10. Knighted Penguin
Isolated in northern China, this virus was similar to the virus that spread before 1957. For this reason, individuals born before 1957 were generally protected, however children and young adults born after that year were not because they had no prior immunity. By January 1978, the virus had spread around the world, including the United States. Because illness occurred primarily in children, this event was not considered a true pandemic. Vaccine containing this virus was not produced in time for the 1977-78 season, but the virus was included in the 1978-79 vaccine.