One of the most baffling features of the swine flu outbreak is that, unlike seasonal influenza, severe disease largely does not occur in the elderly. The U.S. Centers for Disease Control and Prevention (CDC) plans to release a detailed report that says some older people have antibodies that react to the novel H1N1 virus behind the swine flu outbreak.
CDC’s influenza chief, Nancy Cox, discussed this in an interview posted on ScienceInsider last week, but CDC’s Morbidity and Mortality Weekly Report later today or tomorrow will have a detailed account of the findings.
One reason why the elderly may have antibodies is from exposure to an older cousin of the swine flu strain. At a press conference today, CDC epidemiologist Daniel Jernigan noted that between the pandemics of 1918 and 1957, an H1N1 circulated in the United States that appears to have left some people with an antibody response that in test-tube studies “cross-reacts” with the new H1N1 virus. “That is not something that tells you about protection,” cautioned Jernigan. “We can infer from that to some degree that there is some level of protection, but we don’t have a good answer to that right now.”