RSV, respiratory syncytial virus, usually peaks in December and January while infecting the nose, throat and lungs, usually causing mild, cold-like symptoms, the CDC says. Those symptoms make it difficult to distinguish it from the common cold, COVID-19, or influenza.

For the week ending Jan. 25, seasonal flu activity remains high and increasing. Clinical laboratories tested 129,378 specimens for flu viruses. Of these, 29.4% were positive. Among the positive results, influenza A accounted for 36,471 (95.9%) of positive flu cases, and influenza B accounted for 1,571 (4.1%).