The US is entering a riskier season for spread of H5N1 bird flu. Here’s why experts are worried

With the approach of fall and cooler weather across the United States, officials say the risk posed by the H5N1 bird flu virus could rise — and they’re taking steps to prevent the creation of a hybrid flu virus that could more easily infect humans.

With the approach of fall and cooler weather across the United States, officials say the risk posed by the H5N1 bird flu virus could rise — and they’re taking steps to prevent the creation of a hybrid flu virus that could more easily infect humans. Fall and winter months present more opportunities for H5N1 to spread and change since both cows and other flu viruses will be on the move. While most human infections in the current outbreak have been mild and self-limiting, each new host gives the virus a chance to get better at infecting people. “To be clear, we have no evidence so far that this virus can easily infect human beings or that it can spread between human beings easily in a sustained fashion,” said Dr. Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health. “If it did have those abilities, we would be in a pandemic. “The second we know that someone gave it to someone else relatively easily, that’s a new pandemic, and it will be around the globe, probably in a matter of weeks,” Nuzzo said at a seminar hosted by the Health Coverage Fellowship. The concern comes as scientists are urgently trying to solve the mystery of how a person in Missouri who had no contact with animals became infected by a type of bird flu. Few details have been released. The person had “significant underlying health conditions” that probably made them more susceptible to the infection, Dr. Nirav Shah, principal deputy director of the US Centers for Disease Control and Prevention, said Thursday.