How common is Lyme disease in California? Tick-borne infections spread across US

Lyme disease is one of the most prevalent insect-borne diseases in the country, with far more cases reported each year than other diseases carried by mosquitoes, fleas and ticks, such as West Nile virus.

There were more than 62,000 reported cases of the tick-borne disease in the United States in 2022, according to the U.S. Centers for Disease Control’s data.

However, the true number of cases each year could be seven times that number due to underreporting, the CDC estimates.

The prevalence of the disease, which is spread to people through the bite of a blacklegged tick, or a deer tick, has increased dramatically since the United States first began tracking the disease in 1991.

While better surveillance explains part of the increase, the warming climate has also made more of the country suitable for the ticks that carry the disease.

See how deer ticks have spread across the United States since 1996.

Which U.S. states have the most Lyme disease cases?

As ticks have spread across the nation, so has Lyme disease.

In 2022, Vermont had one of the highest numbers of cases per capita with nearly 200 cases per 100,000 people, according to the CDC. In 1996, Vermont had only one case per 100,000 people.

The Midwest has especially increased in cases, CDC data show.

How common is Lyme disease in California?

Although Lyme disease is most common in the Northeast, mid-Atlantic, and upper Midwest regions of the United States, dozens of cases are reported each year in California, the CDC said.

According to the CDC, the prevalence of the disease in California has steadily decreased since 1991, when a total of 265 cases were reported in the state.

The number of Lyme disease cases in California has dropped sharply in recent years.

There were just 77 cases of Lyme disease in California in 2022, compared to 145 in 2017 and 144 in 2019.

What is Lyme disease?

Lyme disease is a bacterial infection that’s spread to people through the bite of blacklegged ticks, according to the CDC.

“If left untreated, infection can spread to joints, the heart and the nervous system,” the agency said.

Lyme disease is typically reported in the spring, summer and fall, but ticks can be active at any time when the temperature is above freezing.

What are the symptoms of an insect-borne disease?

Lyme disease can be identified by a red, circular skin rash that appears at the site of a tick bite three to 30 days after being bitten.

The CDC advises going to a health care provider immediately as soon as this type of rash, known as erythema migrans, is visible.

Other symptoms include: fever, headache and fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system.

When treated early, Lyme disease symptoms can go away entirely. However, if it is not treated early, the disease can be chronic, with symptoms such as arthritis, fatigue and persistent body aches.

How to prevent tick bites and avoid getting sick

The CDC advises that people wear long pants and shirts when in tick-infested areas, such as wooded areas or areas with tall grass, and to tuck pants into socks to create a barrier.

The agency advises checking sensitive areas such as armpits and behind the ears after spending time outside in one of these areas.

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