Long COVID, ‘Long Cold’: What to Know About Post-Acute Infection Syndromes

Post-acute infection syndrome encompasses chronic illnesses that occur after an infection from a virus, bacteria, or parasite. For example, this could include prolonged symptoms after COVID, caused by the SARS-CoV-2 virus; other infections caused by viruses, bacteria, or parasites; or Lyme disease, which is caused by certain types of bacteria.

“The prevalence of these post-acute infection syndromes differs between pathogens. For COVID, it’s estimated to be about 10% of the people who develop Long COVID. With seasonal influenza, the number is likely lower,” Iwasaki says. “We don’t know the exact percentages of people who suffer long-term consequences from different infections, but it can certainly happen after different viral infections, and also with bacterial infections like Lyme disease.”

Sometimes, it’s not fully known what pathogen, if any, leads to certain chronic diseases. ME/CFS is a long-term illness characterized by severe fatigue, sleep problems, and other symptoms worsened by physical activity. Scientists believe there may be many causes of ME/CFS, including various viral infections.

Plus, Long COVID and other post-acute infection syndromes can evolve into ME/CFS. “ME/CFS is a disease that lasts at least six months or longer, whereas Long COVID, generally, is defined as four to six weeks of prolonged illness after a presumed COVID infection,” Iwasaki says. “The timeline is different, but many people who developed Long COVID are now also developing ME/CFS—an estimated 50% from the first wave of COVID.”

It’s not that everyone who has Long COVID has ME/CFS, but one could turn into the other, she adds. “That’s a possibility that researchers are paying attention to, because there’s a commonality between these two diseases,” she says.

While different pathogens may trigger Long COVID, ME/CFS, and other post-acute infection syndromes, many of the chronic conditions share similar symptoms, such as fatigue, disrupted sleep, and pain.