National Park Service officials have received an above-average number of complaints of gastrointestinal illnesses in and around Wyoming’s Yellowstone and Grand Teton national parks.  Reports began around June 7, after members of a tour group in Mammoth Hot Springs, a part of Yellowstone National Park, fell ill, followed by a number of park employees that had come into contact with the group.  Tests confirmed that norovirus was the source of their illness.

Since the initial alert, there have been 100 suspected cases of norovirus among Yellowstone employees and 50 suspected cases in employees at Grand Teton.  An additional 50 visitors come to medical clinics inside Yellowstone presenting similar symptoms.  With an annual three million visitors to Yellowstone and 2.5 million to Grand Teton, officials have emphasized that this has affected only a small percentage of visitors.  Employees are most susceptible, but have been working diligently to sanitize surfaces and limit the spread of the virus.  Some affected employees have been quarantined.

According to the Mayo Clinic, norovirus is a common cause of gastrointestinal illness.  Within 24 to 48 hours of infection, the affected person develops diarrhea, vomiting, and suffering from abdominal pain.  Most people recover without treatment, but dehydration caused by vomiting and diarrhea can result in a need for medical attention.  This is especially true in vulnerable individuals or those with compromised immune systems, such as infants, the elderly, and people with another underlying condition.

The Centers for Disease Control and Prevention have tracked the incidence of norovirus.  Of the known causes of foodborne illnesses in the U.S., norovirus accounts for the largest proportion at 49 percent of all foodborne illness outbreaks.  The CDC also tracks various strains of norovirus, highlighting a new strain detected in Australia that has also affected people in the U.S.  Since it is highly contagious, the CDC recommends washing hands often, washing fruits and vegetables before consumption, cleaning all surfaces and laundry thoroughly, fully cooking shellfish, and avoiding preparing food for others when sick.

The National Park Service is responsible for the care and maintenance of over 400 locations that cover 84 million acres of land and 4.5 acres of oceans, lakes, and reservoirs.  There are 28 thousand employees and 2.4 million volunteers that work to fulfill the mission of the National Park Service.  These groups are most likely to be at risk in this outbreak, but norovirus outbreaks are still relatively rare in national parks.  The greatest risk of norovirus is in a medical facility, restaurant, or cruise ship.