In the United States, as the avian influenza virus continues to spread among dairy cows, health authorities are intensifying monitoring measures and have stated that they will develop vaccines when necessary to prepare for a potential human epidemic. A spokesperson for the Centers for Disease Control and Prevention mentioned at a recent meeting that although the risk of avian influenza infection in humans remains low, vigilance in prevention and control must be maintained as the situation evolves and new data is collected.
The primary task is to track the spread of the virus. So far, officials have confirmed that dairy cows on 33 farms across 8 states and some pet cats in 3 states are infected with the H5N1 virus. According to one expert, when gene sequencing was performed on samples from 260 infected dairy cows, only a small portion of the samples showed mutations, indicating that the H5N1 virus can effectively infect mammals. Moreover, this type of mutation has been found in other infected mammals in the past but did not change their ability to transmit the virus among themselves. In short, the virus has not adapted to become one that specifically targets dairy cows.
The CDC has also tested 23 people who had close contact with the infected animals, with only one person testing positive, showing only minor symptoms of red eyes. Another key measure is to ensure the safety of America’s milk supply. Although traces of avian influenza virus genes were found in some milk samples after initial testing, it is important to note that this does not mean that the samples contain a complete virus capable of causing infection. Most milk sold in the United States has been pasteurized and although the effectiveness of pasteurization against the H5N1 virus has not yet been evaluated, studies on other similar influenza viruses suggest that pasteurization is effective.
Currently, two candidate vaccines against the H5N1 virus are under development. Preliminary tests show that both vaccines are effective against the current virus strains infecting dairy cows. An official in the United States stated that emergency agencies and commercial partners have stockpiled several hundred thousand doses of H5N1 vaccine that can be used quickly for clinical trials or emergency use if necessary. In addition, enough materials have been stockpiled to produce an additional 10 million doses of vaccine, and contracts have been signed with vaccine manufacturers to quickly increase production if necessary.
