CHINA : Despite its horrific impact on West Africa, Ebola – since it is not an `airborne virus’ – is unlikely to spark the next great pandemic. None of which is to sell the impact of this virus short. If it is not contained soon, it could wreak considerable havoc around the globe – particularly in the developing world.
For almost two decades the H5N1 virus has been on the radar screen – ever since it caused an outbreak in Hong Kong in 1997 (18 human infections, 6 fatal). Massive poultry culls seemingly sent the virus packing – but it reappeared in Vietnam in 2003 – having apparently been circulating unnoticed in wild birds and poultry in China.
For nearly a decade, the H5N1 virus captured the bulk of our attentions. Yes, there were `other’ avian strains out there of interest – H7s and H9s – but none produced the kind of dramatic high mortality in humans that this HPAI H5N1 strain did.
Instead of producing mild respiratory symptoms and conjunctivitis – which is what we saw with other H7 avian viruses – this reassortant was killing up to 30% of hospitalized cases.
Either virus would be devastating were they to gain the ability to spread efficiently between humans. For now, infection comes primarily from direct exposure to infected poultry, and secondary transmission remains rare. Neither virus has evolved to the point of becoming an imminent human pandemic threat.
But these viruses – and others recently arrived on the scene – continue to mutate, reassort, and evolve. They roll the genetic dice millions of times each day – and even though successful mutations are rare – with that many opportunities the odds say they will eventually find the right combinaton.
One that makes the virus more `biologically fit’.
Diversity of circulating H5N1 Clades – Credit WHO
Until a couple of years ago, China was very circumspect in regards to their`avian flu problem’. Even when we heard of mass poultry die offs or culls, or when migratory birds flying out of China were often found to be infected, China rarely acknowledge human – or poultry – infections with H5N1.
In the past two years, after a decade of really only watching H5N1, we’ve seen an unprecedented explosion in new subtypes of avian flu appearing in China.
H6N1 (in Taiwan)
The H10N8 virus emerged last winter, and infected (and killed) three people in China. H5N6 – while only infecting one person (that we know of) – has spread quickly across China and into Vietnam since it first appeared last April.
All of which brings us to 5 OIE reports filed late last week by China informing the international community of two `new’ H5 virus detections, and a significant number of H5N1, H5N2 and H5N6 detections among poultry across the country.