The 1968 pandemic, also known as the Hong Kong flu, was caused by an influenza A (H3N2) virus that was first noted in the U.S. in September. The estimated number of deaths was 1 million worldwide and about 100,000 in the U.S.

Most excess deaths were in people 65 years and older. The H3N2 virus continues to circulate worldwide as a seasonal influenza A virus and is the most dangerous influenza A virus in humans.