Bird flu outbreak raises pandemic concerns as virus spreads across US farms

Health experts warn that the simultaneous circulation of bird flu and seasonal influenza could increase the risk of a new virus capable of spreading between humans. A growing bird flu outbreak across the United States is raising concerns among public health experts, as infections spread through dairy cattle and poultry flocks and scientists warn about the potential for the virus to evolve. The H5N1 virus is being blamed for at least one human death in Washington state, where the outbreak has been particularly severe. But health officials may not know the full extent of human infections. The United Farm Workers union warns that increased immigration enforcement could discourage agricultural workers from reporting possible infections or seeking assistance from public health agencies. "Given the current and ongoing ICE surge ... many or most of the workers are understandably reluctant to proactively engage with public agencies," the union said in a social media post. RELATED STORY | Bird flu detected in California elephant seals for first time According to data from the Centers for Disease Control and Prevention, H5N1 infections have been confirmed in dairy cattle herds in six states over the past 30 days. The virus has also been detected in backyard and commercial poultry flocks across 17 states during that period. While the outbreak has raised concerns about human exposure, particularly among people who work closely with infected animals, there is currently no evidence of sustained human-to-human transmission of H5N1. However, scientists warn that could change. Dr. Jennifer Nuzzo, director of Brown University's Pandemic Center, says scientists have been concerned about H5N1 for decades. "This H5N1 virus has been the top of our future pandemic worry list for a really long time, for 25 years," Nuzzo said. One of the biggest concerns is the overlap between the ongoing bird flu outbreak and the start of the traditional influenza season. As seasonal flu infections increase, scientists worry about the possibility of avian and human influenza viruses infecting the same host and exchanging genetic material. "When you have a whole lot of bird virus circulating, at the same time that you have a whole lot of human virus circulating, it just raises worries that those two viruses are gonna find each other and swap genes," Nuzzo explained. That process, known as genetic reassortment, could potentially produce a new influenza virus with characteristics that make it more dangerous to humans. Nuzzo says the worst-case scenario would be the emergence of a virus that people have little or no immunity against and that can spread easily from person to person. RELATED STORY | Pet owners urged to watch for screwworm as cases emerge in dogs For now, H5N1 remains primarily an animal health threat, with human infections generally associated with exposure to infected animals. But the continued spread of the virus among dairy cattle and poultry creates additional opportunities for human exposure and viral evolution. Scientists are closely monitoring those developments, particularly as seasonal influenza begins circulating more widely.