Just prior to the 1957 and 1968 pandemics, does anyone know if there were direct bird to human transmissions and how lethal they were? I would like to compare that information with H5N1.
The 1957 and 68 viruses were reassortants, where the existing circulating human flu strain picked up gene segments from avian viruses.
In 1957, the existing H1N1 picked up a new HA and NA and PB1 gene, becoming H2N2.
In 1968, H2N2 picked up a new HA and PB1, becoming H3N2.
Bird to human transmission was not an issue in the run-up to both pandemics.
The answer to what you might be trying to find out probably still lies with 1918. The 1918 pandemic, with H1N1 is the earliest documented instance of an avian virus infecting humans. Scientists at the NIH working on pre-1918 samples have identified a number of influenza HA’s, and they were all H3. Our hope is that if they find samples from the first wave, that may tell us more about the transition from b2h, if that was indeed what happened, or whatever other mechanisms were responsible for the appearance of the 1918 virus.
Thanks anon_22 for the reply.
I was wondering (prior to the reassortment and before the pandemic began) if there were any human deaths like H5N1 is now causing. Because if there weren’t any, then could this indicate that H5N1 is more likely to cause a severe pandemic rather than a mild one?
K from Mi – at 16:46
I was wondering (prior to the reassortment and before the pandemic began) if there were any human deaths like H5N1 is now causing. Because if there weren’t any, then could this indicate that H5N1 is more likely to cause a severe pandemic rather than a mild one?
No. Or at least there is no historical data for that.
However, very very recently, all of 5 days ago, ie Nov 7 2006, Taubenberger’s team at the NIH working on tissue samples from patients in London, have identified 3 cases from January-July 1918 that tested positive for influenza RNA. (I also posted about that with more details on the News Thread.)
They haven’t characterized it yet, but if this was H1, that would be the place to look for the answer to not just your question but a whole lot of questions about how influenza viruses switch hosts. Not just switching to cause sporadic cases, but to establish a whole new lineage in a new species.
That doesn’t answer your question, of course.
We don’t know that H5N1 is likely to cause a severe pandemic. But we do know that there is no scientific basis to support the widely circulated notion that the mortality would drop if it does cause a pandemic. This has recently been finally and officially stated by scientists on the WHO Pandemic Task Force, reported on the WHO Report On Influenza Research thread.
In addition, H5N1 has done many things that other influenza A viruses have not been able to do, such as infecting novel species like tigers, where the virus was immediately transmissible from tiger to tiger, and the mortality was 100%. Or being able to cause such severe systemic disease in chickens that you get 100% mortality within a few hours of inoculation, something that spooked even veteran virologists like Robert Webster, who calls it the worst virus he has ever seen in his whole life.