New data on hospitalizations and deaths caused by the pandemic H1N1 influenza virus show that it is "a disease of the young," said Dr. Anne Schuchat of the federal Centers for Disease Control and Prevention on Tuesday.
From Sept. 1 to Oct. 10, there were 4,958 hospitalizations from laboratory-confirmed swine flu in the 27 states reporting to the CDC, said Schuchat, who is director of the agency's National Center for Immunization and Respiratory Diseases. More than half of those cases, 53%, involved people younger than 25; 39% were ages 26 to 64, and only 7% were 65 and older. In contrast, with seasonal flu, 60% of hospitalizations involve patients 65 and older.
The disparity is even higher for fatalities. During the same time period, there were 292 deaths from swine flu in the 28 states reporting. In that group, 23.6% of those who died were younger than 25, 65% were 25 to 64, and only 11.6% were 65 and older. "That is dramatically different from seasonal flu, in which 90% of the fatalities occur in those over 65," Schuchat said at a morning news conference.
The difference, most researchers now suspect, is caused by the fact that senior citizens have been exposed to a swine-related virus in the past and that has produced some residual immunity, so they are less likely to be infected and are not as severely affected when they do contract it. Younger people have no such immunity.