Norovirus In Michigan: Why Cases Are On The Rise

Shannon Antinori
Updated ·4 min read

MICHIGAN — Michigan health officials are keeping an eye on a steady increase in cases of the highly contagious stomach bug known as the norovirus, and oysters from Canada likely played a role in a spike in cases in some areas.

In the first three months of 2022, a total of 720 cases of norovirus have been reported statewide. For all of 2021, Michigan reported 593 cases of norovirus. In 2020, there were even fewer — 583 cases for the entire year.

The leading cause of food-borne illness in the country, the norovirus causes bouts of vomiting and diarrhea that can sicken entire households.

Like other contagious illnesses in the era of masks and social distancing, norovirus outbreaks all but stopped completely at the height of the COVID-19 pandemic, according to federal health data — possibly because most people steered clear of the places where the norovirus typically spreads.

But with the easing of coronavirus restrictions came an uptick in cases of the norovirus, an aggressive virus that can easily contaminate food and water.

That’s one conclusion of Dr. Robert Atmar, a professor of medicine and infectious diseases expert at Baylor College of Medicine in Houston, who discussed the increase in norovirus cases with NBC News.

The norovirus causes inflammation of the stomach or intestines known as acute gastroenteritis. People typically become ill within 12 to 48 hours of exposure and recover within 1 to 3 days. Anyone with the norovirus should stay home for 24 hours after experiencing vomiting or diarrhea.

It takes only a few of the billions of microscopic norovirus particles to make a person sick.

The norovirus is spread a number of ways, including through vomit and feces particles that may remain on a person’s hands or on surfaces during food preparation. It also can come from contaminated water used for irrigation of fruit and vegetable crops — or if food, such as oysters, is harvested in contaminated water.

Outbreak hits U.S.

The most recent example of the latter: As of Monday, 91 people had been sickened after eating oysters distributed in at least 13 states, though the U.S. Food and Drug Administration said more states could be affected by further distribution.

The oysters were harvested from a specific bay in British Columbia, the Centers for Disease Control and Prevention said. The majority of those sickened after eating the oysters were in Canada, where at least 279 illnesses have been reported.

In the United States, illnesses have struck mainly in three states:

But even before the oyster-related outbreaks, the norovirus was making a comeback. Data collected by the CDC's National Outbreak Reporting System shows that 448 norovirus outbreaks were reported from August 2021 to March 2022, compared with 78 outbreaks during the same period the previous year.

The number of outbreaks increased from 10 or fewer per week from August until mid-November, when they rose to near 30 before falling again, and then spiked to around 60 outbreaks in February.

State health departments in Massachusetts, Michigan, Minnesota, Nebraska, New Mexico, Ohio, Oregon, South Carolina, Tennessee, Virginia, Wisconsin and Wyoming reported norovirus cases during the most recent seven-month period.

Agencies aren’t required to participate in the norovirus surveillance system, which the CDC says makes it impossible to estimate the true number of norovirus cases. Many cases don’t require a visit to the doctor’s office, and most hospitals and other health care providers don’t test for it, the agency says.

Symptoms such as vomiting, diarrhea, nausea and stomach cramps usually appear from 24 to 48 hours after exposure. People are contagious for up to two weeks after the point they start feeling ill.

Prevent the spread of the norovirus

The best thing to do is to prevent its spread. Wash your hands the right way, for at least 20 seconds under hot, soapy water, taking care to scrub under nails and between your fingers. Also, clean up food preparation surfaces with diluted bleach.

Quick bouts of gastrointestinal norovirus illnesses are often referred to as the “stomach flu,” though that’s technically incorrect. Influenza is an infection of the respiratory system.

This article originally appeared on the Across Michigan Patch