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.

Avian flu is not just for the birds; cases have been reported in the United States in dairy cows, as well as types of cats, a fox, a seal, and most recently, rats and domestic indoor cats, according to the latest data from the US Department of Agriculture (USDA)’s Animal and Plant Health Inspection Service (APHIS).