Nearly two dozen people who evacuated to escape the devastating Camp Fire in Northern California have been sickened by a contagious virus that has spread through an emergency shelter, officials say.

Lisa Almaguer, a spokeswoman for the Butte County Public Health Department, said Thursday in a statement that 21 people being housed at the Chico Neighborhood Church Shelter have tested positive for norovirus, an extremely contagious virus known to spread easily, causing vomiting and diarrhea.

Earlier, Almaguer had told the Sacramento Bee that the virus may have also sickened evacuees at a second shelter in nearby Oroville, but said that the diagnoses had not been lab confirmed.

The evacuees fled last week from the Camp Fire, which started Nov. 8 near Pulga, a small community surrounded by the Plumas National Forest. High winds and dry conditions sent the flames raging through Paradise, a town of 27,000 not far from Sacramento, killing at least 56 people. Many are still missing.

Video: Do you know about the norovirus? (Centers for Disease Control and Prevention)

Almaguer, with the county health department, said in a statement to The Washington Post that there are nearly 180 evacuees at the shelter in Chico.

“Butte County Public Health is implementing measures to decrease the spread of illness by isolating people with symptoms from the well people — this includes providing separate bathroom facilities for those who are ill,” it stated.

Almaguer said even in cases in which illnesses have not been confirmed as the norovirus, “we are taking all necessary prevention measures to keep those who are ill separate from those who are well.”

Rich Montgomery, one of the evacuees, told the Sacramento Bee that he had seen someone “puking into a toilet” and said that health officials "want us to keep washing our hands and not shake hands and use Purell before dinner.”

Norovirus can be spread through contaminated food or water, contaminated surfaces or having direct contact with someone who has the virus, according to the Centers for Disease Control and Prevention. The CDC states that symptoms include stomach pain, diarrhea, nausea and vomiting, and sometimes a fever and headache, but the condition usually begins to clear up within several days.

To help prevent the spread, the CDC urges people to wash their hands thoroughly — especially during and after infection — and to disinfect hard surfaces, wash laundry and avoid direct contact with those who are still contagious with the virus.

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