As the avian influenza virus continues to spread among cows in the U.S., the country's health agencies are intensifying monitoring efforts and developing vaccines as needed to prepare for a potential outbreak in humans.
An American farm's dairy cows. Image Source: Shutterstock / Roman Melnyk
Vivien Dugan from the Centers for Disease Control and Prevention (CDC) stated at a health officials' meeting on April 25th, "Currently, the risk of avian flu remains low, but with new data emerging, we are still in a strong state of readiness."
The immediate priority is tracking the spread of the virus. So far, the U.S. Department of Agriculture has confirmed the presence of the H5N1 avian flu virus in dairy cows from 33 farms in 8 states and in 6 cats from 3 states.
Rosemary Sifford from the USDA mentioned at the meeting that genetic sequencing revealed only one mutation in a sample taken from 260 infected dairy cows, indicating that H5N1 has adapted to infect mammals. However, this marker has been found in other infected mammals before and does not affect the virus's ability to spread among mammals. Additionally, no similar mutations were found in 10 other samples collected from the same group.
"It remains predominantly an avian flu virus with no significant changes... in other words, it has not become a cow virus," Sifford said.
According to data presented at the meeting, CDC has tested 23 individuals closely in contact with these animals for the virus. Only one person tested positive, a dairy farm worker from Texas, with the sole symptom of red eyes. Dugan mentioned that to enhance testing capabilities, CDC recently increased funding for genetic sequencing centers in 6 states.
Another crucial measure being taken is ensuring the safety of the U.S. milk supply. Milk from infected cows contains a high amount of the virus. Preliminary tests by the Food and Drug Administration (FDA) found genetic traces of avian flu in 1/5 of milk samples.
"It's important to note that this does not mean the samples contain the complete infectious virus," said Donald Prater from the FDA, explaining that their testing method can detect any genetic material, including remnants of dead viruses.
The majority of milk sold in the U.S. undergoes pasteurization, a process that kills pathogens with heat. Prater mentioned that the effectiveness of pasteurization against the H5N1 virus has not been specifically studied, but research on similar flu viruses suggests it is effective. This is why people should avoid consuming or coming into contact with raw dairy products.
Two candidate vaccines for H5N1 are also in development. Dugan stated that preliminary tests by the CDC show these vaccines are effective against the current strain in cows in laboratory tests.
David Boucher from the Assistant Secretary for Preparedness and Response (ASPR) mentioned at the meeting that ASPR is stockpiling materials for avian flu vaccines. ASPR and its commercial partners have produced hundreds of thousands of doses of H5N1 vaccines that can be rapidly distributed for clinical trials or emergency use if needed.
"Based on the current risk assessment by the CDC, vaccination is not currently necessary. However, if the situation changes, we want to be prepared," Boucher said, noting that the stored materials are sufficient to produce an additional 10 million doses of vaccine. ASPR has also contracted with vaccine manufacturers to further increase production if necessary.
