Norovirus, a highly contagious stomach bug that typically affects individuals during the winter months, is seeing a slow rise in cases in the United States. The virus, which causes acute gastroenteritis and leads to symptoms such as vomiting and diarrhea, has experienced a surge in activity in early 2023, with cases peaking in February and March. Although norovirus activity remained low during the summer, experts are warning that it is expected to increase as the winter and holiday season approaches.
Noroviruses are a group of viruses that are responsible for causing millions of cases of vomiting and diarrhea in the U.S. each year. Despite being commonly referred to as the “stomach flu,” norovirus is not related to the flu caused by influenza viruses. It is a highly contagious viral infection that affects a large number of Americans annually, leading to emergency room visits, hospitalizations, and even deaths.
After a decrease in norovirus outbreaks during the COVID-19 pandemic, cases spiked during the past winter and remained high throughout the spring of 2023. England also experienced a severe norovirus season, with cases reaching the highest levels seen in over a decade. Additionally, norovirus outbreaks on cruise ships reached their highest levels in 11 years, with more outbreaks reported in the first six months of 2023 than in any full year since 2012.
As the temperature drops and the winter season approaches, there has been a slow increase in norovirus cases. Recent data from the U.S. Centers for Disease Control and Prevention (CDC) shows that the rate of positive norovirus tests has increased from September and October, although it is lower than the peak in March. While norovirus activity typically decreases in the summer and ramps up in the fall and winter, there was a small uptick in cases in August this year.
Between August and October 2023, there have been 100 reported norovirus outbreaks in the U.S., compared to 71 during the same period last year. However, according to the CDC, the reported outbreaks and cases remain within the expected range for this time of year. Experts predict that norovirus will increase again in late 2023 and early 2024, as the majority of outbreaks historically occur between November and April.
Norovirus spreads easily through the fecal-oral route, where bacteria or viruses shed in stool end up on hands, surfaces, and eventually in the mouth of an individual who ingests them. It can be transmitted directly from an infected person or indirectly through contaminated surfaces, objects, foods, or drinks. Norovirus is highly infectious, with just a few virus particles being enough to cause infection. It is known to cause explosive outbreaks due to its ability to transmit with a small number of particles.
Symptoms of norovirus include vomiting, diarrhea, nausea, stomach pain, cramps, headache, body aches, and a low-grade fever. They usually develop within 12 to 48 hours after exposure and typically last for a few days. While most individuals experience mild symptoms, babies, the elderly, and the immunocompromised are at higher risk of developing severe or prolonged symptoms. Outbreaks commonly occur in settings such as schools, daycares, healthcare facilities, nursing homes, and cruise ships.
