Wastewater Data Show Rising Norovirus Levels Across Much of the U.S.

Wastewater surveillance data show norovirus levels have risen to the high category across much of the United States in recent weeks. Amanda Bidwell, scientific program manager at WastewaterSCAN, stated that national concentrations have remained high over the last 21 days.

The CDC’s NoroSTAT program recorded 1,194 outbreaks from August 1 to May 7, compared with 2,534 during the same period the previous year.

Strain Circulation Dr.

17 has become the predominant strain during the 2024–25 season, accounting for about 75 percent of outbreaks. 4 continues to circulate alongside the newer variant. Both strains produce similar symptoms of vomiting, diarrhea, and stomach cramps that begin 12 to 48 hours after exposure.

Glatt, chief of infectious diseases at Mount Sinai South Nassau, noted that seasonal travel and indoor crowding during hot weather can accelerate spread. The virus transmits through contaminated food, water, surfaces, or direct contact. Dr. Scott Roberts, associate medical director of infection prevention at Yale School of Medicine, said immunity to norovirus is not long-lasting, allowing repeated infections.

Bidwell said monitoring wastewater helps track the virus because most people recover at home without medical testing. Hand washing with soap and water and use of EPA-registered disinfectants remain the primary prevention steps. Yancey added that young children and older adults should watch for signs of dehydration and seek care if symptoms worsen.