Update on shigellosis outbreak among people experiencing homelessness in King County

Public Health – Seattle & King County continues to respond to an ongoing outbreak of shigellosis, mainly among people experiencing homelessness. Since October 2020, Public Health has identified 117 cases that are considered part of this outbreak. Of the outbreak cases, 84% are among people experiencing homelessness; 62% of cases were hospitalized. In comparison, from 2013-2019, most cases of shigellosis reported were among those who were permanently housed. There are also at least four cases from other counties matching one of the outbreak strains. 

In the same timeframe, we have also seen an increase in cases of other diarrheal causing infectious diseases among people experiencing homelessness, particularly cryptosporidiosis and different types of E. coli. We have identified at least 25 cases of cryptosporidiosis in people experiencing homelessness, and 10 of these people were infected with both Shigella and Cryptosporidium germs at the same time.

“We know people experiencing homelessness are at increased risk for a wide range of health problems including outbreaks caused by infectious diseases, such as shigellosis and cryptosporidiosis,” said Elysia Gonzales, Medical Epidemiologist, Public Health – Seattle & King County. “The lack of access to medical care, clean drinking water, toilets, and handwashing facilities contributes significantly to the spread of infectious diseases in this population.”

Public Health has not identified any new cases of shigellosis among people experiencing homelessness in more than two weeks, which is also just over two full incubation periods. This is a promising sign that the outbreak may be tapering off, however, it is too soon to know if the outbreak is ending.

Health risks

Shigellosis and cryptosporidiosis are diarrheal illnesses that spread easily from one person to another. Symptoms may include diarrhea, fever, stomach cramps, nausea, and vomiting. Most people get better with fluids and rest after about one to two weeks and do not typically require medical treatment. Some people can be sick longer or become dehydrated and need medical care and medications. Those with weakened immune systems can develop a more serious or longer illness. People can be contagious even after feeling better.

Both germs spread when someone does not wash their hands well after using the toilet and then contaminates objects, food, or water, and the germs spread especially easily within crowded, unsanitary conditions. Cryptosporidium germs (parasites) spread in the same ways as Shigella germs (bacteria) but are more often associated with drinking contaminated water.

Handwashing with soap and water is the best way to protect yourself and others against germs like Shigella and Cryptosporidium. Alcohol-based hand sanitizers, with at least 60% alcohol, can work to kill Shigella but do NOT work against Cryptosporidium germs. Alcohol-based hand sanitizers do not work well when hands are visibly dirty or greasy. When possible, use soap and water.

It is important for people to contact a healthcare provider or a service provider if people have symptoms such as diarrhea, fever, and stomach cramps, especially if these symptoms continue for more than a few days or become more severe (such as bloody diarrhea or dehydration).

Public Health response

Public Health continues to contact all homeless service providers where someone may have been while infectious; this includes emergency shelters, day centers, supportive housing, food services, and encampments. We look for others with diarrheal illness, refer people to medical care if needed, and provide infection control guidance to prevent further spread of the germs. At this time, no facilities have been identified as a source of spread.  

Public Health has tested some water sources and equipment in decorative fountains within the Seattle downtown area to try to find possible environmental sources of these diseases. Results were all negative for presence of Shigella germs or other signs of fecal contamination, however negative results do not rule out these places completely as a source of spread. 

Public Health is also working with the City of Seattle to improve access to clean water sources, toilets, handwashing stations and additional environmental cleaning in areas where people may be using public areas for toileting purposes. Public Health is also working to decrease access to unsafe water sources that may be contributing to the spread of these germs.

Since the outbreak began, Public Health has provided guidance materials and signage for homeless service providers and businesses that provide services to people experiencing homelessness or oversee water sources near encampments. The Sanitation and Hygiene Guide for Homeless Service Providers has information about special cleaning and disinfection. Public Health also issued a health advisory to healthcare providers in King County to provide information about identifying and treating shigellosis among people experiencing homelessness.

Homeless service sites that suspect any clusters of diarrheal illness should contact Public Health – Seattle & King County at 206-296-4774.

Originally posted May 17, 2021