County of Marin Health and Human Services

Lyme Disease (Borrelia burgdorferi)

A suspected or confirmed case must be reported within 7 calendar days to Marin County Communicable Disease and Prevention Control (CDPC) Unit.  Copies of laboratory reports must be submitted with case report.  

For Clinicians:

Lyme Disease Case Report Form 

Ticks and Tick-Borne Diseases

In the past decade Marin County has had very few confirmed cases of Lyme disease (1.2 cases per 100,000 person-years), which makes it a low-incidence Lyme disease area. In 2017, there were no confirmed cases of Lyme disease in Marin County.  In 2016 there were 2 confirmed cases (0.8 cases per 100,000 person-years).  One case was locally acquired and the other was acquired during travel to the east coast. Nationwide 95% of confirmed Lyme disease cases are reported from the 14 states that are considered high-incidence Lyme disease areas (i.e., Connecticut, New Jersey, and Virginia).

Marin County Health and Human Services  tests ticks through the regional Napa- Solano-Yolo-Marin County Public Health Laboratory. In 2017, 1.7 % of Western black-legged ticks (Ixodes pacificus) tested contained the bacteria (Borrelia burgdorferi) that can cause Lyme disease.  Marin/Sonoma Mosquito & Vector Control also regularly tests ticks in Sonoma and Marin County, and an average of 3% of the ticks test positive (compared to more than 30% of ticks tested in Connecticut).

Ticks Submitted to the Napa-Solano-Yolo-Marin County Public Health Laboratory

  2013 2014 2015 2016 2017 Total
Total 220 529 645 708 712 2577
Positive 1 6 12 11 12 42
Negative 188 523 536 588 700 2535
% Positive 0.5% 1.1% 1.9% 1.6% 1.7% 1.6%

*Note: Ticks are submitted by individual residents from various locations across the county, state, and nation.  Sixty eight percent (28 ticks total) of the positive ticks were submitted from Marin County locations.  No geographical trends in positivity rates have been seen. 

The western black legged tick (Ixodes pacificus) and other human biting ticks found in Marin County such as the Pacific Coast tick (Dermacentor occidentalis) may carry other tick-borne diseases. Because of tick-borne disease risk, residents are advised to take precautions to protect themselves from tick bites. Ticks feed by sticking their mouthparts into the skin of their host and sucking blood. Infections such as Lyme disease may be transmitted when the feeding tick is attached for at least a day. The risk of being bitten by ticks may be reduced with the following precautions:

  • Wear long pants and long-sleeved shirts. Tuck pant legs into boots or socks and tuck shirts into pants.
  • Wear light-colored clothing so ticks can be easily seen.
  • Use a repellent registered for use against ticks; always follow label directions.
  • Stay in the middle of a trail and avoid logs, tree trunks, trail margins, brush and grassy areas.
  • Inspect yourself frequently while in tick habitat. Once out of tick habitat, thoroughly check your entire body and pets. Parents should examine their children, especially on the scalp and hairline.
  • Shower and launder clothes soon after activity in tick habitat.

Tick Removal

To reduce the possibility of infection, remove attached ticks as soon as possible. Gently and firmly grasp the tick close to the head and pull it straight out, preferably with a tick tool or with fine-pointed tweezers. The person removing the tick should wash their hands before and after removal and apply antiseptic to the bite area. Insecticides, Vaseline, lighted matches or gasoline should not be used to remove ticks because these techniques are ineffective or unsafe. Anyone who develops symptoms after being bitten by a tick should consult their health care provider. 

Because 24 to 48 hours of attachment to the host are required for infection to occur, early removal can help prevent disease. Painful redness that occurs less than 24 hours after a tick bite and does not expand is likely a local allergic reaction to the tick bite. Early Lyme disease also has a rash but the Lyme disease rash appears three to 30 days after the tick bite, is often painless, and spreads to greater than 5 cm in diameter. The spreading rash can be accompanied by flu like symptoms, such as fever and body aches. Lyme disease is treated with antibiotics and most patients recover without complications, particularly when the disease is diagnosed early.

Useful Lyme Disease Links