Shigellosis outbreak among persons experiencing homelessness-San Diego County, California, October-December 2021

Abstract

During October 2021, the County of San Diego Health and Human Services Agency identified five cases of shigellosis among persons experiencing homelessness (PEH). We conducted an outbreak investigation and developed interventions to respond to shigellosis outbreaks among PEH. Confirmed cases occurred among PEH with stool-cultured Shigella sonnei; probable cases were among PEH with Shigella-positive culture-independent diagnostic testing. Patients were interviewed to determine infectious sources and risk factors. Fifty-three patients were identified (47 confirmed, 6 probable); 34 (64%) were hospitalised. None died. No point source was identified. Patients reported inadequate access to clean water and sanitation facilities, including public restrooms closed because of the COVID-19 pandemic. After implementing interventions, including handwashing stations, more frequent public restroom cleaning, sanitation kit distribution, and isolation housing for ill persons, S. sonnei cases decreased to preoutbreak frequencies. Improving public sanitation access was associated with decreased cases and should be considered to prevent outbreaks among PEH.

Keywords: Shigella; community outbreaks; dysentery (bacillary)hand hygiene; hygiene-personal.

Figure 1.

Shigellosis cases in persons experiencing homelessness by week of illness onset* (N = 53). *When onset date is unavailable, specimen collection date is used.

Figure 2.

Geographic location* of patient living areas in San Diego City by whole genome sequencing cluster, with sanitation facilities and approximate densities of encampment sites. *Geographic locations of patient living locations are approximated to decrease identifiability. ^†Areas with higher density of encampments are indicated in deeper purple. ^±Added or relocated in response to this outbreak.

Figure 3.

Total monthly precipitation in inches, National Oceanic and Atmospheric Administration, San Diego area, August–December 2021, compared with August–December 1990–2020. *The footnote with this figure is to indicate that there was no rainfall in November (refers to the asterisk on the x axis).

Figure 4.

Shigella sonnei and Shigella flexneri cases in persons experiencing homelessness by month, San Diego County, 2018–2021*. *When onset date is not available, specimen collection date is used.