A new strain of norovirus may be circulating, potentially leaving fewer people with immunity, according to Lynn Roberts, an epidemiologist with the Wisconsin Department of Health Services. This new strain of virus is not uncommon and can lead to larger outbreaks due to less widespread immunity. Immunity to norovirus is short-term, lasting from a few months to about a year on average, making people susceptible to new strains. The CDC reported 91 outbreaks in December, the highest levels in over a decade, with the illness causing 900 deaths, 109,000 hospitalizations, and 19-21 million cases annually in the U.S., mostly among older adults.
Roberts noted in an interview with Wisconsin Public Radio that the previous dominant strain of norovirus in the U.S. has been overtaken by a new strain this year. Norovirus is the leading cause of foodborne illness in the U.S., with just 10 viral particles capable of causing illness, making it easily transmissible. Foods like leafy vegetables, fresh fruits, and shellfish are common sources of norovirus outbreaks according to the CDC. The FDA recently issued multiple oyster recalls due to an increase in norovirus outbreaks nationwide. Because the virus is heat resistant, foods that could be contaminated should be cooked at temperatures higher than 145 degrees Fahrenheit.
Symptoms of norovirus infection are often intense and last for 24-48 hours, including nausea, vomiting, diarrhea, and dehydration. While most people recover within one to three days, the elderly, immunocompromised individuals, and children are at higher risk for complications. The virus is mainly transmitted through contaminated food and surfaces, with the CDC recommending cleaning and disinfecting surfaces regularly. Washing hands with soap and water is advised as hand sanitizer is less effective against norovirus due to the virus’s genetic makeup and its interaction with alcohol-based cleaners.
Dr. Jatin Vyas, an infectious disease professor at the Columbia University Medical School, suggests that changes in the amino acids used to make up the protein shell of the virus can lead to new strains. It is difficult to predict whether these changes will result in the dominant circulating strain. The CDC recommends caution with potentially contaminated foods and regular handwashing to prevent the spread of norovirus. The rising number of cases across the U.S. is a cause for concern, with 91 outbreaks reported in December, the highest levels in over ten years. The CDC and healthcare professionals are urging the public to take preventative measures to protect themselves from the illness.