The Santa Clara County Public Health Department is investigating multiple cases of Shigella within the unhoused community.
Shigella is a highly contagious bacteria that can lead to diarrhea and severe disease in some cases, according to the health department.
"Shigella is an extremely infectious disease," Santa Clara County Public Health Department Assistant Health Officer Dr. Monika Roy said. "It only takes a little bit of the organism to be able to cause disease, so it's easily spread."
The health department said it identified three confirmed cases between June 3 and June 17 and is investigating to see if four other people with Shigella are connected to those cases. Additionally, 18 more suspected cases have been identified.
Most of the cases reported have been linked to people living at Columbus Park in San Jose. The city has brought in additional portable public toilets and hand-washing stations.
"We are beginning to supply drinking water and wash water to folks so that they can stay clean and avoid transmission," San Jose Deputy City Manager Kip Harkness said.
Shigella can be spread by eating or drinking food contaminated with the bacteria or by coming in contact with the bacteria directly from someone who has it or from a shared surface, the health department said.
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For most healthy people, the infection will go away without treatment, the health department said, adding that the risk to the general public is "very low."
County public health nurses and doctors were going into encampments to help educate unsheltered residents in hopes of stopping the spread.
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"We are working aggressively to get testing kits out to all these individuals and get those test kits back, but it is a challenge," Roy said. "It will be difficult to identify every single person that may be affected."