The Centers for Disease Control and Prevention is recommending several measures to reduce the risk of farmworkers being infected with bird flu as well as testing of poultry and dairy employees who may have been exposed to the H5N1 virus, even if they do not show symptoms of illness.
While continuing to say the risk to the general public remains low, CDC Deputy Director Nirav Shah told reporters Thursday that the agency wants “to focus on the highest-exposure tasks in poultry and dairy operations, ultimately to reduce the risk of infection.”
The testing recommendation focuses "on workers who were exposed and who do not have symptoms, particularly those who were not wearing appropriate PPE," Shah said. CDC also is urging the use of Tamiflu for exposed, asymptomatic workers, and focusing its PPE guidance on workers at the highest risk of exposure.
“That could include an unprotected splash in the face with raw cow milk or on the poultry setting, something that might have happened during a depopulation or culling event where the individual was not wearing appropriate PPE,” Shah said.
"There may be individuals who were infected ... but who do not recall having symptoms," Shah said. "That means that we in public health need to cast a wider net in terms of who is offered a test so that we can identify, treat and isolate those individuals."
“Simply put, the less room we give this virus to run, the fewer chances it has to cause harm or to change, and the best way to limit the virus’s room to run is to test, identify, treat and isolate as many cases as possible in humans and as quickly as possible,” Shah said.
CDC made the recommendations in conjunction with release of a serological survey in its weekly Morbidity and Mortality Report that found eight of 115 workers who were exposed to H5N1 bird flu during outbreaks among dairy cows at farms in Michigan and Colorado showed evidence of recent infection. All eight “reported milking cows or cleaning a milking parlor. Four workers remembered having symptoms, mostly conjunctivitis.”
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Only one of the workers reported working with infected cows even though they were working with cows on infections, Demetre Daskalakis, CDC’s director of the National Center for Immunization and Respiratory Diseases, said on the media call.
He added that “none wore respiratory protection and less than half wore eye protection, highlighting the need for better tools to support worker protection.”
An “important limitation” to the survey data, he added, “is that the interviews were conducted on an average 49 days after the first exposure to infected cows, with some workers interviewed up to 90 days after their first exposure. That makes recall of minor symptoms potentially difficult.”
There have been 46 human cases of H5 in the U.S. in 2024, CDC says – 25 due to the ongoing outbreak in dairy cows, which includes 21 in California. and 20 due to poultry depopulation, including 11 recent cases from Washington.
In the remaining case, in Missouri, there is “no known animal or animal product exposure,” Daskalakis said.
“Dairy farms with infected herds can reduce the risk of H5 avian influenza virus infections among workers by following CDC recommendations to protect workers such as using engineering controls, providing PPE, and providing worker education,” the MMWR said. “While the risk to the general public remains low, people who have been exposed to animals infected or potentially infected with avian influenza H5N1 viruses should watch for symptoms, even very mild symptoms like eye irritation, and seek care and get tested if they experience symptoms.”
Shah said the goal behind the “intensification” of CDC’s recommendations “is to actively identify exposed workers with H5 even if their symptoms are so mild as to be unnoticeable, so that those workers too can be offered treatment in isolation.”
“There is nothing that we've seen in the new serology data that gives rise to a concern about person-to-person transmission,” he said. Nevertheless, CDC is recommending Tamiflu even for asymptomatic workers “to drive down the levels of virus in their body, which … helps us keep that risk as low as possible.”
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