Unusual 2019-2020 flu season linked to more transmissible strain

The 2019-2020 flu season in the U.S. was unusual in a number of ways. Cases picked up in August rather than the more typical fall and early winter months, and it hit children particularly hard. It was also dominated early on by a Type B influenza virus instead of one of the much more common Type A viruses like H1N1 or H3N2.