California residents and pet owners in the San Francisco Bay Area have been alerted to an outbreak of a potentially serious disease.
Why It Matters
Berkeley, California, is confronting a notable public health concern following the discovery of leptospirosis—a potentially deadly bacterial infection spread primarily by rats—within a homeless encampment.
Local health officials issued the warning due to increased risks for both residents and pets, particularly dogs, after recent heavy rainfall created conditions that allow the bacteria to survive and spread more easily.
What to Know
City officials confirmed leptospirosis in several rats and at least two dogs near the Harrison Street encampment along Codornices Creek, prompting a public health alert.
Leptospirosis is caused by Leptospira bacteria, which are transmitted through the urine of infected animals—most commonly rats—that contaminates soil and standing water.
Although no human cases have been identified so far, the disease poses serious health risks to both people and animals exposed to contaminated environments.
Dogs face heightened danger because they are more likely than humans to come into contact with puddles and stagnant water. Dr. Monica Gandhi, an infectious disease specialist at UCSF, noted that the illness does not spread between people, making animals particularly vulnerable.
People and animals can become infected when contaminated water or soil enters the body through cuts, the eyes, mouth, or other mucous membranes.
Health officials say the combination of warm weather followed by storms has created ideal conditions for the bacteria, which can survive in soil or water for up to a month—prolonging the risk even after initial exposure.
The city has designated the Harrison Street area as a “red zone” and is urging encampment residents to relocate at least one-third of a mile away to allow for cleanup, rodent control, and safety efforts.
Officials have posted warning signs, conducted environmental testing, and are encouraging pet owners to vaccinate their animals against leptospirosis. Vaccination is also recommended for free-roaming cats, and all pet owners are advised to prevent animals from drinking potentially contaminated water.
Symptoms and When to Seek Care
Anyone who has been in the affected area and experiences flu-like symptoms—such as fever, chills, headaches, muscle aches, or red eyes—should seek medical attention and mention possible exposure to leptospirosis.
Dog owners should be alert for symptoms including vomiting, jaundice, or changes in urination and seek immediate veterinary care if they appear.
What Experts Say
Dr. Peter Chin-Hong of UC San Francisco explained that exposure risk increases wherever rat urine combines with flooding or rainfall, especially in warm conditions.
Dr. Gandhi emphasized that infection requires direct exposure to contaminated environments and warned that symptoms can appear long after contact, making it important for clinicians to ask about animal or environmental exposure.
Berkeley’s public health officer, Dr. Noemi Doohan, urged residents and pet owners to avoid wading in or drinking from nearby water sources, including Codornices Creek, and to keep pets away from sick or dead animals.
What Happens Next
Berkeley officials have launched an ongoing investigation, with cleanup and rat eradication efforts expected to continue for at least 30 days—the typical length of time the bacteria can survive in soil.
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