People born before 1957 appear to have some immunity to the H1N1 virus, the New York Times reports. Tests show that older adults have antibodies that attack the virus, probably because they've been exposed to a similar virus. Experts believe the swine flue virus, like seasonal influenzas before 1957, is related to the virus that caused the 1918 pandemic, and is not linked to the viruses that replaced it after the 1957 Asian flu pandemic.
Only 13% of the 247 people hospitalized with the new virus have been over 50, and most of those suffered from other medical conditions. The pattern holds true in the "ground zero" nation where the strain was first identified. "I saw young adults on respirators and young adults dying," said an expert who recently visited Mexico City. "Older adults weren't really part of the pattern."