Scientists Urge Better Surveillance as Bird Flu Spreads to US Cattle

A recent outbreak of the H5N1 bird flu virus in dairy cows across nine U.S. states has raised concerns among scientists and public health officials about the potential for the virus to mutate and spread to humans. While the virus has not been found in pasteurized milk, the slow response and insufficient data collection have hampered efforts to control the outbreak and assess its scale.

The H5N1 virus, commonly known as bird flu, typically infects birds but has now been detected in cattle. Researchers believe the virus may have jumped from an infected wild bird to a cow as early as November, but the outbreak was not identified until March. This delay suggests that current surveillance programs are inadequate, according to experts. "We are not doing enough," said Isabella Eckerle, head of the Geneva Centre for Emerging Viral Diseases in Switzerland. "The moment it does [transmit easily to humans], it will be an emergency."

The Centers for Disease Control and Prevention (CDC) and the United States Department of Agriculture (USDA) have been working to monitor and contain the outbreak. The CDC has launched a wastewater tracking dashboard to monitor the spread of the virus, while the USDA has mandated testing of lactating dairy cows before they are moved between states. Despite these efforts, researchers argue that more data and transparency are needed to understand the virus's distribution and evolution.

The USDA has detected H5N1 in 49 dairy herds, which represents about 1% of dairy farms in the affected states. However, the actual number of infected herds is likely higher, as testing has been limited. "There’s almost certainly been a lot more human cases than just the one," said Thomas Peacock, a virologist at Imperial College London. One human case has been confirmed in a dairy worker in Texas, who experienced only mild symptoms and has since recovered.

The CDC has emphasized that the overall risk to the public remains low, as human infections are rare and typically occur through direct contact with infected animals. "Right now, the H5N1 bird flu situation remains primarily an animal health issue," the CDC stated. However, the agency is taking "aggressive steps" to ensure farm worker safety and monitor potential human cases.

The USDA and the Food and Drug Administration (FDA) have assured the public that commercial milk and meat supplies are safe. Pasteurization and proper cooking temperatures effectively eliminate the virus. "Our milk is cleared to a high temperature for a brief period of time, inactivating H5N1," said Eric Deeble, deputy assistant secretary for the Office of Congressional Relations at the USDA.

Despite these reassurances, the outbreak has highlighted the need for improved surveillance and data collection. Researchers have called for more extensive testing of cattle and farm workers, as well as antibody studies to determine the extent of exposure. "This is something that should be done immediately," said Eckerle.

The outbreak has also underscored the importance of incentivizing farmers to report suspected cases and cooperate with testing efforts. The USDA has announced a plan to compensate farmers affected by H5N1 outbreaks, which could help increase testing and data collection.

The H5N1 virus has a history of causing concern among public health officials. Since its emergence in 1996, it has primarily affected birds but has occasionally infected humans, with a high mortality rate. Between 2003 and 2024, there have been 888 human cases of H5N1, with 463 resulting in death, according to the World Health Organization.

The current situation is reminiscent of past outbreaks, such as the 2009 H1N1 swine flu pandemic, which highlighted the importance of early detection and rapid response. The slow response to the current H5N1 outbreak in cattle has raised concerns about the potential for future pandemics. "The infrastructure we have in place is insufficient to prevent future pandemics," said Jonathan Pekar, an evolutionary biologist at the University of California, San Diego.

As the situation continues to evolve, public health officials and researchers are closely monitoring the virus for any signs of mutation that could increase its ability to spread among humans. "From a pandemic-potential perspective, to try and understand how bad this is and what’s going on, it’s frustrating," said Peacock.

In the meantime, the CDC and USDA are urging the public to stay informed and take precautions, particularly those who work with livestock. "We should be alert, not alarmed," said Dr. Nirav D. Shah, principal deputy director of the CDC.