Swine Flu Had Lower Risk Of Serious Complications
According to U.S. research presented Tuesday, infection from the 2009 swine flu pandemic presented a lower risk of serious complications than other recent strains of the flu.
Researchers at Wisconsin’s Marshfield Clinic Research Foundation said that an analysis of influenza cases in the Midwestern U.S. state of Wisconsin showed infected individuals were younger than in earlier strains, but complications were not as likely as the H3N1 virus that arose in the 2007-2008 flu season.
"The pandemic 2009 influenza A(H1N1) virus caused widespread transmission in the United States and other countries," lead author Edward Belongia and colleagues wrote in the September 8 issue of the Journal of the American Medical Association (JAMA).
The study said that the Centers for Disease Control and Prevention (CDC) estimated the U.S. saw 43 million to 89 million infections during April 2009 to April 2010, "with mid-range estimates of 274,000 H1N1-related hospitalizations and 12,470 deaths," including seasonal and pandemic strains.
Researchers compared the characteristics of pandemic and seasonal influenza infections occurring in that defined population during its localized study in the state. The study used 6,875 patients in three flu seasons starting in 2007.
The team identified 545 H1N1 influenza cases in 2009, and 221 cases of the seasonal H1N1 flu, and 632 patients suffered the H3N2 infection from the 2007-2008 season.
The study said that children were not associated with more hospital admission or pneumonia cases when compared with seasonal H1N1 or H3N2.
Six out of 395 children with the 2009 H1N1 virus were admitted to the hospital, compared to five of 135 with seasonal H1N1 and eight of 255 with the H3N2 virus.
Six out of 150 adults with 2009 H1N1 of 4.0 percent were hospitalized, compared to 17 out of 377 cases of H3N2.
"Our results suggest that the clinical manifestations and risk of hospital admission are similar for 2009 H1N1 and other seasonal influenza A strains," the study’s authors wrote.
"The perceived severity of symptoms and risk of serious outcomes (pneumonia or hospital admission) were not increased," they added.
The World Health Organization declared the swine flu pandemic officially over last month.
According to the WHO, the virus strain killed over 18,449 people and affected about 214 countries and territories since it was discovered in Mexico and the U.S. in April 2009. Â
The swine flu virus spread swiftly around the world despite dramatic efforts to shut down Mexico, prompting U.N. health officials to declare a pandemic on June 11, 2009.
(JAMA. 2010;304[10]:1091-1098)
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