Some survivors of COVID-19 carry worrying signs that their immune system has turned on the body, reminiscent of potentially debilitating diseases like lupus and rheumatoid arthritis, a new study has found.

At some point, the body’s defense system in these patients shifted into attacking itself, rather than the virus, the study suggests. The patients are producing molecules called "autoantibodies” that target genetic material from human cells, instead of from the virus.

This misguided immune response may exacerbate severe COVID-19. It may also explain why so-called "long haulers” have lingering problems months after their initial illness has resolved and the virus is gone from their bodies.