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By John Lauerman
May 7 (Bloomberg) -- Swine flu evolved from human viruses circulating in pigs for more than a decade, a finding that may explain why people in their 30s and 40s are getting sicker than the elderly in the U.S. and Mexico, scientists said today.
Older people may have some immunity against swine flu because of exposure to similar viruses as long as 70 years ago, before the virus?s ancestors switched to infecting pigs, said Robert Belshe, a St. Louis University influenza expert, who wrote a commentary on studies published in the New England Journal of Medicine.
The percentage of people aged 30 to 44 who are hospitalized from swine flu is higher than in seasonal flu, according to U.S. Centers for Disease Control and Prevention. That suggests younger adults may have less immune protection against swine flu than older people, Belshe said.
?They may have been infected with similar viruses in the 1930s and 1940s,? Belshe said today in a telephone interview. ?Their exposure to seasonal viruses may be giving them some protection.?
Editors: Kurt Heine, Reg Gale
May 7 (Bloomberg) -- Swine flu evolved from human viruses circulating in pigs for more than a decade, a finding that may explain why people in their 30s and 40s are getting sicker than the elderly in the U.S. and Mexico, scientists said today.
Older people may have some immunity against swine flu because of exposure to similar viruses as long as 70 years ago, before the virus?s ancestors switched to infecting pigs, said Robert Belshe, a St. Louis University influenza expert, who wrote a commentary on studies published in the New England Journal of Medicine.
The percentage of people aged 30 to 44 who are hospitalized from swine flu is higher than in seasonal flu, according to U.S. Centers for Disease Control and Prevention. That suggests younger adults may have less immune protection against swine flu than older people, Belshe said.
?They may have been infected with similar viruses in the 1930s and 1940s,? Belshe said today in a telephone interview. ?Their exposure to seasonal viruses may be giving them some protection.?
Editors: Kurt Heine, Reg Gale
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