Lyme Disease

What You Need to Know

Lyme disease can cause a rash and flu-like symptoms that can turn into more serious disease if not treated. Not everyone with Lyme disease will have a bullseye rash.
People can get Lyme disease when they are bitten by an infected blacklegged tick. This type of tick is found in California and throughout the eastern U.S.
The best way to prevent Lyme disease is to prevent tick bites: use EPA-registered repellent, check for ticks after being outdoors, and promptly remove any attached ticks with tweezers.

What is Lyme disease?

Lyme disease is an infectious disease caused by bacteria called Borrelia burgdorferi that can spread to people and some other animals through the bite of infected blacklegged ticks.

How do people get Lyme disease?

Illustration of Ixodes tick People can get Lyme disease when a blacklegged tick infected with Lyme disease bacteria bites them and feeds on their blood. Ticks climb onto people when people brush against them, especially outside in tall grass or on rocks and logs. Pets that go outdoors can also pick up ticks and bring them inside where they can bite people. When a tick bites and feeds on a person's blood, it can transmit bacteria and other germs that can make people sick.

There are two types of ticks in the United States that can transmit Lyme disease:

Western blacklegged ticks (Ixodes pacificus) – found in California and along the West Coast of the U.S.
Blacklegged ticks (Ixodes scapularis) – found throughout the eastern U.S.

An infected western blacklegged tick must be attached to a person and feed for at least 24 hours before it can transmit the bacteria that cause Lyme disease. Removing any attached tick as soon as possible can prevent the transmission of disease from the tick.

click to enlarge (image)

A blacklegged tick becomes infected with Lyme disease bacteria when it feeds on a rodent or other animal that is infected. As the tick grows into different life stages (nymph and adult stages), the tick stays infected and can transmit Lyme disease bacteria to people and some other animals (including dogs) when it bites them.

Learn more about how Lyme disease spreads

More About Blacklegged Ticks

Ticks have different life stages (including larva, nymph, and adult). Only nymphs and adult female blacklegged ticks can transmit Lyme disease bacteria to people or animals like dogs. Nymphs pose a greater risk of transmitting Lyme disease because they are tiny (about the size of a poppy seed) and difficult to see, so they may not be noticed and removed promptly.

Nymphs are found in leaf litter and on rocks, logs, tree trunks, or fallen branches under trees in oak woodlands or other shaded natural areas. Adult ticks are found on the tips of tall grasses and shrubs, often along trails. Nymphs are more active in the spring and early summer, while adult blacklegged ticks are more active from fall through early spring.

What are common signs and symptoms of Lyme disease?

Lyme disease may start as a mild illness that might easily be mistaken for other common illnesses like the flu.

Early Signs and Symptoms (3–30 days after tick bite)

Flu-like symptoms

Fever
Chills
Headache
Fatigue
Muscle and joint pain
Swollen lymph nodes

Rash (called erythema migrans or EM)

Expands over time, sometimes with a central clearing giving a "bullseye" appearance
Painless
Varies in shape, size, and color
Looks more like a bruise on darker skin

Early symptoms of Lyme disease can disappear without treatment, but a person can still be infected. If early symptoms of Lyme disease are not treated, they might develop into more severe health problems that can be more difficult to treat.

Note: Not everyone who has Lyme disease gets a rash (especially one that looks like a red bullseye), or it may not be noticeable if it’s on a part of the body that is difficult to see.

Learn more about Lyme disease rashes and see examples

Allergic Reaction vs. Rash

A person may have an allergic reaction to a tick bite that might look like a small rash near the bite area. This reaction may appear soon after the tick bite and be painful, but this is not a Lyme disease rash.

Late Signs and Symptoms (months after tick bite)

Severe headaches and neck stiffness
Arthritis with joint pain and swelling, especially in the knees

Swelling may move from one joint to another and come and go

Paralyzed muscles of the face (facial palsy)
Numbness, tingling, or shooting pains in the arms and legs
Irregular heartbeat or heart palpitations (Lyme carditis)

Although it is rare, Lyme disease can cause death if serious symptoms are not treated.

Learn more about signs and symptoms of Lyme disease

What should a person do if they are concerned about Lyme disease?

A person who is concerned about Lyme disease should talk to a healthcare provider. It's important to share information about any recent outdoor activity or recent tick bite so the healthcare provider can help determine if a person has Lyme disease. A healthcare provider can also order blood tests to help diagnose Lyme disease.

Information to Share with a Doctor

If you notice any new lumps, bumps, rashes, or change of color on the skin

Ticks attached to the skin can be tiny, so it may not be easy to tell if a bump on the skin is a tick
Take a photo of any skin changes so you can show the doctor

If you've been outdoors in the past few days

Include information about where, when, and what kinds of activities you were doing

If you've traveled within or outside of California in the last 30 days and where
If you have pets that go outdoors

How is Lyme disease treated?

Lyme disease can be treated with antibiotics. Prompt antibiotic treatment can cure a Lyme disease infection and prevent complications of late Lyme disease. If treatment is delayed, recovery may take longer.

If a person has had Lyme disease before, they can get it again if they are bitten by another infected tick.

Who is most at risk of getting Lyme disease?

People who spend time outdoors in areas of the U.S. where blacklegged ticks are common are more likely to get Lyme disease. This includes people who live, work, travel, or adventure in:

Northeastern U.S.
Midwestern U.S.
Mid-Atlantic U.S.
Northern coastal region of California
Northern foothills of the Sierra Nevada in California
San Francisco Bay Area and Central Coast of California

About 1 in 3 Lyme disease cases in California are in people who were infected while traveling outside of the state.

The risk of getting Lyme disease also depends on the time of year when blacklegged ticks are more active:

In California

Risk is highest in late fall through early summer (low risk in summer)

See Seasonal Risk Graphic (PDF)

In the Midwest and East Coast

Risk is highest in spring through fall (low risk in winter)

Approximate Risk Map for Lyme Disease Transmission in California and the U.S.

Note: Darker color indicates higher risk. This map is based on an understanding of where Lyme disease cases are reported and where blacklegged ticks are known to occur. 

How can Lyme disease be prevented?

Repellent spray bottle showing percentage of active ingredient (DEET)

The best way to prevent Lyme disease is to prevent ticks from biting you in the first place:

Lyme Disease Prevention

Before you go outside in areas where ticks live, apply an Environmental Protection Agency (EPA)-registered repellent on clothes and exposed skin to keep ticks off you. Use tick repellent with at least 20% DEET as an active ingredient, which is safe when used as directed and is proven to prevent tick bites.

You can also use clothing and gear that has been treated with 0.5% permethrin, a product that will kill or repel ticks. Never apply permethrin to skin.

While outside and after returning indoors from an area with ticks, check your body (and any pets) thoroughly for ticks.
If you find a tick crawling on you or your pet, brush it off (if outside) or flush the tick down the toilet (if inside). If you find a tick attached to the skin, remove it right away with tweezers.
Shower as soon as you can after leaving areas with ticks to wash away any ticks that could be on your body.
Place any clothing you were wearing while in areas with ticks in a hot dryer for 10 minutes to kill ticks crawling on clothing.

Learn more about preventing tick bites

What is the California Department of Public Health doing about Lyme disease?

The California Department of Public Health (CDPH) and local health departments monitor for cases of Lyme disease in California. Lyme disease is a reportable disease, meaning healthcare providers and laboratories are required to report cases of Lyme disease and Borrelia burgdorferi infection to the local health department. CDPH and local vector control agencies also collect and test ticks in California as part of a statewide program to monitor Lyme disease and other tick-borne diseases and understand where infected ticks are present.

More Information