Avian flu is a topic we've been covering for a while now. Although people often think of influenza as a fairly harmless illness, compared to, say, ebola or lassa fever, it has the potential to cause far greater loss of life. Every so often a new virus strain emerges and jumps from its animal reservoir into the human population. This can then spread round the world rapidly, and as it's a new virus strain, no one has any immunity to it. About every 30 years, on average, a particularly virulent strain will emerge, resulting in a pandemic.
The strain that's currently getting everyone so worked up is called H5N1, and first appeared in wild birds in south east Asia. Wild birds infected poultry, and from there humans have been infected. Worryingly, H5N1 is very pathogenic, and mortality rates from the virus are around 50% for known cases. To put that in context, the 1918 pandemic that killed up to 50 million people had a mortality rate of only 2%! Luckily for the world at large, human-human infection does not seem to have happened outside of one or two isolated cases.
It is crossing the world though. Outbreaks of H5N1 are now suspected in Turkey and Romania, and the EU has banned imports of live birds and feathers from Turkey. In 2003 H7N7, a strain that did not infect humans, erupted in the Netherlands, resulting in the culling of millions of poultry.
Fears about H5N1 continue to grow amongst policy makers, no doubt spurred on by dire warnings from scientists and health officials. A new report commissioned by the US government suggests that the world's hyperpower is terribly unprepared for an outbreak:
The 381-page draft plan, leaked by health officials who claim that it contains fundamental failures, predicts that a full-scale outbreak could kill as many as 1.9 million Americans and put 8.5 million in hospital at a cost of more than $450 billion (£256 billion).
Hospitals would quickly become overwhelmed, riots would break out at vaccine clinics, civil unrest would sweep the country, and power and food would be in short supply, according to the plan, which has been years in the making. It calls for quarantine and travel restrictions but concedes that those measures “are unlikely to delay introduction of pandemic disease into the US by more than a month or two”.
Work is underway on developing vaccines to immunize against H5N1 infection, although reports from the London Times suggest that foot-dragging by the UK government is holding up that development. The NY Times has news on how other countries across the globe are preparing for possible outbreaks.
H5N1 might be the strain that everyone is excited about right now, but it's not the only influenza vrus that's been under the microscope, so to speak. Scientists have recently completed a study looking at the genetic sequence of influenza viruses responsible for infections in the NY area between 1999 and 2004. The study found that three separate substrains of H3N2 were infecting patients concurrently, and that the influenza virus is capable of reshuffling its genome, giving it an advantage against its host immune system. Indeed, 2003/2004 flu vaccine is believed to have provided less than optimal protection as a result of the virus' evolution.
Lastly, work has been underway on H1N1, the culprit behind the 1918 pandemic that killed more people than WWI. Using samples recovered from a flu victim found in the Alaskan permafrost, a team lead by Jeffery Taubenberger at the Armed Forces Institute of Pathology in Rockville, MD, have succeeded in sequencing the genome of H1N1*:
A total of ten amino acid changes in the polymerase proteins consistently differentiate the 1918 and subsequent human influenza virus sequences from avian virus sequences. Notably, a number of the same changes have been found in recently circulating, highly pathogenic H5N1 viruses that have caused illness and death in humans and are feared to be the precursors of a new influenza pandemic.
Not content with just knowing its makeup, researchers at the CDC in Atlanta used this sequence to reconstruct H1N1*, allowing us a detailed look at just how this virus ravages its victims. Lets just hope it doesn't get loose!