Norovirus in the Camp Fire Shelters, California, 2018

The Camp Fire, California's deadliest wildfire, burned from November 8 to 25, 2018, in Butte County, home to about 230,000 people, 18% of them below the federal poverty level.

Nongovernmental organizations opened nine shelters — eight in Butte County, one in Glenn — for about 1,100 evacuees, some living indoors and others in the shelters' parking lots. On November 10, two shelters reported acute gastroenteritis — vomiting and diarrhea. Suspecting norovirus, a common cause of shelter outbreaks that is highly contagious and resists several disinfectants, the Butte County Public Health Department and the California Department of Public Health began active surveillance.

The outbreak

GII.4 is the most common norovirus genotype in the United States and is associated with more hospitalizations and deaths.

Norovirus cases by date of onset in the Camp Fire shelters. CDC

What the teams found

From November 17, state and county teams checked case counts and inspected infection prevention and control (IPC), adapting CDC's Shelter Assessment Tool. Of six longer-term shelters, three needed help setting up isolation areas, three had staff who knew little about norovirus control, three needed separate toilets for the sick, and two needed round-the-clock professional cleaning. Handwashing before meals and at the doors was observed at 100% in one shelter but 0% to 50% in the other five.

Many evacuees and staff didn't know that norovirus needs soap and water — hand sanitizer is not enough.

The response

Working with the shelters' organizations, the Emergency Medical Services Association of California, the U.S. Public Health Service Commissioned Corps and local medical providers, the health departments:

• screened everyone for illness at registration and encouraged screening at every entry, instead of relying on people to report being sick;
• extended surveillance and isolation to parking-lot evacuees, staff and volunteers, not just those indoors;
• set up separate isolation areas, toilets and handwashing for the sick, and delivered meals to them; the state's emergency operations center sent staffed isolation tents;
• pushed for 24-hour cleaning, daily trash removal and an end to self-service food and drink, with disinfection by a bleach-based or EPA List G product;
• repeated IPC training often, because shelter staff turned over quickly — and helped shelters in neighboring Sutter County, where gastroenteritis was also spreading.

No new cases began in the five remaining shelters after November 30. The original shelters closed in early December, and a new one opened for the remaining evacuees, with surveillance continuing.

Lessons

The fire's damage to roads and hospitals knocked out the systems that normally prevent illness — medical care, cleaning, trash collection, protective equipment, surveillance support. Shelters had to be created fast by organizations with few resources; local public health staff were quickly exhausted; and even after state help arrived, poor internet, printing and communication slowed things down. The true number of cases was probably higher: few staff could help with early surveillance, and sick shelter workers were not always counted.

With wildfires increasing in the western United States, more large-scale sheltering is likely — and, the authors wrote in 2020, the arrival of COVID-19 made shelter outbreaks an even greater risk. Local, state and federal public health agencies and relief organizations should plan ahead so that illness surveillance and infection control start the moment a shelter opens, planned or not.

Sources

Based on Karmarkar E, Jain S, Higa J, et al., "Outbreak of Norovirus Illness Among Wildfire Evacuation Shelter Populations — Butte and Glenn Counties, California, November 2018," MMWR Morbidity and Mortality Weekly Report volume 69, number 20, Centers for Disease Control and Prevention; a work of the United States government in the public domain.