Enlarge / An electron micrograph of norovirus. (credit: Getty| BSIP)

While cold-weather waves of flu, RSV, and COVID-19 are on a merciful decline, another common pathogen seems to be having its moment: norovirus.

The percentage of positive norovirus tests at the end of January has surpassed the peak percentage seen last year in March, according to surveillance data collected by the Centers for Disease Control and Prevention. Though the data suggests the virus may have peaked on a national level, regional data shows cases are still floating upward in the Northeast, Midwest, and Western US, with numbers in the South seemingly sinking.

Norovirus test positivity. (credit: CDC)

Like many infectious diseases, norovirus cases bottomed out amid the pandemic health restrictions and disruptions. But in 2022, the US saw a resurgence to pre-pandemic levels—and by one metric, surpassed them. The CDC’s Norovirus Sentinel Testing and Tracking (NoroSTAT) network, which collects data on norovirus outbreaks from 14 collaborating state health departments, reported that the number of norovirus outbreaks at the end of February 2022 hit a season peak exceeding that of any previous season since surveillance began in 2012.