Norovirus, computer illustration

The highly contagious norovirus is making a comeback after receding during the height of the COVID-19 pandemic. The Centers for Disease Control and Prevention reported in the latest Morbidity and Mortality Weekly Report that the number of cases in the 2021 to 2022 surveillance period were nearly triple those during the previous year.

A research team led by Anita K. Kambhampati, MPH, found during the 2021 to 2022 surveillance year the Norovirus Sentinel Testing and Tracking Team (NoroSTAT) participating states reported 992 outbreaks of norovirus to the CDC. By comparison, the same states reported 1,056 cases and 343 cases in 2019 and 2020 years respectively.  The characteristics of the norovirus outbreaks reported by NoroSTAT participating states during the 2021 to 2022 period were similar to those reported in prepandemic years. More than 80% of the outbreaks were due to person-to-person spread, while just under 60% of outbreaks occurred in long-term care settings. 

“Nonpharmaceutical interventions implemented during the COVID-19 pandemic were likely effective in preventing outbreaks of other infectious diseases, including norovirus,” the report stated “As the use of nonpharmaceutical interventions has relaxed, norovirus outbreak incidence has returned to levels similar to those during prepandemic surveillance years.” 

Norovirus is a highly contagious virus which causes vomiting and diarrhea, according to the CDC. Patients typically are infected by coming into close contact with someone who has the virus, consuming contaminated food or water or touching contaminated surfaces and then putting unwashed hands in their mouths. Transmission of the virus can be prevented by handwashing with hot, soapy water, avoiding food preparation for two days after the development of symptoms and properly cleaning and disinfecting contaminated surfaces. 

Older adults are at especially high risk for developing severe symptoms from the virus. It is estimated that the vast majority of norovirus-associated deaths (90%) in the U.S. occur among people 65 and older.