With Thanksgiving coming this week, it seems like a good time to talk a little bit about the impending apocalypse, delivered unto us by poultry. In other words: avian influenza.
Avian influenza (AI) is a virus with two main biological components – the hemagglutinin (which binds the virus to a host cell ) and neuraminidase (which allows it to be released from a cell ). So when you hear H5N1 – the numbers refer to specific strains of hemagglutinin and neuraminidase that vary in their pathogenicity. Wild aquatic birds (ducks, geese, gulls and shorebirds) are the natural host of avian influenza. It is very common for these birds to have one (or more) strains of AI over the course of a year – they don’t die and barely even have symptoms. “Low pathogenicity” AI strains are no big deal to aquatic birds and when they can spread to poultry, the chickens and turkeys have mild symptoms. On the other hand, “high pathogenicity” AI strains can arise from low pathogenicity strains from within domesticated poultry and are highly lethal to chickens and turkeys. The strains most likely to do this are H5 and H7 – these are the strains you hear about in the news that result in massive poultry culls. These strains can spread back to wild aquatic birds, who – if you’re a hunter or birdwatcher know – migrate across entire continents in large flocks. These strains can also spread to humans who are in direct contact with sick, high pathogenicity poultry.
SO FAR, avian flu virus has rarely (but not never) been transmitted from human to human (i.e., airborne). This is good, because the death rate of one H7N9 AI strain in China in 2013 was around 33%. Slightly worryingly, this strain still persists there – mutating all the while. The doomsday scenario that the WHO and CDC are worried about is a high pathogenicity strain mutating such that it becomes airborne – a scenario that could put tens of millions of people at risk. I suppose a secondary doomsday scenario would be high pathogenicity AI infected ducks dropping deadly high pathogenicity AI duck turds on our heads as they fly across the country. (Did I just come up with the plot for a horror/comedy movie? I await your call, Hollywood.) The USDA is monitoring cases of high pathogenicity AI in wild North American waterfowl and they’re specifically watching an H5 strain that showed up here last year.
The internet has tons more info if you want to read more or freak yourself out. I do kind of feel like a jerk for bringing this up as we’re all headed to airports and then to our families. At least there is some “good” news – no shortage of turkey! Happy Turkey Day! (gulp)