- More than 3 million hens will be slaughtered in Iowa to contain a bird flu outbreak that's been spreading through the West and Midwest since last December.
- So far, the H5N2 strain of the disease has been detected in wild birds and at poultry farms in 16 states.
- Health officials are concerned because animal outbreaks can infect humans, leading to a flu pandemic.
- The current outbreaks, however, don't seem to involve H5N1, the bird flu strain most dangerous to humans.
16 states so far have cases of bird flu
Since December, cases of bird flu have been found in wild birds, backyard poultry, and commercial poultry in 16 states, including California, Iowa, Idaho, Oregon, Washington, and Wisconsin, according to the Centers for Disease Control and Prevention.
Iowa has been hit particularly hard. There, 3 million hens will be slaughtered in order to contain the outbreak, and foreign buyers of live birds and eggs have already imposed trade restrictions.
Bird flu has only rarely made people sick
Like humans, birds — including chickens, ducks, and other wild poultry— get sick with the flu sometimes. When they do, bird flu virus can spread easily among them through respiratory secretions (like spit from a sneeze) and feces, reaching epidemic proportions very quickly.
The reason experts worry so much about bird flu is because it's an easily transmissible virus, and some strains have managed to infect humans — with deadly outcomes.
So far, bird flu has only rarely made people sick. And most human cases involved very close contact with infected birds, rather than spreading from one person to another.
But there's the concern whenever the virus surfaces that it could makes the leap into humans and mutate to become more easily passed among people, leading to a pandemic. As Matthew Weaver at the Guardian notes, "Pandemics have occurred every 20 to 30 years, but it has been almost 40 years since the last one happened."
Of all the bird flu strains, H5N1 is the one public health experts worry about the most. It's believed to be the most dangerous form of bird flu and has caused serious outbreaks, mostly among animals in Asia and the Middle East, as well as some 650 human cases since 2003.
Most human cases of H5N1 virus have turned up in people who had direct contact with infected animals in Asia. Sixty percent of those infected later died.
The CDC considers the risk to humans "low"
The chance that these outbreaks at the nation's farms will spread to humans is "low at this time," CDC officer Alicia Fry stated at a press conference today.
That's because the outbreaks here involve strains of the virus that haven't been deadly in humans.
Fry also added, "While we are cautiously optimistic that there will not be human cases, we must be prepared for that possibility." Flu outbreaks can take people by surprise, and there's still a lot we don't know about bird flu and how it spreads. The WHO has long warned that a pandemic could start off with just the scenario we're seeing now: infected birds on a farm.
So officials have also been working to contain the virus's spread, killing off birds that may have been infected, including those in Iowa — the worst affected state. The USDA and CDC are also studying the virus and working on a potential vaccine for this strain.
For now, health officials recommend avoiding wild birds and contact with domestic birds that seem to be sick.