My partner spent most of last week sick on the couch, tired and coughing. It seemed like a textbook case of COVID-19—but when he got tested, his results came back negative for both COVID-19 and the flu.

Lots of people seem to be in similar situations right now. Plenty of respiratory viruses are going around, even as flu season dies down and COVID-19 diagnoses decline. Many of these viruses cause cold-like symptoms, so it’s hard to say what any single person has. But human metapneumovirus, which causes symptoms including cough, congestion, and fever, is currently causing a particularly high percentage of positive test results, U.S. Centers for Disease Control and Prevention data show.

If you’re sick with a mystery virus, experts I interviewed said not to worry too much about figuring out what it is. For most routine respiratory viruses, their advice is the same: stay home, rest, take over-the-counter medications if necessary, and call your doctor if you have severe symptoms including a high fever or difficulty breathing.

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