A third farm worker in the United States has been found to be infected with bird flu, raising concerns about an outbreak among dairy cattle first identified in March.
The worker is the first in this outbreak to have respiratory symptoms, including cough, sore throat and watery eyes, which generally increase the likelihood of transmission to other people, federal officials said Thursday.
The other two people only had serious eye infections, possibly due to exposure to contaminated milk.
All three individuals had direct exposure to dairy cows and so far none have transmitted the virus to others, Dr. Nirav Shah, principal deputy director of the Centers for Disease Control and Prevention, said at a news conference.
That suggests that the virus, called H5N1, has not acquired the ability to spread between people and that the threat to the general public remains low, Dr. Shah said.
“This most recent case does not change CDC’s H5N1 influenza risk assessment level for the general public,” he added. “We must remain alert, not alarmed.”
But the case does highlight the ongoing risk to farmworkers, Dr. Shah said: “Our top priority now in this response is to protect the health of farmworkers.”
This case is the second in Michigan, but the individual worked on a different farm than the worker diagnosed last week. The three people infected so far have been treated with the antiviral drug oseltamivir, sometimes marketed as Tamiflu, officials said.
There were some other details. available, disappointing some experts.
“There is no excuse for the lack of testing, transparency and trust,” said Rick Bright, CEO of Bright Global Health, a consulting company that focuses on improving responses to public health emergencies.
He noted that federal officials are “months late in sharing virus sequence data.”
“This is how pandemics begin,” he said.
The identification of a third case is not surprising because farm workers interact closely with dairy cows, experts said. New flu viruses often cause respiratory symptoms without spreading to other people, Dr. Shah said.
This latter patient may have had different symptoms due to exposure dose, a different exposure route, predisposing medical or genetic factors or a combination of those attributes, said Angela Rasmussen, a research scientist at the University’s Vaccine and Infectious Diseases Organization. of Saskatchewan. in Canada.
Still, it’s crucial to get more information about how the person was infected and whether the virus has evolved to infect people more easily, he said.
Genetic analysis of the virus infecting the worker can be difficult because the amount obtained from the patient was very low.
“But whenever the virus is able to replicate in a person, there is a possibility that it adapts to humans and acquires molecular characteristics to replicate in the respiratory tract and spread from person to person,” said Seema Lakdawala, a virologist. at Emory University in Atlanta.
Authorities are monitoring about 350 people who may have been exposed, about 220 of them in Michigan alone. So far, relatively few farmworkers, about 40, have consented to testing.
The Agriculture Department announced Thursday that it was setting aside $824 million in new funding to quickly detect cases in poultry and livestock. The department is also starting a voluntary program for producers to test bulk milk, which will allow them to transport virus-free herds across state lines without having to test individual cows.
Federal investigators completed their analysis of 109 beef samples and found viruses in only one, as reported last week, officials said at the briefing.
Experts said federal officials could be doing more to protect farmworkers and the public.
“Vaccines from the national stockpile should be given to veterinarians and dairy farm workers who are willing to receive them,” Dr. Lakdawala said. “We have the opportunity to reduce human infections and we must do it now.”