In the wake of a recent outbreak of avian influenza detected in dairy cows and goats in the United States, the World Health Organization is calling on governments to increase their surveillance and to “remain vigilant” regarding the possible spread of this deadly disease to their countries.
Dr. Wenqing Zhang, head of the WHO’s global influenza program, said Friday that investigations are underway to determine the extent and severity of the H5N1 bird flu found in 29 herds in eight U.S. states since March.
“While WHO and its partners are closely monitoring, reviewing, assessing and updating the risk associated with H5N1 and other avian influenza viruses, we call on countries to remain vigilant, rapidly report human infections if any, rapidly share sequences and other data, and reinforce biosecurity measures on animal farms,” said Zhang.
Zhang also told journalists in Geneva that on April 1 a laboratory-confirmed case of avian influenza was found in a man who was working at a dairy cattle farm in Texas.
“The case in Texas is the first case of a human infected by avian influenza by a cow,” she said, noting that he most likely got infected “through the direct contact with cows.”
“Now we see multiple herds of cows affected in an increasing number of U.S. states, which shows a further step of the virus spillover to mammals,” she added, warning that “farm workers and others in close contact with cows should take precautions in case the animals are infected.”
Zhang also noted that so far there has been no detected transmission of the virus from cattle to other mammals, though bird-to-cow, cow-to-cow and cow-to-bird transmission have occurred during the current outbreaks.
“Although a lot is still under investigation, this suggests that the virus may have found ... routes of transmission other than what we previously understood,” she said. “While this sounds concerning, it is also a testament to strong disease surveillance which allows us to detect the virus.”
Avian influenza A(H5N1) first emerged in 1996. In 2020, the virus spread into Africa, Asia, and Europe and then in 2022, it crossed into North and South America.
“In recent years, we see the virus spillover to mammals,” Zhang said, noting that the U.S. Department of Agriculture has detected infections in “around 200 mammals.”
Human infections of avian flu are rare and tied to exposure to infected animals and environments. The WHO reports nearly 900 cases have been detected since 2003. About half of those infected with the disease reportedly have died.
In the early years, most cases were found in Asia and Southeast Asia. WHO reports the relatively few U.S. and European cases reported to the agency over the past two years have been mild.
Zhang said the virus in dairy cows currently circulating in the United States also has been detected in milk from infected animals.
“We also received reports that there is very high virus concentration in raw milks. But exactly how long the virus will be able to survive in the milks remains under investigation.
“So, we recommend that people really should consume pasteurized milk and milk products,” she said, adding that this recommendation applies to people “in the whole world.”
Nearly 20 vaccines are currently licensed for pandemic use for influenza. Zhang said two “candidate vaccine viruses” are available that can respond to bird flu outbreaks in dairy cows and other animals in the United States.
“Having candidate vaccine viruses really allows us to be prepared to quickly produce vaccines for humans, if this becomes necessary,” she said, adding that at least four antiviral medications, including oseltamivir, widely marketed as Tamiflu, are available to treat people who may become sick with bird flu.
