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Prior exposure to pandemic influenza viruses weakens severity.
Reuters 11/21/2011 18:21 Updated: 21/11/2011 19:35
The immunity obtained with version prior seasonal influenza virus reduced the severity of the pandemic of 2009, according to a U.S. study.
A team of Texas studied hundreds of adults during the influenza season of 2009-2010 and found that those who already had the seasonal flu were less likely to become infected with the pandemic strain or become seriously ill if they catch the virus population never been exposed to previous influenza virus.
The immune system remembers past encounters with certain viruses and that allows you to remove them in the future. In the 2009 pandemic, influenza virus belonged to the same family of virus strains, known as H1N1, seasonal flu earlier years.
"Both are called H1 for something. They are related. The H1 pandemic is different from seasonal, but still a H1" said Mark Lipsitch, a professor at the School of Public Health at Harvard who was not part of the study.
H1 is a type of protein produced by influenza virus. When the immune system is exposed to the virus, the body makes molecules called antibodies that recognize and block the protein so the virus can not invade cells.
When the pandemic began to grow in the U.S. in fall 2009, the authors began to follow to 513 adults on the campus of Texas A & M University.
When the study began in September, the team drew blood samples from them and if they got sick, I drew a new blood sample and underwent a throat swab.
During the season, 116 were infected with the pandemic virus, as determined by antibodies in blood at the end of the study in the spring of 2010.
33 percent of those without signs of blood antibodies against the virus of the influenza season prior to the start of the study were infected with the pandemic strain. The same occurred with only 18 percent of people with antibodies.
Dr. Robert Couch, author of the study and professor at Baylor College of Medicine, said that the results show that a "dose" after the seasonal H1N1 virus provided some protection against the pandemic virus.
"The immunity did not prevent influenza. We had a flu epidemic, but not the disaster that was anticipated," Couch told Reuters Health.
Compared with 1918 pandemic that killed some 675,000 Americans, for example, 2009 was "mild", with at least 14,000 deaths, a figure lower than that registered with the seasonal flu.