There has been an outbreak of norovirus at a shelter housing people who evacuated their homes to escape the massive wildfire in Northern California.
Butte County public health spokeswoman Lisa Almaguer said that lab tests confirmed the virus and 21 people who were sick have been quarantined at the shelter in Chico, California, but in an area separate from healthy evacuees.
There are 179 evacuees at the shelter, according to Almaguer.
"There may be reports of similar illness in other shelters, but none are lab confirmed at this time," she said.
Staff mopped floors with bleach Wednesday at the Neighborhood Church in Chico, where a large room has been converted into a makeshift medical care center.
Norovirus is highly contagious and can cause diarrhea, fever and body aches. It spreads commonly when people are in close quarters.
To protect yourself from the virus, health officials said to wash your hands often, rise fruits and vegetables and cook shellfish thoroughly.
NBC Bay Area's Kiki Intarasuwan contributed to this report.