Officials in California have declared a state of emergency over the spread of bird flu, which is ravaging dairy cows in the state and causing sporadic illness in people in the US.
Here’s what you need to know.
How did bird flu spread in the US?
The virus, also known as Type A H5N, has been spreading among wild birds, commercial poultry and many mammal species for years. The disease was first found in American dairy cattle in March. Since then, bird flu has been confirmed in at least 866 flocks in 16 states.
According to the US Centers for Disease Control and Prevention (CDC), more than sixty people in eight states have been infected, with mostly mild illnesses. Almost all of these were farm workers who were directly exposed to infected dairy cattle or poultry.
One person in Louisiana has been hospitalized with the nation’s first known serious illness caused by the virus, health officials said this week. That patient was infected through a herd in the backyard.
In addition to direct contact with farm animals and wild birds, the H5N1 virus can be spread through raw milk. Pasteurized milk is safe to drink because the heat treatment kills the virus, according to the U.S. Food and Drug Administration (FDA).
There have been no reports of person-to-person transmission.
How did it spread in California?
California is the largest milk-producing state in the U.S., and three-quarters of the nation’s infected herds, about 650, are in the state.
The state has been looking for bird flu in large milk tanks during processing, and the virus was discovered earlier this month at four Southern California dairy farms after being found in the state’s Central Valley since August.
The detection at Southern California farms made clear that the state needed “a shift from regional containment to statewide monitoring and response,” California Governor Gavin Newsom said in his emergency declaration.
What does the emergency declaration do?
The declaration allows the state to better position state personnel and supplies to respond to the outbreak, Newsom said.
“This proclamation is a targeted action to ensure government agencies have the resources and flexibility they need to quickly respond to this outbreak,” Newsom said in a statement.
What is the risk to the public?
CDC officials emphasized again this week that the virus currently poses a low risk to the general public.
But the case of severe illness in the US this week shows that while previous cases mainly caused redness of the eyes, the virus could pose a danger to some people.
The Louisiana patient, who is over 65 years old and had underlying medical problems, is in critical condition. Few details have been released, but officials said the person developed severe respiratory symptoms after exposure to a flock of sick birds in the backyard. That makes it the first confirmed U.S. infection linked to backyard birds, the CDC said. Tests showed that the strain that caused the person’s illness is found in wild birds, but not in cattle.
Last month, health officials in Canada reported that a teenager in British Columbia had been hospitalized with a serious case of bird flu, also the strain of the virus found in wild birds.
It’s possible that as more people become infected, more severe illness will occur, said Angela Rasmussen, a virus expert at the University of Saskatchewan in Canada.
“I assume that any H5N1 virus has the potential to be very serious and deadly,” Rasmussen said.
What are other reasons experts are concerned?
Although there have been no reports of person-to-person transmission and no signs that the virus has changed and can spread more easily among people, experts warn that flu viruses are constantly mutating and that small genetic changes can change the outlook.
Flu experts say it’s too early to tell what trajectory the outbreak might take. “The completely unsatisfactory answer will be: I don’t think we know yet,” said Richard Webby, a flu expert at St Jude Children’s Research Hospital.