Homeless Encampments Characteristics Critical in Reducing Vector-Borne Disease Potential

As of January 2019, a survey of homeless people in Alameda County, CA, documented 8,022 homeless individuals countywide, including 6,312 unsheltered people. Dozens of homeless encampments exist throughout the County, and most lack sanitation facilities (e.g., rodent-proof garbage storage and weekly waste removal; sanitary toilets; and running water for hand washing, showering, or laundry). This situation represents a breakdown of the sanitation interventions that can lead to the outbreak of vector-borne disease (e.g., 2020 outbreaks of flea-borne typhus in southern California). Some characteristics of surveyed encampments make them more or less suitable for Norway rat population establishment and the exhibition of problems associated with rodent ectoparasites. Many urban encampments are in parts of Oakland that have old infrastructure including sewers that support an endemic population of Norway rats and where there may be undetected sewer breaks that allow these rats into these homeless encampments. Anecdotally, before the introduction of unmanaged leftover food sources (garbage), rats would go virtually unnoticed due to their low population, but with a regular supply of food, their populations apparently skyrocketed. Unmanaged rodent populations at homeless encampments are a major public health concern for local public health, particularly considering that ectoparasites such as fleas are potential rodent-borne disease vectors.