County of Marin - News Releases - Legionnaires' Disease

For Immediate Release
September 01, 2015

County Continues to Monitor Legionella Outbreak

Medical officials assist with Legionnaires’ disease at San Quentin

San Rafael, CA – As San Quentin State Prison takes steps to return to normalcy following an outbreak of Legionnaires’ disease, medical professionals from the County of Marin’s Department of Health and Human Services continue to monitor the situation and offer advice.

The prison, located on the shore of San Francisco Bay just east of Larkspur, has experienced six confirmed cases of the severe form of pneumonia known as Legionnaires’ disease and 85 people experiencing similar symptoms. Seven of the afflicted people were hospitalized.

Drs. Matt Willis and Bob Benjamin, the County’s Public Health Officer and Deputy Public Health Officer, respectively, have been in steady communications with officials at the prison since August 27. The doctors are part of a response effort comprised of San Quentin personnel, state and federal corrections officials, and state and local environmental health sources.

The disease, cause by aerosolized water-borne bacteria, is not spread from person to person and the community outside the prison is not at risk. Residents of nearby San Quentin Village were provided public education fliers about the latest updates from the prison, including confirmation by the Marin Municipal Water District that the village water supply is independent of the prison water supply. No water use warnings were issued for San Quentin Village.

The illness can begin up to 10 days after infection, and the incubation period is 2-10 days. Although measures have been taken to mitigate any additional exposure, “There may be an increase in cases for a few more days, from infections that occurred before the water was shut off last Thursday,” Willis said. To date there have been no confirmed Legionnaires cases among guards, staff, family members living on prison grounds or visitors.

The primary focus for County Health officials has been the safety of the wider Marin community. Willis released a public health advisory, alerting clinicians throughout Marin that patients who are staff or visitors to San Quentin may have been exposed to Legionella and making recommendations on testing, treatment, and reporting such cases.

The California Department of Corrections and Rehabilitation (CDCR) is overseeing the environmental testing process at the prison to find the source of the outbreak. Willis said the source is investigated in two ways: 1) environmental and water sampling throughout the facility, and; 2)  epidemiologic assessment looking at each case to determine if they have exposures in common, such as a single shower area.

“Both of these processes are ongoing in the San Quentin outbreak, are early in their course, led by CDCR, and have not revealed a definitive source,” Willis said. “This is why most water sources remain turned off and they are relying on external water.”

Legionnaires’ disease is caused by Legionella pneumophilia, a bacteria transmitted by aerosolized contaminated water particles, most often from shower, air conditioning cooling towers, evaporative condensers, humidifiers, whirlpool spas, hot tubs and decorative fountains. Warm water temperatures with stagnation are conducive to legionella growth.

San Quentin is the lead agency for media contacts. Public Information Officer Lt. Samuel Robinson can be reached at 415-455-5008 or To reach the California Department of Corrections and Rehabilitation state office, contact Public Information Officer Dana Simas at 916-445-4950 or


Dr. Matthew Willis
Public Health Officer
Health and Human Services

3240 Kerner Blvd.
San Rafael, CA 94901
(415) 473-4163
Email: Dr. Matthew Willis
Marin HHS website