() The highly contagious outbreak of norovirus has sickened at least 28 people staying at a California wildfire evacuation shelter. 

Public health officials said the gastrointestinal illness has been detected among a group of people at the Pasadena Convention Center, one of the many structures that were converted into evacuation shelters after the wildfires in Los Angeles County displaced thousands, reported CBS News. 

The norovirus, also called the “stomach bug,” causes acute gastroenteritis, an inflammation of the stomach or intestines, and spreads quickly especially in close quarters, according to the Centers for Disease Control. 

Symptoms include vomiting and diarrhea, the CDC said. While most people get better within 1 to 3 days, they can still spread the virus for a few days after.

The virus spreads via direct contact, eating food or drinking liquids that are contaminated with norovirus, and touching contaminated objects or surfaces and then putting your unwashed fingers in your mouth, according to the agency. 

More than 12,000 homes and businesses have been burned in the massive fires which have forced many into shelters.

The Pasadena Health Department said it will install more handwashing stations, implement more frequent restroom cleaning and utilize disinfectants strong enough to kill the virus, CBS reported.