Yes, Lyme disease is present in California. The state reported 904 total cases between 2013 and 2019, making it a real but relatively uncommon risk compared to heavily affected states in the Northeast and Upper Midwest. The disease is transmitted by the western blacklegged tick, which thrives in specific habitats across the state, particularly in northern California’s coastal and wooded regions.
How Common Lyme Disease Is in California
California averages roughly 100 to 150 reported Lyme disease cases per year. That’s a fraction of what states like Connecticut, Pennsylvania, or New York see annually (often thousands of cases each). But the risk is not zero, and it’s concentrated in certain parts of the state, meaning your actual risk depends heavily on where you live and spend time outdoors.
The disease is caused by the same bacterium found in the Northeast, but it reaches humans through a different tick species. In the eastern U.S., the blacklegged tick (sometimes called the deer tick) is the primary carrier. In California, that role belongs to the western blacklegged tick, which has different habitat preferences and lower infection rates. In northern California, only about 1 to 2% of adult western blacklegged ticks carry the Lyme bacterium. Nymphal ticks (the younger, smaller stage) actually carry it at higher rates, typically 2 to 15%, and are harder to spot on your skin.
Where the Risk Is Highest
The western blacklegged tick is found primarily along the Pacific coast, with northern California being the area of greatest concern. Coastal counties with dense oak woodlands, mixed forests, and shaded grasslands provide ideal tick habitat. Research in Santa Barbara County has confirmed that oak woodland and oak savannah environments harbor significant tick populations even in southern California, though overall risk is lower there.
These ticks prefer shady, humid, overgrown areas, especially tall grass and dense vegetation. They are rarely found in open, sunny spots like mowed lawns. If you’re hiking through oak-studded trails, walking in leaf litter beneath tree canopy, or moving through brushy terrain, you’re in prime tick territory. Open chaparral and dry, sun-exposed hillsides carry less risk.
When Tick Exposure Peaks
California’s tick season doesn’t follow the same calendar as the East Coast. Adult western blacklegged ticks are most active during the cooler, wetter months from fall through early spring. Nymphs, which are responsible for most human Lyme transmission due to their tiny size (about the width of a poppy seed), are most active in spring and early summer. This means your risk window in California can stretch from late fall through June or July depending on the region and weather patterns.
The nymphal stage is the most dangerous for a simple reason: these ticks are so small that people often never notice the bite. An adult tick is easier to find during a body check, giving you time to remove it before transmission occurs. A nymph can feed for days undetected.
Symptoms to Recognize
Early Lyme disease in California looks the same as it does anywhere else. The hallmark is an expanding red rash that appears within 30 days of an infected tick bite. This rash doesn’t always form the classic “bull’s-eye” pattern that many people expect. It can appear as a solid red area that slowly expands, and more than one rash can develop on different parts of the body, not necessarily at the bite site.
The rash can also be missed entirely. On darker skin tones, the redness may be harder to see, and if it appears on your back, scalp, or behind a knee, you might never notice it. Along with or instead of the rash, early symptoms include fever, chills, headache, swollen lymph nodes, muscle and joint pain, facial muscle weakness, and occasionally heart irregularities. These symptoms overlap with many common illnesses, which is part of what makes Lyme tricky to catch early, especially in a state where doctors may not be thinking about it as often as their counterparts in Connecticut.
Other Tick-Borne Infections in California
The western blacklegged tick doesn’t just carry Lyme. It can also harbor a related bacterium called Borrelia miyamotoi, which causes a relapsing fever-like illness with recurring episodes of high fever, headache, and body aches but typically no rash. About 0.8% of adult ticks and 1.4% of nymphs in California carry this pathogen. The first confirmed severe case in California was documented in 2021 in an immunocompromised patient.
California also has tick-borne relapsing fever transmitted by a completely different type of tick (a soft-bodied tick found in high-elevation mountain cabins), as well as reportable diseases like anaplasmosis, babesiosis, ehrlichiosis, Rocky Mountain spotted fever, and tularemia. The state requires healthcare providers to report all of these to public health authorities.
Reducing Your Risk at Home and on Trails
If you live near wooded or brushy areas in California, a few changes to your yard can make a real difference. Keep your lawn mowed and decorative plants trimmed. Remove leaf litter and grass clippings. Create a 3-foot barrier of gravel or wood chips between your lawn and any adjacent wild or overgrown land, like chaparral or woodland. Move outdoor furniture and play equipment away from yard edges toward sunnier, more central spots. If you have dogs or cats that go outside, talk to your vet about tick prevention and check your pets daily, especially after they’ve been in brushy areas.
On trails, wear long pants and tuck them into your socks when hiking through grassland or oak woodland. Light-colored clothing makes ticks easier to spot. Use EPA-registered repellent on exposed skin, and consider treating hiking clothes with permethrin, which kills ticks on contact. After any hike in tick habitat, do a thorough body check. Pay close attention to your hairline, behind your ears, underarms, waistband, and behind your knees. Shower within two hours of coming indoors.
If you find an attached tick, remove it with fine-tipped tweezers by grasping as close to the skin as possible and pulling straight up with steady pressure. The California Department of Public Health does not recommend sending the tick to a lab for testing, as the results aren’t reliable enough to guide medical decisions. Instead, note the date you found the tick and watch for symptoms over the following month.