As yet, Lyme disease has not been widely reported in California. There were 139
reported cases in 1999 and 104 in 2000 (extensive statistical data and links to
more can be found at
However, there is some concern that incidents have been underreported, and the
number of cases may, in fact, be much higher. That said, Northern California is
one of the places in the USA where you are definitely at risk for exposure to
Lyme disease and other tick-borne diseases.
A good general description of the disease, how to avoid exposure, how to
recognize it and what sort of treatment is available is summarized in the
following text drawn from http://www.astdhpphe.org/infect/lyme.html.
Lyme disease is a rapidly emerging bacterial infection that is spread to people
by the bite of infected ticks.
Lyme disease can cause a rash, flu-like symptoms, and aching joints.
Lyme disease can be treated with antibiotics. Without treatment, Lyme disease
can cause serious, long-term health problems.
To prevent Lyme disease: 1) protect yourself from tick bites, 2) remove
attached ticks promptly, and 3) get early diagnosis and treatment.
What is Lyme disease?
Lyme disease is an infection transmitted by the bite of certain, very small,
infected ticks. Lyme disease gets its name from the town of Lyme, Connecticut,
where the illness was first identified in the United States in 1975.
What is the infectious agent that causes Lyme disease?
Lyme disease is caused by a corkscrew-shaped bacterium, or spirochete, called
Borrelia burgdorferi. Ticks infected with the bacterium spread the disease to
Where is Lyme disease found?
Cases of Lyme disease have been reported by nearly every state in the United
States, but the disease is concentrated in the east coastal states, the north
central states, and northern California. Connecticut, Rhode Island, New York,
New Jersey, Delaware, Pennsylvania, Maryland, and Wisconsin account for about
90% of all cases.
In the Northeast and Great Lakes region, Lyme disease is spread by the black-
legged tick, which lives in wooded areas, grasslands, and yards. In the Pacific
Northwest, the disease is spread by the western black-legged tick. In the
Southeast, the disease is thought to be spread by the black-legged tick.
How do people get Lyme disease?
Ticks become infected with the Lyme disease bacterium by feeding on infected
animals, such as mice, chipmunks, and other wild rodents. Lyme disease is
passed to humans and other animals when a tick infected with the bacterium
bites the person or animal and stays attached long enough (usually more than 36
hours) to take a blood meal.
The tick that spreads Lyme disease has a 2-year life cycle, and feeds once in
each of its three life stages -- larvae, nymph, and adult. In the tick's larvae
stage, it is tan, the size of a pinhead, and feeds on small animals like mice.
During the nymph stage, the tick is the size of a poppy seed, beige or
partially transparent, and feeds on larger animals such as cats, dogs, and
humans. Adult ticks are black and/or reddish and feed on large mammals such as
deer, dogs, and humans.
What are the signs and symptoms of Lyme disease?
The early stage of Lyme disease is usually marked by one or more of these signs
Chills and fever
Muscle and/or joint pain
Swollen lymph glands
A characteristic skin rash, called erythema migrans
The skin rash is a red circular patch about 2 inches in diameter that appears
and expands around the site of the tick bite. The center may clear as it
enlarges, resulting in a "bulls-eye" appearance. The rash may be warm, but it
usually is not painful or itchy.
Some infected people do not recognize the early symptoms and are diagnosed only
after complications occur.
What complications can result from Lyme disease?
Persons who did not have or did not recognize the early symptoms and who did
not receive treatment can end up with serious complications:
Arthritis (swelling and pain) in the large joints, which can recur over many
Nervous system problems, such as numbness, meningitis (fever, stiff neck, and
severe headache), and Bell's palsy (paralysis of the facial muscles, usually on
Irregularities of the heart rhythm
How soon after exposure do symptoms appear?
Early symptoms can develop within a week to a few weeks of the tick bite. Other
symptoms can appear weeks, months, or years later.
How is Lyme disease diagnosed?
Lyme disease is diagnosed by a physical examination and medical history. The
clinical diagnosis is supported by laboratory testing.
Diagnosis of Lyme disease can be difficult. Current tests are not completely
accurate, and the symptoms can mimic those of other diseases. Diagnosis is
easiest when there is a skin rash.
Who is at risk for Lyme disease?
Lyme disease can affect anyone. Persons who spend time in brushy and wooded
areas are at increased risk of exposure. The chances of being bitten by a tick
are greatest during times of the year when ticks are most active. Deer ticks in
the nymph stage are active from mid-May to mid-August. Adult ticks are most
active in mid- to late fall and early spring.
What is the treatment for Lyme disease?
Lyme disease is treatable with antibiotics taken for 3 to 4 weeks. More
difficult cases may require longer treatment and combinations of drugs. Re-
infection from tick bites is possible after treatment.
How common is Lyme disease?
Lyme disease is the most common disease spread by ticks in the United States.
More than 16,000 cases were reported by 45 states in 1996. However, because of
considerable under-reporting and misdiagnosis, the actual number of cases is
probably several times higher.
Is Lyme disease an emerging infectious disease?
Yes. Lyme disease is a rapidly emerging infectious disease. Since it was first
recognized in the United States in 1975, reports of Lyme disease have increased
substantially, and the disease is now found in several regions of the country.
Factors contributing to the rise in Lyme disease in humans is a thriving tick
population and the expansion of suburbs into formerly wooded areas, which
increases people's exposure to infected ticks.
How can Lyme disease be prevented?
A Lyme disease vaccine is under development but is not yet available. The only
sure way to prevent the disease is to avoid exposure to infected ticks.
Especially avoid areas where wild mice might live, such as the edges of yards,
fields, and woods with low, dense groundcover.
If this is not possible, you can reduce your risk by taking these precautions:
During outside activities, wear long sleeves and long pants tucked into socks.
Wear a hat, and tie hair back.
Use insecticides to repel or kill ticks. Repellents containing the compound
DEET can be used on exposed skin except for the face, but they do not kill
ticks and are not 100% effective in discouraging ticks from biting. Products
containing permethrin kill ticks, but they cannot be used on the skin -- only
on clothing. When using any of these chemicals, follow label directions
carefully. Be especially cautious when using them on children.
After outdoor activities, check yourself for ticks, and have a "buddy" check
you, too. Check body areas where ticks are commonly found: behind the knees,
between the fingers and toes, under the arms, in and behind the ears, and on
the neck, hairline, and top of the head. Check places where clothing presses on
Remove attached ticks promptly. Removing a tick before it has been attached for
more than 24 hours greatly reduces the risk of infection. Use tweezers, and
grab as closely to the skin as possible. Do not try to remove ticks by
squeezing them, coating them with petroleum jelly, or burning them with a
Large brown ticks that are commonly found on dogs and cattle do not carry the
Lyme disease bacterium. If you remove a very small tick and want to have it
tested for Lyme disease, place it in a clean pill vial or tight-sealed plastic
storage bag with a moistened cotton swab. Contact your health-care provider and
local health department.
This fact sheet is for information only and is not meant to be used for self-
diagnosis or as a substitute for consultation with a health-care provider. If
you have any questions about the disease described above, consult a health-care