By Shelly Hwang
February 17, 2010
It’s flu season, and with the H1N1 virus being the spotlight of current news and the CDC pushing for nation-wide flu vaccination, people have become terrified of the influenza virus. However, a recent study done by researchers at the Yale University School of Medicine (published in the February 18 issue of Cell Host and Microbe) revealed that the stress response caused by the flu actually protects against death by secondary infection by using mice with bacterial infections.
Influenza can damage the lungs but usually does not kill. However, secondary infections such as pneumonia can occur after infection with the influenza virus and are much more deadly. Each year, more than 200,000 U.S. residents are hospitalized for flu-related complications, and about 36,000 Americans die on average per year from complications of the flu (CDC Statistics).
While previous studies on the flu have shown repressing of the immune system, such studies have only studied a single pathogen and focused on local effects of influenza at the site of infection. In reality, organisms are exposed to multiple infectious agents at a time and the effect of influenza on the whole immune system has not been studied.
This study, led by Dr. Rusian Medzhitov from the Department of Immunology, used a mouse model to examine the effects of the lung infection caused by influenza on the immune response to bacterial infection. Surprisingly, the researchers found that the influenza lung infection led to increased production of glucocorticoids (GC), which are produced in response to stress and known to play a key role in regulating inflammation. They found that virus-induced GC production is essential to controlling inflammation, as shown by the death of mice lacking GC’s that were infected by multiple pathogens.
So the next time you find yourself miserable and overwhelmed with the unpleasant flu FACTS symptoms (Fever, Aches, Chills, Tiredness, Sudden symptoms), remember to thank the virus for protecting you from fatal secondary infections.