11 Tick-Borne Diseases You Need To Know About

Lyme disease isn't the only disease to worry about.

Close up of a tick on a leaf
Erik Karits / Pexels

Ticks are notorious for transmitting Lyme disease, but did you know these tiny arachnids can cause more than a dozen other illnesses in humans? With cases of Lyme and other tick-borne diseases on the rise from 2004 to 2016, the threat to public health is real.

"You need to put the risk of tick bites into perspective and take preventive measures," Andrea Swei, PhD, associate professor of biology at San Francisco State University, told Health. "It's important to stay informed but not panic."

Tick-Borne Diseases

Ticks are vectors, meaning they're capable of carrying and transmitting disease. You can contract a tick-borne disease through a tick bite, but not all tick-borne illnesses affect people. Only certain tick species bite and infect humans.

Likewise, different species can transmit different diseases, so patterns of illness vary widely from one region of the country to another. "You're not going to have equal risk in every location," according to Swei.

There may be as many as 300,000 to 400,000 new cases of Lyme disease in the United States (US) each year, making it the most common tick-borne illness in America. Lyme is most common in northeastern, upper midwestern, and mid-Atlantic states.

How Do Humans Get Tick-Borne Diseases?

Ticks feed on the blood of birds, reptiles, amphibians, and mammals—including people—throughout their various life stages. If a host animal has a blood-borne infection, the tick can ingest that pathogen during its blood meal. When the tick attaches to a human, that infection-causing bacterium, virus, or parasite can be passed along as the little bloodsucker engorges its body with your blood.

"Ticks are dirty, and they really do have a lot of bugs," Christine Green, MD, a family physician in Palo Alto, California, and a member of the Bay Area Lyme Foundation's scientific advisory board, told Health.

Here are several common, emerging, and rare-but-concerning tick-borne infections you should know about.


This is a bacterial infection caused by Anaplasma phagocytophilum.

This disease is found in the northeast and upper midwestern US and transmitted by the blacklegged tick (Ixodes scapularis). Meanwhile, the Western blacklegged tick (Ixodes pacificus) transmits the bug on the Pacific Coast.

"People with anaplasmosis can have high fevers; they can be pretty sick," Jennie Johnson, MD, associate medical director of Infectious Diseases and Immunology at Lifespan in Providence, Rhode Island, told Health. "They can develop a rash, but it's more like a 'diffuse rash all over the body.'"


Babesiosis is also primarily found in the northeast and upper midwestern US. It is a parasitic infection caused by Babesia microti transmitted to humans by the blacklegged tick.

"You don't really get a rash with it, except maybe at the tick bite, and it's accompanied by really severe fatigue," observed Swei, who has studied vector-borne diseases.

Borrelia Miyamotoi Disease

Borrelia miyamotoi bacteria were first identified in Japan in 1995. In the US, they are transmitted by the blacklegged and Western blacklegged ticks.

People with B. miyamotoi disease may experience fever, chills, and headache. A rash is less common, affecting fewer than 10% of patients.

Colorado Tick Fever

This rare illness caused by the Colorado tick fever virus, which is transmitted by infected Rocky Mountain wood ticks (Dermacentor andersoni).

People living in or visiting the western United States at 4,000 to 10,000 feet above sea level may be at risk of contracting the Colorado tick fever (CTF).

Common symptoms include fever, fatigue, chills, headache, and body aches.


The lone star tick (Amblyomma americanum) is responsible for transmitting diffrent species of Ehrlichia bacteria, the cause of this infection. Ehrlichiosis primarily affects people in the Southeast and south-central states.

For some people, illness can be relatively mild, while for others, it can be severe. One species of bacteria, Ehrlichia chaffeensis, can cause fatal disease if left untreated.

Lyme Disease

Lyme disease gets its name from the town in Connecticut where it was first described.

It's a bacterial infection caused by Borrelia burgdorferi and, rarely, Borrelia mayonii. Blacklegged ticks transmit the disease in the northeastern, mid-Atlantic, and north-central US, and the western blacklegged ticks spread the disease in the Pacific Coast states.

These Borrelia infections can produce a circular rash that expands over time and, in many cases, resembles a bull's eye. Fever, fatigue, muscle aches, and joint pain are just a few of the earlier symptoms of the illness.

Powassan Virus Disease

Powassan virus is rare but serious. It can cause swelling of the brain and the membranes around the brain and spinal cord.

"Not only is it fatal, but it can be transmitted very, very quickly by a biting tick," said Dr. Swei. Powassan virus can be transmitted in a matter of minutes, whereas Lyme typically takes at least 36 hours from tick bite to transmission.

Blacklegged ticks, squirrel ticks, and groundhog ticks have all been known to spread the Powassan virus.

This disease has primarily been reported in the Northeast and Great Lakes regions of the US.

Rocky Mountain Spotted Fever

As its name implies, Rocky Mountain spotted fever (RMSF) often produces a dot-like or splotchy rash. It can be fatal if left untreated.

There are other types of spotted fevers, which are caused by a type of bacteria called Rickettsia. The most common and serious of the spotted fevers is RMSF. RMSF is caused by the bacteria Rickettsia rickettsii.

It can be transmitted by the American dog tick (Dermacentor variabilis) in the Eastern, Central, and Western US; the Rocky Mountain wood tick in the Rocky Mountain states; and the Brown dog tick (Rhipicephalus sanguineus) at the US-Mexican border.

Dr. Swei said, "Rocky Mountain spotted fever has recently appeared in impoverished areas of the Southwest where ticks can enter and live in people's homes."

Southern Tick-Associated Rash Illness (STARI)

STARI can produce a red, bulls-eye rash and other Lyme-like symptoms.

But the vector is different. STARI is transmitted by the lone star tick, which live from Central Texas and Oklahoma eastward through southern states and along the Atlantic coast, all the way up to Maine.

The cause remains unknown. "We know it's not caused by Borrelia burgdorferi, the pathogen responsible for most cases of Lyme," John Aucott, MD, Director of the Johns Hopkins Lyme Disease Clinical Research Center in Baltimore, told Health.

Tick-Borne Relapsing Fever (TBRF)

Soft ticks of the genus Ornithodoros transmit certain Borrelia bacteria that cause TBRF. The illness, which triggers a high and often recurring fever, is found primarily in the Western states.

About 20 cases of TBRF are reported each year in the US, so TBRF is pretty rare.


There are a number of ways humans can contract tularemia, a bacterial infection caused by Francisella tularensis. Bites by a dog tick, wood tick, or lone star tick can put you at risk, as can handling sick or dead animals with the infection.

Although cases of tularemia have been reported in all states aside from Hawaii, cases are most common in south-central states, the Pacific Northwest, and parts of Massachusetts.

Symptoms depend on how the infection enters a person's body. You might develop a skin ulcer, fever, or swollen glands.

A Quick Review

Everyone knows that we have to be wary of Lyme disease, but it turns out that ticks can cause a number of other illnesses, too. These illnesses can be mild for some but severe or even fatal for others. Consider this another reason to protect yourself from tick bites.

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