Why flu is deadly among the elderly

There’s good reason behind doctors’ recommendation that older adults receive the flu vaccine annually. Each year, 90 percent of deaths worldwide related to influenza A virus (IAV) strike men and women aged 65 and older. The trouble, according to a widely accepted theory, is that IAV replicates quickly and overwhelms older adults’ immune systems, thus making them more susceptible to catching pneumonia and the like.

A study published in April in the journal Science suggests that the body’s inflammatory immune response, not the virus, leads to death. Akiko Iwasaki, Ph.D., Waldemar Von Zedtwitz Professor of Immunobiology and an investigator of the Howard Hughes Medical Institute, and colleagues found that immune cells from older adults secrete significantly less interferon, a key antiviral protein.

The authors then created mice with immune systems that mimicked this weakened response. “Although the virus was not sufficient to kill mice, the immune response, driven by neutrophils [white blood cells], led to excessive inflammation and lung damage,” says lead author Padmini S. Pillai, a doctoral student in Iwasaki’s lab.

The study could point to new anti-inflammation flu treatments that target and calm this overactive immune response.

Read “Innate virus recognition and autophagy” and watch accompanying video here.