What makes the H1N1 pandemic tick?

• Position: YOUR LIFE

As the number of deaths related to the pandemic H1N1 virus, commonly known as "swine flu," continues to rise, researchers have been scrambling to decipher its inner workings and explain why the incidence is lower than expected in older adults. In one study, a researcher from the University of Texas Southwestern Medical Center, Dallas, and his collaborators in California show that the molecular makeup of the current H1N1 flu strain is strikingly different from previous H1N1 strains as wail as the normal seasonal flu, especially in structural parts of the virus that normally are recognized by the immune system.

Prior research has shown that an individual's immune system is triggered to tight off pathogens such as influenza when specific components of the immune system--namely antibodies, B-cells, and T cells--recognize the parts of a virus known as epitopes. An individual's ability to recognize those epitopes--spurred by past infections or vaccinations--helps prevent future infections. The challenge is that these epitopes vary among flu strains.

"We hypothesize that older people are somewhat protected because the epitopes present in flu strains before 1957 may be similar to those found in the current H1N1 strain, or at least similar enough that the immune system of the previously infected person recognizes the pathogen and knows to attack," surmises Richard Scheuermann...