Gastrointestinal Illness Outbreak at Yosemiite National Park Has Sickened 170 People

Officials from Yosemite National park are investigating an outbreak involving highly contagious gastrointestinal illnesses, following dozens of reports involving individuals becoming sick within days of visiting Yosemite Valley.

The Yosemite National Park Service announced the launch of a gastrointestinal illness outbreak investigation on January 16, to determine the cause of at least 170 visitor illnesses, including two hospitalizations that resulted in a norovirus diagnoses.

Norovirus is a viral gastrenterisitis condition which often originates in contaminated food or water, causing inflammation of the stomach, intestines or both. The infections are highly contagious and can be transmitted by an infected person or touching a contaminated surface.

Yosemite’s announcement indicates 170 individuals have reported falling ill with norovirus-like symptoms and two visitors were diagnosed with norovirus. Officials state that both visitors and Park staff were among those to have fallen ill, with the majority of the illnesses occurring in the first week in January.

The National Park Service Office of Public Health (OPH) opened an investigation and determined many of those who became sick spent time in the main visitor area at Yosemite Valley, however the exact source of contamination has not been determined.

The investigation into the highly contagious outbreak has prompted Yosemite National Park to undergo an extensive cleaning and enact enhanced sanitation protocols at park facilities.

OPH and local health officials are warning visitors to help prevent the spread of norovirus by frequently washing hands, avoid sharing drinks and food with other people, and to contact healthcare providesr as soon as possible if symptoms appear.

Norovirus is the leading cause of gastroenteritis in the United States. The U.S. Centers for Disease Control and Prevention (CDC) estimates norovirus is responsible for more than half of all food-borne disease outbreaks each year. The virus can be contracted by eating food or drinking liquids that have been contaminated and by touching an object or surface that has been infected with the virus and then touch your nose, mouth, or eyes. The virus is extremely contagious, and can survive in severe temperatures in water and on land.

The CDC estimates norovirus causes an average of 800 deaths annually, 56,000 to 71,000 hospitalizations, 400,000 emergency department visits, and between 1.7 and 1.9 million outpatient visits. Worldwide, norovirus is estimated to cause over 20 million illnesses per year.

Although healthy individuals are still susceptible to the virus, people with weakened immune systems are extremely vulnerable. The virus causes an individual’s stomach and large intestines to become inflamed, which usually leads to symptoms such as nausea, vomiting, diarrhea, dizziness, and severe stomach cramps.

In 2015, Yosemite National park was forced to temporarily close some of the campgrounds after a young girl was infected with the plague. In addition to the human illness, officials also discovered two dead squirrels that also tested positive for the plaque, requiring the campgrounds to be sprayed for fleas in rodent dens that could be carriers.

This 2015 Yosemite park outbreak involved infected rodents, and came three years after a similar outbreak of hantavirus during the summer of 2012, which was linked to the ability of rodents to infiltrate the “Signature” cabins of Curry Village. Those cabins were dismantled and a number of hantavirus lawsuits were filed against national park system.