A recent study conducted at Penn State sheds some much-needed light on the origins of the flu virus that kills 36,000 Americans each year. The study concluded that the virus comes from a “viral reservoir” somewhere in the tropics.

“We now know where the influenza A virus comes from every year,” said Edward Holmes, professor of biology at Penn State. “And because we now know how the virus evolves, we have a much better chance of controlling it.”

The Penn State team found that the influenza A virus is frequently exchanging genes by “reassortment”, when multiple human influenza viruses infect a single person and shuffle their genes. This shuffling can sometimes allow the vaccine to acquire a new haemagglutinin, a protein that facilitates the entry of viral particles into the host cells. According to Holmes, these new haemagglutinins sometimes cause the vaccines to fail.

“We now know the strains are dying out each year in the northern and southern hemispheres. That tells us that they’re surviving somewhere else, and we believe it is a reservoir in the tropics,” said Holmes. “This tells us that to really understand how the influenza virus evolves on a seasonal basis, and to make the best vaccine, we need to focus our surveillance on the source population in the tropics, especially in places such as Southeast Asia.“

Source: Penn State