New Treatment Clues for Fatal Combination of Flu and Bacterial Infection

It is known that being sick with influenza virus increases the susceptibility to bacterial infection which can have very serious implications, and it is actually the secondary infection that is the main cause of death for several hundred thousand people each year. Scientists from the Max F. Perutz Laboratories (MFPL) of the Medical University of Vienna gained new insights into how much harm bacteria can cause to the lung of people having the flu, with possible options for better treatment.

An infection with both the flu and bacteria is often a fatal combination, and the researchers hope that their results could prompt the development of alternative treatments for flu-related bacterial infections, to improve patient outcome and prevent permanent lung damage.

According to the World Health Organization (WHO), around five to 15 percent of the population are affected by upper respiratory tract infections during seasonal flu outbreaks, and between 250 000-500 000 people die of the illness every year. However, a main cause of death in people having the flu is actually a secondary infection with bacteria.

One type of bacteria that the immune system usually prevents from spreading and becoming harmful for us is called Legionella pneumophila. However in some circumstances, such as when we're infected with influenza virus, Legionella can cause pneumonia, an inflammatory disease of the lung that if left untreated can leave the lung permanently damaged and even cause death. "In our model system an infection with influenza and Legionella was fatal. We expected that this would be caused by the bacteria growing and spreading like crazy, but what we actually found was that the number of bacteria didn't change, which was a big surprise," says Amanda Jamieson, the lead author of the report.

Amanda Jamieson and her collaborators could show now that the damage to the lung tissue caused by a co-infection with flu and Legionella is not properly repaired, as the influenza virus suppresses the body's ability to repair tissue damage. In case of an additional Legionella infection this may lead to fatal pneumonia. However, treatment with drugs that activate tissue repair pathways significantly improved the outcome. This suggests that new treatment options to deal with co-infections of flu and bacteria should be explored. Amanda Jamieson, who will take up an Assistant Professorship at Brown University, USA, in two months, says: "My group will continue to work on tissue repair models and explore different avenues for the treatment of flu/bacterial co-infections.