The body’s response to influenza infection creates a potentially deadly catch-22 situation, recent research has found.

When influenza strikes, the body begins to produce a large amount of glucocorticoids (GC), researchers at the Yale University School of Medicine discovered using mouse models. GCs are usually produced in response to stress, but they also help the body to reduce inflammation—an important part of surviving a flu infection. Unfortunately, the GCs also suppress the immune system, leaving the body open to secondary bacterial infections, according to the study.

Other recent studies have shown it is usually these secondary bacterial infections that cause flu-related deaths. (McKnight’s, 1/26/10) Although mice in this study with no GCs were better able to fight off the secondary bacterial infection, they experienced lethal levels of inflammation from the influenza virus. The report appears in the Feb. 18 issue of the journal Cell Host and Microbe.