Roughly 170 people who have visited Yosemite national park in recent weeks have suffered upset stomachs and diarrhea, symptoms that park officials say are consistent with norovirus.

Two of those cases have been confirmed as norovirus, park officials say. The park spokesman Scott Gediman issued a written statement that most of those who fell ill had spent time in Yosemite Valley around the first week of January.

The San Francisco Chronicle reported last week that a dozen recent park visitors reported illnesses, triggering widespread inspections of the park’s food service and hotel facilities from federal health officials.

Norovirus is a contagious stomach illness that’s spread by contact with those infected or contaminated surfaces, according to the US Centers for Disease Control and Prevention.

The spokesman said the park was undertaking “extensive cleaning and enhanced sanitation protocols” to address the outbreak.

In 2017, roughly 190 students from Santa Monica were reported to have been infected with norovirus after taking a trip to Yosemite. And in 2012, an outbreak of hantavirus, which is spread mostly by rodents, infected 10 people and killed three.

The recent reports of norovirus are the latest in a rash of problems and bad publicity at California’s famous national park, which receives millions of annual visitors.

Last year, complaints and bad reviews stacked up from visitors who were unhappy with food and the long waits for shuttle services. This year, inspectors revoked the prestigious four-star rating for the park’s once-lustrous Ahwahnee Hotel after guests complained of bad food and shabby service, the Chronicle reported.

The food and shuttle services, as well as the hotel, are operated by Aramark, a Philadelphia-based company valued at $140m annually.