Long covid is not the only chronic condition triggered by infection

SOME INFECTIONS—HIV/AIDS, for example—are chronic. If you catch one you are stuck with it indefinitely, unless a treatment exists to clear away the guilty pathogen. Many, though, are acute. Unless they kill you, your immune system will do the clearing and you can carry on as before.

For an unlucky few, however, that is not the end of the story. Certain infections have a second act, brought about by some consequence of the pathogen’s visit. Sometimes, the physiological chain is clear. One well-known example concerns a variant of Streptococcus that causes rheumatic heart disease when the body’s immune response also attacks cardiac tissue. Often, though, the connections are more opaque—particularly with neurological symptoms. Indeed, it may not even be clear which pathogen is involved.