This time of year, doctors often recommend flu shots for people who are young, old, pregnant or immunocompromised. Michelle Goody suggests adding people with muscular dystrophy to the list.

After the University of Maine research assistant professor injected the flu virus into the bloodstreams of zebrafish with Duchenne muscular dystrophy (DMD), damage to their muscles was greatly exacerbated.

DMD is the most common type of muscular dystrophy and is characterized by progressive muscle degeneration and weakness. The genetic disease is caused by the absence of dystrophin, a protein that helps muscle cells remain intact. People with DMD — almost all males — have difficulty standing up and walking, and may have heart and lung problems.

Goody first injected human Influenza A virus (IAV) into the bloodstream of 2-day-old healthy zebrafish. Within 24 hours, they exhibited symptoms of an influenza infection — their hearts were swollen, their mobility was reduced and they were shaking.

The data, says Goody, indicate IAV can enter and infect live zebrafish muscle cells, and that “muscle degeneration, pain and weakness may be, at least in part, due to direct infection of muscle xcells by IAV.”

Muscle complications with viral infections also could be due to collateral damage by an activated immune system, she says.

Goody, the first person to discover that the flu virus can enter and infect muscle cells in a live animal, then injected the same dose of the flu virus into the bloodstream of zebrafish with muscular dystrophy.

These zebrafish soon displayed severe muscle damage. This suggests “that muscle damage caused by Dystrophin-deficiency and IAV infection is synergistic,” wrote Goody in PLOS Currents: Muscular Dystrophy.