Although a third American farmworker has been infected with bird flu, heightening concerns about an outbreak among dairy cattle that was first identified in March, experts insist the threat to the general public remains low.
However, the worker is the first in this outbreak to display respiratory symptoms, including a cough, sore throat and watery eyes, which generally increase the likelihood of transmission to other people, reports The New York Times.
The other two people had only severe eye infections, possibly because of exposure to contaminated milk.
All three individuals had direct exposure to dairy cows, and so far none has spread the virus to other people, said Dr Nirav Shah, principal deputy director of the US Centres for Disease Control and Prevention (CDC).
“That suggests that the virus (H5N1), has not acquired the ability to spread among people and that the threat to the general public remains low.
“This newest case does not change the CDC’s H5N1 influenza risk assessment level for the general public. We should remain alert, not be alarmed.”
But the case does highlight the ongoing risk to farm workers.
It is the second in Michigan, but the affected person worked on a different farm from the worker diagnosed last week. All three cases have so far have been treated with the antiviral medication oseltamivir, sometimes marketed as Tamiflu.
Rick Bright, the chief executive of Bright Global Health, a consulting company that focuses on improving responses to public health emergencies, said federal officials are “months behind sharing virus sequence data”.
“This is how pandemics start,” he said.
Shah said new flu viruses often provoke respiratory symptoms without further spread to other people.
Different route
This latest patient may have had different symptoms because of the exposure dose, a different exposure route, predisposing genetic or medical factors or a combination of those attributes, said Angela Rasmussen, a research scientist at the Vaccine and Infectious Disease Organisation at the University of Saskatchewan in Canada.
She added that gaining more information about how the person was infected and about whether the virus has evolved to infect people more readily was crucial.
Genetic analysis of the virus infecting the worker may be difficult because the amount obtained from the patient was very low.
“But every time the virus is able to replicate in a person, there is potential for it to adapt to humans and gain molecular features for replication in the respiratory tract and to spread person-to-person,” said Seema Lakdawala, a virologist at Emory University in Atlanta.
Officials 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 it was budgeting $824m in new funding to quickly detect cases in poultry and livestock. It is also launching a voluntary programme for producers to test bulk milk, enabling them to transport virus-free herds across state lines without having to test individual cows.
Federal officials could be doing more to protect farm workers and the public, experts said.
“Vaccines from the national stockpile should be released for veterinarians and dairy farm workers willing to take it,”. Lakdawala said. “We have an opportunity to reduce human infections and we need to do it now.”
The New York Times article – Bird Flu Has Infected a Third US Farmworker(Restricted access)
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