WASHINGTON (AP) — Health authorities say a man in Mexico died from a type of bird flu called H5N2 that has never before been found in a human.

The World Health Organization says Mexican health officials confirmed the April death but don’t know how the man became infected.

The strain that killed the man is not the same type of bird flu that is circulating in U.S. dairy cow populations and has mildly infected three farmworkers.

There are many types of bird flu and some have killed people in various parts of the world, usually after contact with sick birds.