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,

A nasty stomach bug has been spreading across the country, including California, in recent months—leaving people feeling nauseous, achy or worse.

First came the fires. Then, there was ash and contaminated water. Now, some survivors of the Southern California wildfires are dealing with outbreaks of norovirus and other stomach ailments at a shelter set up to help evacuees.

Three people have tested positive for norovirus amid a cluster of 28, the Pasadena Public Health Department said on Friday.