In 1957, an Asian flu pandemic infected about 45 million Americans and killed 70,000. Eleven years later, from 1968 to 1969, the Hong Kong flu pandemic infected 50 million Americans and caused 33,000 deaths. It also cost about $3.9 billion. In 1976, about 500 soldiers became infected with swine flu over a few weeks. However, by the end of the month, investigators found that the virus had "mysteriously disappeared", and there were no more signs of swine flu anywhere on the post. There were a small number of isolated (far-apart) cases around the U.S. However, these were in people who were thought to have caught the virus from pigs.