Scientists are sounding alarms about a genetic mutation that was recently identified in four dairy cow herds, nearly one year after H5N1 bird flu was first reported in Texas dairy cattle.

Prior exposures to specific types of seasonal influenza viruses promote cross-reactive immunity against the H5N1 avian influenza virus, according to new research from the Perelman School of Medicine at the University of Pennsylvania.

Older adults who were exposed to seasonal flu viruses that circulated prior to 1968 are more likely to have some protection against H5N1, and children would benefit more from H5N1 vaccines.