to decontaminate the upper air of rooms only, large droplets would not have been exposed to UV, whereas aerosols, carried by thermal air mixing, would have been exposed (27,28). So in effect in this study only the aerosol route of infection was blocked, and this step alone achieved near complete protection.
The converse occurrence, blocking only the large droplet and fomites routes in natural infections, can be inferred from the studies on the use of zanamivir for prophylaxis described previously. In experimental settings, intranasally applied zanamivir was protective against an experimental challenge with influenza by intranasal drops (21). However, in studies on prophylaxis of natural disease, intranasal zanamivir was not protective (22), which leads to the conclusion that natural infection can occur efficiently by a route other than large droplets or fomites. As noted above, inhaled zanamivir was significantly protective (22,23).
Discussion and Implications for Infection Control during Influenza A (H5) Pandemic In principle, influenza viruses can be transmitted by 3 routes: aerosols, large droplets, and direct contact with secretions (or with fomites). These 3 routes are not mutually exclusive and, as noted above, may be difficult to disentangle in natural infections.
For the purpose of deciding on the use of N95 respirators in a pandemic, showing that aerosol transmission occurs at appreciable rates is sufficient. Evidence supporting aerosol transmission, reviewed above, appears compelling. Despite the evidence cited in support of aerosol transmission, many guidelines or review articles nevertheless routinely state that “large droplets transmission is thought to be the main mode of influenza transmission” (or similar statements) without providing supporting evidence from either previously published studies or empirical findings. Despite extensive searches, I have not found a study that proves the notion that large-droplets transmission is predominant and that aerosol transmission is negligible (or nonexistent). Reports on many outbreaks suggest that influenza aerosols are rapidly diluted because long-range infections occur most spectacularly in situations of crowding and poor ventilation (25,26). However, even if long-range infections do not readily occur when sufficient ventilation exists, this does not rule out the presence at closer range of infectious particles in the micron or submicron range, against which surgical masks would offer little protection (29,30). Many infection control practitioners have argued that the introduction of large-droplets precautions in institutions has proven sufficient to interrupt influenza outbreaks and therefore that aerosol transmission appears negligible. This evidence is, unfortunately, inconclusive because of several confounding or mitigating factors. First, unless precise laboratory diagnosis is obtained, respiratory syncytial virus outbreaks can be mistaken for influenza outbreaks (9), which would artificially increase the perceived “effectiveness” of large-droplets precautions against influenza. Second, serologic studies are often not conducted, and therefore asymptomatic infections are not documented (among healthcare workers a large fraction of influenza infections are asymptomatic or mistaken for another disease [31]). Third, since we are in an interpandemic period and the viruses currently circulating have been drifting from related strains for decades, we all have partial immunity against these viruses, immunity that is further boosted in vaccinated healthcare workers. It has even been argued that after several decades of circulation the current human influenza viruses are undergoing gradual attenuation (32). Finally, surgical masks (used in large-droplets precautions) do not offer reliable protection against aerosols, but they nevertheless have a partially protective effect, which further confuses the issue (29,30).
In contrast, the situation with a pandemic strain of influenza A (H5) would become only too clear because no one would have any degree of immunity against such a virus, vaccines would not be available for months, and these viruses would likely be highly virulent. Even though efficient human-to-human transmission of the A (H5N1) virus has not yet been observed (by any mode), transmission of influenza A (H5N1) from geese to quails has been demonstrated in the laboratory (33). Thus, even in the current incarnation of A (H5N1), infection by the virus can generate aerosols that are infectious for highly susceptible hosts. As far as we know, 1 of the main blocks to efficient human-to-human transmission of influenza A (H5N1) is the virus’s current preference for specific sialic acid receptors. The current strains still prefer α−2,3–linked sialic acids, which is typical of avian influenza viruses, whereas human influenza viruses bind preferentially to α−2,6–linked sialic acids (34–36). In all likelihood, 1 of the mutations required for influenza A (H5N1) to give rise to a pandemic strain would be to change its receptor affinity to favor the α−2,6–linked sialic acids. For the influenza A (H1N1) pandemic strain of 1918, this change required only 1 or 2 amino acid substitutions (36). Once a highly transmissible strain of influenza A (H5) has arisen, it will likely spread in part by aerosols, like other human influenza viruses.
Recent studies have shown that whereas epithelial cells in the human respiratory tract express predominantly the α−2,6 sialic acid receptor, cells expressing the α−2,3 receptor were detected only occasionally in the upper respiratory tract; however, measurable expression of α−2,3–linked sialic acid receptors was found in some cells in the alveolar epithelium and at the junction of alveolus and terminal bronchiole (35). Binding of influenza A (H5N1) virus can be demonstrated in human tissue sections from the respiratory tract in a distribution corresponding to that of the α−2,3 receptors in the respiratory tract (34,35). This pattern of virus binding correlates well with autopsy findings, which show extensive alveolar damage (34,37), and also correlates well with the observation that recovery of the A (H5N1) virus is much more difficult from nasal swabs than from throat swabs (37). Thus, in the respiratory system the current strains of A (H5N1) appear to infect mostly (perhaps exclusively) the lower respiratory tract. If that is indeed the case, it in turn suggests that human cases of avian influenza were acquired by exposure to an aerosol, since large droplets would not have delivered the virus to the lower respiratory tract. (Another hypothesis might be gastrointestinal infection, followed by viremia and dissemination, but not all patients have gastrointestinal symptoms [37]). Given the strong evidence for aerosol transmission of influenza viruses in general, and the high lethality of the current strains of avian influenza A (H5N1) (37), recommending the use of N95 respirators, not surgical masks, as part of the protective equipment seems rational.
Several infection control guidelines for influenza have recently been published, some specifically aimed at the current strains of A (H5N1), others as part of more comprehensive pandemic plans that address the emergence not only of a pandemic form of A (H5) but also of other types of pandemic influenza viruses. Even though to date human-to-human transmission of A (H5N1) remains very inefficient, the high lethality of the infection and potential for mutations call for prudence. The use of N95 respirators is included in the 2004 recommendations of the Centers for Disease Control and Prevention for healthcare workers who treat patients with known or suspected avian influenza (38). The World Health Organization’s current (April 2006) guidelines for avian influenza recommend the use of airborne precautions when possible, including the use of N95 respirators when entering patients’ rooms (39).
Currently, several pandemic plans differ considerably in their recommendations for infection control precautions and PPE. The current version of the Canadian pandemic plan recommends surgical masks only, disregarding data that support the aerosol transmission of influenza (4). The US pandemic plan (5), as well as the British plans from both the National Health Service (available from http://www.dh.gov.uk/PublicationsAndStatistics/Publications/PublicationsPolicyAndGuidance/ PublicationsPolicyAndGuidanceArticle/fs/en?CONTENT_ID=4121735&chk=Z6kjQY) and the Health Protection Agency (http://www.hpa.org.uk/infections/topics_az/influenza/pandemic/pdfs/HPAPandemicplan.pdf), acknowledges the contribution of aerosols in influenza but curiously recommends surgical masks for routine care; the use of N95 respirators is reserved for protection during “aerosolizing procedures” (5,40). These recommendations fail to recognize that infectious aerosols will also be generated by coughing and sneezing. The Australian Management Plan for Pandemic Influenza (June 2005) recommends N95 respirators for healthcare workers (http://www.health.gov.au/internet/wcms/Publishing.nsf/Content/phd-pandemic-plan.htm), and in France, the Plan gouvernemental de prévention et de lutte «Pandémie grippale»(January 2006) recommends FFP2 respirators (equivalent to N95 respirators) (http://www.splf.org/s/IMG/pdf/plan-grip-janvier06.pdf).Given the scientific evidence that supports the occurrence of aerosol transmission of influenza, carefully reexamining current recommendations for PPE equipment would appear necessary.
<snip> This article appears on the CIDRAP website: http://www.cdc.gov/ncidod/EID/vol12no11/06-0426.htm
The above article should have been cited as being from the journal “Emerging Infectious Diseases,” published 9/26/2006.
I hate to ask, but can you translate the major points of this highly techcnical doucment to bullet points for us not technical ignos. I really read every word and do not unterstand the lingo. I undestood it until about the 4th paragraph, when it start with “Influenza Virus Aerosols “
I read the new article from EID “Review of Aeorsol Transmission of Influenza A Virus” on the CDC website last night. What I remember- Aerosol transmission (as opposed to droplet transmission)of H5N1 more significant than previously thought. Surgical (tie on masks) are insufficient. N95 or better masks should be part of PPE for H5N1 DESPITE some government (US, Canada, England) and health organiation (NHS) recommendations.
Good review article
Suprize: 3M, North and Moldex (respirator manufactures) have all been experiencing record sales over the last 9 months. Most North and 3M P100 & N99 (HEPA)cartidge filters have been on backorder since March 06. There are sources out there but very limited inventories for sure. Same for industrial quantities (liter and gallon) of hand sanitizers. I guess that means someone is prepping.
This is a compelling study that the editors of the EID saw fit to publish. I would like to see some more data on the methodology and effects of atmospheric conditions (humidity, etc) on viability. The most telling part for me is the linkage of the receptor binding and particle size. There is a reason that bioweaponeers wanted to achieve specific particle sizes in their products, and that is to ensure that the weapon powder reaches, and is retained in, the aveolar nodes.
Toroid chamber studies and different modalities of aerosol generation (collision and ultrasonic nebulizer, spinning top, etc.) run against murine and ferret models may have been done, but I don’t have a reference at hand.
Thank you Pixie for bringing this to our attention.
BTW MAV, government agencies at different levels are buying large quantities of N95′s and sanitizer. Some are buying future production through mid 2007 and beyond.
Sarge:
I found a historical site for the 1918 flu the army wrote up afterwards, trying to understand. Not only does humidity play a role according to them, soldiers from states with high humidity did worse overall. This article also explains O’s discussion about one sneeze infecting people thirty feet away in the back of the room on Oprah. I haven’t bought masks, wish I had now, because surgical masks is the majority of hospital stocks. But one lone HCW can’t be expected to buy their own supplies for use in hospitals, therefore, I’m not sure HCW’s will be aware that surgical masks offer no protection. so, now I’m going to e-mail that article to hospital administration and see what happens. Thanks Pixie. Sarge here is url for army document: http://tinyurl.com/pyr7j. It’s worth wading through!
Thank you sir!
H5N1 is known to stabilise in 50–60 degree F water for 4 days and in 33–40 degree F water for up to 30 days.
I have no information on specific freeze/thaw results, but extrapolation follows from the evidence that many negative sense DNA and RNA strains are stable thru a natural freeze/thaw cycle.
Pixie-Quite a find, a hair-raising one at that. Things just get more complex.
Moral of the story-Conduct all business outdoors upwind of hospitals in full sunlight with relative humidity over 40 per cent. Oh, and don’t breathe deeply. Oh, and don’t forget to kiss your ass goodbye.
Let’s see-30 minutes viability and airborne with a 30 mph wind…….
Leo 7-If the conclusions of this study are correct, and the aforementioned deficiencies of the N95 mask discussed on other threads is correct, why should any HCW play this kind of Russsian Roulette?
H5N1 airborne clouding the hallways of the hospital or clinic would be like walking into fields of fire at the Battle of the Somme. It would be stupid, just stupid. Find a warehouse for those crazy enough to come to a hospital with H5N1 and keep the hospital as pristine as possible for the car wrecks, heart attacks, etc.
And - please add to all of that - as reported previously, Canada’s Dr Tam, envoy to the new WHO panel believes that plain ordinary cloth surgical masks will be “just fine” - along with good hand washing!!!! I am still trying to track down her educational bio - my high suspicion is that she was at UWO with Margaret Chen and/or is a pal of noted naysayer Richard Schabas - these ridiculous opinions influence Canadian policy!! arrgghh!! The level of blind ignorance drives me crazy!!!
Applications to a sick room: keep it warm and use a humidifier?
a number of very very interersting things in this artcle! first it claims that sugical masks are inefective,(we did know that,,) but it plays a role in stopping spread!
the anticpation on handwash etc should not overshadow the recomandation on using N95 masks (p2) someone please tell my government…
and very interseting; usage of UV light was very efective! I cant belive they used strong UV-C, if they did, all the patients would become snowblindf with heavy pain. So if it was a veaker UV light, something more related to strong sunlight we have a new tool in our hands to prevent spread inhouse, not in our safe SIP houses, but in entrances, public room, shops etc. And that tool is called tanning lamps! All protection you need is glasses, and with carefull placement( no direct ray into eye view, you could clean massive amounts of air infected with aerosols. Tanning lamps are very common. (if there is elektricity,,)
someone try to dig deeper, and find what kind of UV lamps and rayband mentioned in this experiment?!
bad news is that aerosols seems to be the main route.. 20 minuts is long time to go flying..But then again the sun is our friend,, dark nightimes and winter seems to be a part of this puzzle.
Medical Mmaven at 19:53;
Leo 7-If the conclusions of this study are correct, and the aforementioned deficiencies of the N95 mask discussed on other threads is correct, why should any HCW play this kind of Russsian Roulette?
What “aforementioned deficiency of the N95 mask” are you referring to, please? Which thread is that on?
My reading of the above paper is that N95′s are the way to go, have i missed something?
Urdar- Norway:
I don’t know what uv other than UVC will kill virui. I was puxxled by that reference as well.
I got UVC florescent (sp?) tubes for sterile room and transition room for donning & doffing PPE, but YES keep eyes closed until you put on the goggles that protect against UVC. UVC is also great for water sterilisation as well. Use the crystal U-tubes with either AC or battery power. Some of them are really powerful and can be used for quite large volumes of water, like 50 litre barrels. Much better than filters.
RobT at 21:50-I may have read about the deficiencies of the N95 (and how you really should be employing the N100s) at Current Events. Nothing is 100 per cent. You just don’t want to reapeatedly expose yourself nor expose yourself to situations in which you are walking in a fog of the damn stuff. It’s an odds game and a game of strategy and tactics. And somebody here at fluwiki will “win” the “windblown virus” lottery. (Probably just jinxed myself).
OK MM, understood. I did read alot on CE about masks quite awhile ago, there was a very knowledgeable poster who works in the bio hazard industry. I thought the conclusion of that thread was n95 was good enough for virus particles and aerosol dispersion based on how the n95 filter material traps the particles of that size. I think it is a common misconception that you have to have filter penetration size less than the actual virus size in canister type filters (don’t know about the disposable paper types). Most of the effective action of the canisters is apparently due to the “trapping” effect of the virus getting “stuck” on the filter material as it passes through. So although the N95 material looks like virus size particles could get through, they are effectively trapped by the N95 material.
But your point is well taken, N100 seems better with such a deadly organism. Just the cost is several times higher than the N95′s, and I would want to have alot of them.
Science Teacher – at 20:33 Applications to a sick room: keep it warm and use a humidifier?
SCWAZ: I would worry about “vaporizer” type humidifiers. . . You’d be putting droplets into the air. . . Just a thought. . .
This is why I thought the way I did, from th main article:
“Thus, in the respiratory system the current strains of A (H5N1) appear to infect mostly (perhaps exclusively) the lower respiratory tract. If that is indeed the case, it in turn suggests that human cases of avian influenza were acquired by exposure to an aerosol, since large droplets would not have delivered the virus to the lower respiratory tract.”
Doesn’t it make sense to want to keep the viruses as large droplets by increasing the humidity to a point where they no longer arerosolize as well? If they are allowed to aerosoloize they will spread more quickly in rest of house.
MM @ 1953
Actually, that is just what the small rural hospital that my daughter works at in NM is working on.
They plan to use the HS gym for flu, and keep the hospita; “clean”.
Nice thought,but with the 24+ hour lag between infection and symptoms, how will you tell if the MI that just rolled through the door has a bug incubating ?
MM:
Yes, it is interesting why any sane person will go to work in a hospital when they aren’t being giving the info that will save their own skin. Here’s the problem: They will expect HCW’s to change rigorous habits whenever they finally give the word 5 to 1 has slipped into the perimeter. Usually we gown, glove, mask etc outside the room, go in, do our thing, come out and dispose of gown, glove and mask, wash hands before moving to next patient. This is the procedure and it protects the sick patients, the staff and the visitors, but suddenly we will be expected to do what? Stop doing basic isolation precautions? Do it every 12 patients? Wear the same mask for 12 hours? Stick it under UV light and wear the same one again? Guess I should remember to tote a sharpie with me so I can write my name on it. It just gets worse and worse if hospitals haven’t ordered the equipment. One article at current events said, “HCW’s will have to make do.” After I snorted coffee out my nose I realized she was for real!
The second problem is if 5 to 1 is already in the hospital and we’re still wearing the basic surgical mask, or nothing at all because we don’t know it’s in our hosp. It slips in…that will not be pretty. Even if one hospital is designated the flu house, the patients will already be in every single hospital first unless our warning is way above average. Folks, I just don’t see how this is going to work. Dumping people in a gym, people who are throwing up, incontinent, so dizzy they can’t eat or walk etc is frankly ridiculous. The need for many bathrooms and sinks will be high. How many on this wicki have seen pounds and pounds of vomit and s#@t? Hope that gym—cactus-has a lot of stalls. The caregivers shouldn’t be forced to use the same bathrooms as infected patients. Flu patients should just be sent home. It would be kinder in the long run for everyone.
I wonder how long the virus will hang around in the air? Apparently house dust can take an eternity to settle.
Blue:
Your question is answered in the paper at the top of this thread.
RobT-
Doesn’t it say that virus will essentially never settle.
…”particles with a diameter <3 ìm essentially do not settle.”
I read that the virus is approximately 0.1 micron. That’s less then 3 ìm !
RobT: Check the forum topics for “Masks II”. This where Blue initiated a lively discussion of which masks may or may not be appropriate. I remain opposed to the N95, because of its limitations in filtering, fit, and exhaust (most lack a valve). However, even the disposable N100s, which have superior filtering, better fit, and exhaust valves, are 5 to 10 times the cost of an N95. Apart from that, every mask will be limited by the habits and exposure of the user. Anyway, look for Masks II.
what about nanofilters ? Are valves safe, when a tiny fraction of the air is inhaled, before the valve closes ? (Why) didn’t they already test whether H5N1 transmits by aerosols in mice,ferrets,cats,pigs,
Thanks Dr. Dave…
I like this thread because it keeps the general dicussion on this hot topic new.
Will the N100 be good enough, is naturally the next question, tho?!
RobT : you are corect that UV-C is the thing. But earlier on this forum i presented som data that say that a ordinary tanning lamp do have some C. Its strongly regualated to prevent to much of it, but tanning lamps have all the bands A-B-C in different amounts, their task is to tann, so B is the dominant band. But probably due to technolygy they also have some C, and some of the lamps is illegal since they hav to much of C. I think this article tells us is that in aerosols you dont need that strong UV-C… This will make it practicaly usabel to use small tanning lamps /tubes in cellings or pointing downward to the flor to lower the virus load in a room. Its just like putting sunlight inndors..
for a waiting room in a hospital this could be dealt with by placing sunglasses /protective glasses in a bucket of desinfectant that every one comming in can put on. this could be a backup if there is not enough surgical masks for everyone..
We have to think outside the box, we do have a lot of new technolygy in large quantities they did not have in 1918, lets use it. And dont forget that moderate tanning is god for vitamin D as a preventive for flu and cancer.
…”we do have a lot of new technolygy in large quantities they did not have in 1918, lets use it.”
It has been suggested that we all place something about the “Flu Pandemic Awareness Week” on our MYSPACE ADDRESSES.
THIS WOULD REPRESENT ONE OF THE BEST USES OF OUT MODERN COMMUNICATIONS TECHNOLOGY THAT I CAN THINK OF.
WHAT COULD BE BETTER(I.E. WHAT DO YOU THINK COULD DRAW MORE ATTENTION TO THIS PANDEMIC AWARENESS WEEK?)?
Yes: Let’s use it:)
Myspace.com would have to represent a signigicant readership…from a cross-section of the community.
If it isn’t used it would be a shame.
I just put a picture in my pictures section from the “Awareness Week” thread.
What else could I do?
How should/could I make best use of this technology.?
I would like to think loud even more.. Many months ago a youngster here presented the idea of making masks with UV light instead /or in combination with a more solid washable filter like HEPA. The idea is good, we now know that a product is on its way doing this. Problem is that you cant replace one resource shortage with another, Im thinking of lack of N95 and then batteries.. Ordinary UV bulbs uses a lot of energy. As we know from the alternative energy debate LED is the best. LEDS casings is made of epoxy. Epoxy dont seem the transparent for UV-C so we dont have any desinfecting lamps made with LED. But if an aerosol dont need large amount of C the be cleaned, maybe a homade respirator with UV LEDS may work … this would be very easy to build as a DIY mask…
Wavelengt of UV LEDS are 400nm.. how is that compared to tanning lamps or desinfecting lamps??
http://www.dotlight.de/shop/product_info.php/cPath/217_1_29/products_id/41
If we all start thinking loud enough: it’d be a start!
If you have rechargebal batteries, the sircuit and bulb form the Steripen should work in homemade respirator. The DIY would include a silicon halfmask, a flexibel tube, and a metal tube with lamp, and a hepa filter (from car ventilation, vacum cleaners etc).
the filter should be placed in same way as in gasmaks since it will be a collection point of viruses and should be covered to prevent tuching it.
The lamps shuld be placed inside the metal tube ( a long aluminium should be perfect), then make channels to make air trawel a longer distance radiated in UV light.
Since silicone halfmasks have better fit than the disposables, it will also be a great improvment. This maks will be easer to breath trhu than a filter mask. making it more usable in long timeperiodes. And as long as you have batteries and bulbs,one maks would be plenty for one person during the entire pandemic, you only would need to clean it between usage.
Now if we could use LEDs instead.. that would be brilliant. a verification of the effency is essential for popular use, but when tshtf people will have to improvice a lot I guess.
http://www.backcountryedge.com/products/steripen/steripen.aspx?Affiliate=44
Bronco Bill
Please read Blue @ 4:12 and read the article Pixie @ 14:36
If you think an apology for calling me paranoid when I said these things stated in this report, is in order , a simple “I’m sorry” will do.
My biggest worry is that people may continue shopping and a large number of things until it is too late…suddenly a whole mob of people get sick because there was a calm where people thought it must be over.
This must be how waves occur!
I find this the reason things could sort of seem kind of inevitabl, at times.
I’m saying -it might be a really strategical battle to beat this thing.
(Obviously!)
BB
I re-read my post and it sounded sarcastic. It was not meant that way. I am sincere. Let’s be friends.
I woke up at four this morning with this thought. That TPTB will suppress this study that Pixie found (and like studies) and will squelch the general dessimination of this information. This information widely known (if correct for H5N1) will dash any hopes that anybody will want to go to work. Social distancing and washing hands seems doable and a little dicey, but you have some hope of not being exposed. Dancing, floating aerosols getting into the membranes of your eyes or around the edges of your mask (if you have one) is another thing. The authors of this study went so far as to conjecture that airborne may be the primary means of exposure with influenza A viruses and made a good case for it.
This information is the nail in the coffin for our JIT civilization, if H5N1 behaves the way other influenza A viruses have behaved. And if H5N1 comes in as deadly as “1918″.
Also, I believe JoeW and others made the case some time back that the high attack rate for kids with H5N1 was because of their hyperkinetic, hyperventilating type play outside where the dust particles from faeces would lodge deeply in their lungs, (lower respiratory tract), whereas adults are naturally more sedate in their activity. It could be that it wasn’t even dust particles, but much less, floating aerosols.
MM:
I too have thought about this in many directions. I believe there will be a sense of: it’s the right thing to do (go to work), our country as you know it will end if you don’t go to work etc. In hospitals there will be patients—are we going to abandan them? Therefore your first paragraph is on the money. Also, TPTB know where the problem lies and if the supplies of all types aren’t staged and ready, there will be no announcements until the infection is widespread. This is the only way to keep people where they are:”Folks you’re already contaminated, let’s do the best we can.” etc.
Also this aerolized form of contamination can’t really be stopped. Eyes are mucous sponges, and you can’t mouth breathe either. Kids will never wear mask, and keep eyes totally enclosed either. So, if you don’t have the right mask your eyes most be totally covered,and you can’t ever mouth breathe either. No one is this perfect. Hospitals will indeed be pest houses. SIP is survival especially for kids.
I am concerned that critical workers, public health, town officials, and first responders, along with HCW’s, are unaware of this information. I have also heard that many of these critical people are depending on their states to provide them with the proper PPE and other equipment should a pandemic hit. I think that, in light of these findings, local authorities should move now to obtain the supplies they need.
Also, to add to this debate, I am aware that N95′s may not be fully effective. However, Niman has a theory that those we are seeing in the present clusters that have received a lower “dose,” or a lower viral load of the virus are the ones that recover (typically those we see later in the chain of transmission). There are, of course, other factors affecting this. But if he is right, or even partly right, then the use of proper PPE could lessen an individual’s exposure and thus their viral load (at least it seems to make sense that it might). If it gives these critical workers who need to be out and about during a pandemic the edge in surviving, then it the “lower viral load” theory should be considered seriously at least.
While the article posted above used theoretical and laboratory models to arrive at its conclusions, it seems likely that H5N1 is now airborne within some of the Indonesian clusters (their top virologist suspects that). For those people who have the type of casual contact with infected cases as we are seeing now in Indonesia, this PPE may prove effective. I really don’t know what we can recommend to the HCW’s who will be dealing with the most serious cases.
Good post Pixie, you give us some hope.
So, one little virus floating through an N95 won’t kill you: that is the question!(?)
Interesting about kids running aroung leading to deeper ingestion!
Pixie:
Hopeful, but not in the case of a hospital where the viral load will be stupendous. This also doesn’t bode well for a designated flu site either. Imagine a gym full of people with inadequate masks or eyewear available. Flu tents would be healthier just like in 1918. It comes down to the numbers of infected in a certain area or building. Large worksite buildings odds go up—small buildings with small numbers of people better odds.
This is good for work-good for having to go in some public areas—no help for hospitals or any place that isn’t properly ventilated where flu patients congregate.
The UV-c light discussion may be important. Older nurses report that UV lights used to be placed over the entrance to TB patients rooms back in the day. Back then they had designated TB admission rooms but they have disappeared in my experience. I don’t know why—if I have time I will google it. MAV in Col do you know why they stopped using the UV lights?
when it depends on viral load, then won’t aerosol-infection cause less serious disease than droplet-infection ? I assume with aerosols the virus load is diluted much more than with droplets.
?_
easy with the easy conclusions.. (also count for me ;-) That eaerosols is a way of infection is clear. What is not clear is that this means that “it will crawl into your eyes, ears or your under your toenail”.. Did not the study antcipate the differneces between upper and lover airways in conjunction with droplets sice? Yes. Not a single word about faceshields being inadekvate. I am not saying that a pair of skigoogles dont belong in your preps,(they are in mine) but this is still not “a virus from outer space”
Leo7 – at 11:15 - Yes, I came to the same conclusion. I hope this news may be hopeful to some, and that they will be prudent enough to act on it while they can and place their orders now.
Leo, I don’t know what we will do about the HCW’s. I have a friend who is a nurse, not working but staying at home for the moment with her young children. I told her yesterday that I thought she might not want to send in her license renewal, and she responded that she just had. She’s a bit worried about being pressed into service, as I am sure many HCW’s will be similarly worried, particularly those like my friend with young (and suseptible) children. But doctors and nurses did go to work in 1918. However, as you say some of their old practices like tenting may still prove to be more effective, and perhaps more practical, than the limits that our JIT supply system leaves us with. And I wonder if some of our retired physcians and nurses might not prove to be more effective than those who’ve come to rely on the niceties of our modern world.
Pixie:
Self preservation took over and I ordered my own masks, eye shields etc. Only hope they arrive on time. I will end up sharing with my co-workers in all likelihood. There are lots of nurses waiting to renew their licenses which extends into November before occuring a late fee. With late fee sometime in late Dec. I don’t believe this will work since states intend to call up the retired or at least appeal to them to do so. People will go—many unaware of the risks. I think this is grossly unfair. Sometimes I wonder why Im going in, because I do know. I threw a barbeque/beerbust last weekend, lots of nurses, paramedics, docs, and police here. One paramedic said, he was unsure whether he would attempt intubation in the field on patients with flu symptoms. I could tell the verbal statement made him uncomfortable because he’s a great paramedic for over ten years.
I told him I understood. HCW’s do talk about it and most are frustrated because the institutions they work for aren’t really preparing. This is an emotional trap that is easily exploited. My thoughts are: by the time the official warning goes out-HCW’s will already be exposed if those 3 week models are correct and the airlines remain in the air. Almost everyone agreed (at the party) if the airlines shut down-this is their alert signal. TPTB surely know this…therefore the planes will fly.
the idea of using any large halls to gather people is cracy. I realy dont hope you have any of this in plans officilay. Here the national plan put weight on NOT using any halls. Hotels, elders care institutions and and tents in front of hospitals is what here is planned, please tell your people i charge that this was one of most impotant lessons from spanflu. Not only the virus spreads, but also the pnaumonias.
Please keep saying that, Urdar-Norge, because at present our plans for pandemic mitigation are based on hospitals and large halls. You cannot repeat your message too many times.
Urdar-Norge:
My city is spread out with 300,000 people! 4 big hospitals all usually full. I agree with you. People should stay home and if they get sick treat at home. But that is alot like back in the day when they locked up the well in a home with the sick—a death sentence for most. People want somewhere to dump the sick, so the well won’t have to look at them. So they talk about tent cities and gyms etc. Tent cities might function but family members will have to nurse their own—there won’t be enough volunteers or others to do it. Here in the USA the state plans lull the clueless back to sleep. When they wake up the one percenters that (us) will need ear plugs!
Influenza virus will be airborne in two forms. Aerosolized viral particles and virus contained within droplets of “other” material. The ones we should be most concerned about are the smaller, lighter aerosolized particles because (A) they will stay airborne longer (B) they penetrate deeper into the lower respiratory tract where disease tranmission is most effective. Masks and respirator cartidges are just filters. They are only capable of filtering what goes through them (ie require air tight face seal). They are subject to functional limitations (ie air presure gradients, particulate concentrations etc)With a lethal infective agent there is NO place for anything less than HEPA (ie P100/N100 etc) filtration when exposed to the disease. The use of N95′s or “surgical tie on masks” etc, or reusing, disinfecting etc or use of other untested methods of are all potentially lethal breaches of STANDARD procedures. All filtration medium is subject to degredation. Moisture, either from high RH environments or respiratory condensation will rapidly degrade filter materials. Exhalation ports (valves) reduce this effect. Attempting to disinfect disposable filters with liquids will probably not remove viral particulate matter from and will undoubtedly alter the microscopic structure of the mask and would NOT be advisable.
Also, although face shields would be better than nothing, sealing, non-vented goggle type eye protection would be superior.
To my knowledge, UV radiation is very effective on “naked” microbes like aerosolized virii which stay airborne and closer to the ceiling mounted lights but probably would be ineffective against the hardy, waxy cell wall of heavy TB droplets which would not remain airborne for long (short UV exposure).
Wiki HEPA page→ http://tinyurl.com/ee5gu NIOSH site→ http://tinyurl.com/rdvst
bump
Mav in Colorado @ 13:46
Instad of trying to diinfect filters and other supplies with liquid disinfectant, what do you think about either placing it in a plastic bag and laying it in the sun or hanging in a well lit room for 2 weeks to allow to dry and disinfect over time to be reused?
prepmaniac- reusing disposable PPE is NOT part of my planning. I suppose if you hung them up out in the sunshine for 2 MONTHS the UV and dessication would eventually render virus inactive. I would consider using a used mask IF I was being exposed with nothing else available for PPE.
A pair of P100 cartidges for a half or full mask are about $4.25 and should last at least one day of continuous exposure. Harder to get now but still worth the consideration and effort. With the background threat of NBC terrorism increasing by the day, depending on your location, you might make the investment and go with a half or full respirator with NBC canisters added to your P100 cartridge preps.
Remember used PPE = contaminated (infectious) PPE Dispose of (handle) with extreme caution!
Closed to maintain Forum speed.