The WHO announced on Friday that extremely high amounts of the H5N1 bird flu virus strain have been found in raw milk from sick animals. However, it is unknown how long the virus can remain in milk.
The first cases of avian influenza A(H5N1) were reported in 1996, but since 2020, the frequency of bird outbreaks and infected animal cases have increased dramatically.
Tens of millions of chickens have died as a result of the strain, which has also infected wild birds and land and marine mammals.
Experts were surprised to see cows and goats added to the list last month, as they were not previously believed to be vulnerable to this particular strain of influenza.
US authorities earlier this month said a person working on a dairy farm in Texas was recovering from bird flu after being exposed to cattle.
“The case in Texas is the first case of a human infected by avian influenza by a cow,” said Wenqing Zhang, head of the global influenza programme at the World Health Organization.
“Bird-to-cow, cow-to-cow and cow-to-bird transmission have also been registered during these current outbreaks, which suggest that the virus may have found other routes of transition than we previously understood,” she told a media briefing in Geneva.
It was only the second case of a human testing positive for bird flu in the United States, and came after the virus sickened herds that were apparently exposed to wild birds.
“Now we see multiple herds of cows affected in an increasing number of US states, which shows a further step of the virus spillover to mammals,” Zhang said.
“The virus has also been detected in milk from infected animals.”
Although specialists were still determining the precise duration of the virus’s survival in milk, Zhang said that there was a “very high virus concentration in raw milk”.
The Texas health department has stated that since dairies are obligated to discard milk from sick cows, the cattle infections do not pose a threat to the commercial milk supply. Pasteurization eliminates the virus as well.
“It is important for people to ensure safe food practices, including consuming only pasteurised milk and milk products,” said Zhang.
