For the past month, norovirus has been spreading in the Northeast at the highest levels seen since April of the previous year.

Since late January, the region has been experiencing an average of over 13% positive results for norovirus tests, based on data from the Centers for Disease Control and Prevention. This share is currently higher than any other part of the U.S., but it is lower than the rate in the region at this time last year.

Norovirus tends to be more common during the colder months, typically in late fall, winter, and early spring. Across the country, the rates of norovirus positivity have remained steady at around 10% to 12.5% since the beginning of January. Compared to last year, the peak rates went over 16% in mid-March.

Western states are experiencing the second-highest impact, with a three-week positivity rate of 12% as of Saturday.

Many people call norovirus the stomach flu, but it is not connected to influenza. This virus is known for causing gastrointestinal symptoms such as vomiting, nausea, diarrhea, and stomach pain. There may also be a mild fever and aches.

It’s important to be aware that norovirus can easily spread through hands and surfaces. Even a small number of particles can cause illness, and individuals with the virus release billions of particles in their stool and vomit. The virus has the ability to remain on objects and surfaces for an extended period, potentially lasting for days or even weeks.

According to the CDC, a person who is infected can still spread norovirus even after starting to feel better, possibly for as long as two weeks.

The virus can also be transmitted through contaminated food, leading to it being commonly known as “food poisoning.” It’s important to note that norovirus is the primary culprit behind foodborne illnesses in the nation. Food may become contaminated if fruits or vegetables are cultivated or rinsed in unclean water.

Oysters can also present a norovirus risk if collected from water that is contaminated. At the moment, the FDA recommends that restaurants, retailers, and consumers refrain from selling or consuming certain oysters from Baja California and Sonora, Mexico.

In December, a norovirus outbreak associated with a North Carolina sushi restaurant affected a minimum of 241 individuals.

In the United States, the majority of norovirus outbreaks occur from November to April. Typically, the nation experiences approximately 20 million cases annually.

Unfortunately, there is no cure for the virus, but the CDC suggests staying hydrated by drinking plenty of fluids. Usually, the sickness goes away in a matter of days.