In recent years, H5N1 has spread widely among wild birds, poultry, land and marine mammals and now among dairy cattle.
The UN health agency, World Health organisation (WHO), says the H5NI avian influenza virus has so far shown no signs of adapting to allow human-to-human transmission.
So far, one human case has been reported in the United States since the outbreak of bird flu among the millions of dairy cattle across the country.
At least 220 people are monitored and at least 30 have been tested.
"However, many more people have been exposed to infected animals, and it is important that all those exposed are tested or monitored and receive care if needed," Tedros Ghebreyesus, Director-General of WHO, said at a news conference on Wednesday.
"So far, the virus does not show signs of having adapted to spread among humans, but more surveillance is needed," he urged.
The WHO chief also said that though the virus has been detected in raw milk in the US, "preliminary tests show that pasteurisation kills the virus".
"WHO's standing advice in all countries is that people should consume pasteurised milk," he highlighted.
Pasteurisation is a heat treatment process for milk that reduces the numbers of possible pathogenic microorganisms to levels at which they do not represent a significant health hazard. It also extends the usable life of milk.
Mr Ghebreyesus also noted that based on available information, WHO continues to assess the public health risk posed by H5N1 avian influenza to be low and low-to-moderate for people exposed to infected animals.
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He added that the agency has a system for monitoring influenza globally through a network of centres in 130 countries, seven collaborating centres and 12 reference laboratories with the capacities and biosafety requirements to deal with H5 viruses.
"We also have the Pandemic Influenza Preparedness Framework to support the rapid development and equitable distribution of vaccines in case of an influenza pandemic," he said.
In recent years, H5N1 has spread widely among wild birds, poultry, land and marine mammals and now among dairy cattle.
Since 2021, there have been 28 reported cases in humans, although no human-to-human transmission has been documented.
The outbreak in the United States has so far infected 36 dairy herds in nine states.
