Outbreak of Gastrointestinal Illness Sickens 170, Associated with Visits to Yosemite National Park

Yosemite National Park officials and the National Park Service Office of Public Health (OPH) are investigating an outbreak of a highly contagious gastrointestinal illness, following dozens of reports of people becoming ill within days of visiting Yosemite Valley. The gastrointestinal illness outbreak has reportedly sickened 170 people who visited or worked at the park on or around the first week of January 2020, and is reportedly consistent with norovirus, a highly contagious virus that causes vomiting and diarrhea. According to a news release posted on the National Park Service website on January 16, there have been just two confirmed cases of norovirus, but the “overwhelming majority of the reported cases [of the gastrointestinal illness] are consistent with norovirus.”

What is Norovirus?

Norovirus is a highly contagious virus that spreads very easily from person to person, either through direct contact with an infected person, by drinking liquids or eating food that is contaminated with norovirus, or by touching a surface or object that is contaminated with the virus. The National Park Service reports that the symptoms of norovirus typically emerge between 12 and 48 hours after exposure and may include nausea, vomiting, diarrhea, severe stomach cramps and dizziness. Norovirus is the leading cause of gastroenteritis in the United States and the U.S. Centers for Disease Control and Prevention (CDC) estimates that the virus is responsible for more than half of all food-borne disease outbreaks each year. The CDC also reports that up to 1.9 million outpatient visits, 400,000 emergency department visits, 71,000 hospitalizations and 800 deaths are associated with norovirus annually.

Recommendations from the National Park Service

According to the National Park Service news release, 170 people have reported experiencing a gastrointestinal illness with norovirus-like symptoms and two people were hospitalized with the virus. The National Park Service reports that both visitors and Park staff were among the individuals affected by the outbreak and that there has been a decline in new cases since the original notice. Yosemite National Park, OPH and other public health agencies have joined together to carry out extensive cleaning and increased sanitation protocols at Park facilities to prevent additional cases of gastrointestinal illnesses. In the meantime, the National Park Service notes that Park visitors can prevent the spread of norovirus by:

  • Washing their hands frequently with soap and water (or an alcohol-based hand sanitizer that contains at least 60% alcohol) for at least 20 seconds; and by
  • Avoiding sharing food or drinks with other people, especially when either person is sick.

People with weakened immune systems are extremely vulnerable to norovirus, but healthy individuals can also become ill if they are exposed to the virus. If you have fallen ill with a norovirus-like gastrointestinal illness, the Park Service recommends that you stay hydrated, limit your contact with others to avoid spreading the illness, and contact your healthcare provider with any questions or concerns.

Prior Outbreaks at Yosemite National Park

This isn’t the first time there has been an outbreak of illness at Yosemite National Park. In 2015, some of the campgrounds at Yosemite National Park were closed temporarily after a young girl was infected with the plague. Park officials discovered two dead squirrels that also tested positive for the plague, a serious disease that humans can contract from infected rodents or their fleas. Three years before the plague scare, there was an outbreak of hantavirus at the Park, which resulted in a total of eight illnesses, including three deaths. According to Park officials, the outbreak occurred because of an infestation of deer mice in the “Signature” tent cabins of Curry Village. Several lawsuits were filed against the National Park Service as a result of the hantavirus outbreak, which officials estimate may have resulted in as many as 230,000 guests being exposed to the virus.