- The case of the vanishing pandemic: Deadly bird flu flies the coop in the US
- Scientists puzzled by disappearance, but think lack of vaccination may be key.
In November of 2014, a highly pathogenic strain of bird flu derived from Eurasia called H5N2 popped up in North America—in a Canadian turkey farm east of Vancouver, to be exact. From there, the virus quickly spread and mutated into new varieties, including H5N1, fanning fears it would vault to humans and cause a deadly pandemic. By March of 2015, it and its kin had swooped into 15 US states, causing 248 outbreaks in domestic birds and $5 billion worth of damages to poultry operations.Then, it vanished.
…In a controversial twist, it may mean that bird vaccines, which aren't used in the US, are boosting potential pandemic flu viruses in other places of the world.
Webster and his team didn’t find any of the high-pathogenic H5N2 viruses in the wild US birds, nor any of the virus’ hybrid offspring… wild water fowl in the US had not tested positive for a highly pathogenic H5N-something virus once in the 43 years prior to the outbreak.
Webster hypothesizes that the garden-variety flu viruses essentially elbow out the highly pathogenic ones. So, when those nasty varieties move into wild bird populations, they don’t stay long.
But, if Webster is right, it raises more questions about why and how some places, particularly in Asia, continually see the spread and maintenance of those highly pathogenic flu viruses in wild birds. And this is where vaccines come in to Webster’s hypothesis.
Flu vaccines for domestic birds don’t always completely block the virus. In a small number of vaccinated birds, highly pathogenic flu viruses can still get a foot in the door and cause an infection. But those infections are mild, more like seasonal flus—unnoticeable to poultry farmers and perhaps even the bird. However, those domestic birds will still poop and shed massive amounts of highly pathogenic viruses. And those viruses can then continually be picked up by wild birds.
In many places in Asia, poultry farmers clamor for vaccinations. But, in the US and Europe, which don’t see the same levels of highly pathogenic viruses, vaccines aren’t regularly used.
Instead, the US Department of Agriculture adopted a system of monitoring, quarantining, and culling. It’s expensive, Webster noted, but it may be the best way to squash a potential pandemic.