When SARS-CoV-2 first began rampaging around the world, it was thought to primarily affect the respiratory system. It soon became clear that the virus had more far-reaching effects, including on the gastrointestinal system and its bacterial symbionts.
One early study suggested that nearly 20 percent of patients with confirmed SARS-CoV-2 infection had gastrointestinal symptoms. That same study found that COVID-19–infected people shed viral RNA in their feces—another clue that the virus was getting into the gut.
Since then, researchers have identified patterns in the makeup of gut bacteria—a state called ‘dysbiosis’ in which there is loss of diversity and beneficial bacteria but an increase in bad bacteria—that are associated with poorer outcomes and slower recovery from COVID-19.