Bird Flu Is Back in the US. No One Knows What Comes Next

The virus in all three was what is known as highly pathogenic—meaning it could cause fast-moving, fatal disease in other bird species, such as poultry, though it was not making the ducks ill.Three birds out of the millions that American hunters shoot each year might seem like nothing—but the findings have sent a ripple of disquiet through the community of scientists who monitor animal diseases. Before Covid arrived, avian flu was considered the disease most likely to cause a transnational outbreak.It is far too soon to say whether the arrival of this virus in the US is a blip, an imminent danger to agriculture, or a zoonotic pathogen probing for a path to attack humanity. (Those are short for proteins that let the virus infect cells.) Just within the As, there are almost 200 subtypes; a few affect humans, but almost all of them can infect birds.Lesson Two: For a long time, scientists thought humans were in little danger from all those other flu strains. (A prominent poultry researcher once called it “chicken Ebola.”)To sum all that up (there will not be a quiz): The flu found in the Carolinas is an H5N1, meaning it is of the subtype that normally infects birds but in the past has sickened people. And, to make matters worse, it represents just one instance of a remarkable amount of highly pathogenic H5N1 showing up in the world right now.Last year, the World Organization for Animal Health (known by its French acronym, OIE) estimated that between May 1 and November 1, 41 countries experienced outbreaks of highly pathogenic bird flu, with 16,000 isolations of the virus reported just in October. Fifteen countries also reported outbreaks between October and December.Occasional isolations of avian flu in wild birds are not unusual, but last fall high-path H5N1 began erupting in the United Kingdom with extraordinary intensity. In December, the UK’s chief veterinary officer called the occurrence of bird flu there “phenomenal,” saying the strain had spread to the largest number of farm properties ever seen.At almost the same moment, Dutch authorities were ordering the slaughter of hundreds of thousands of poultry on farms in the country. That is the same flyway that crosses over the Carolinas, where the virus-carrying ducks were caught—and also over the more than 1 billion chickens grown each year in Georgia, the most poultry-dense state in the US.Because this flu is highly pathogenic, the challenge is that there is no time for mitigation once it arrives in a flock.