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You may have heard of Lyme disease, but what about Rocky Mountain spotted fever (RMSF), babesiosis, ehrlichiosis, or anaplasmosis? Aside from Lyme disease, the Centers for Disease Control and Prevention (CDC) tracks more than a dozen tickborne illnesses. Fortunately, these are much rarer than Lyme disease.

Tickborne illnesses are on the rise due to climate change. Warmer weather means ticks may bite over a longer period throughout the year and thrive in larger geographic areas.

Ticks usually transmit disease in the spring, summer, or fall. But they can also pass on disease-causing bacteria in the winter in areas with consistently above-freezing temperatures.

Most tickborne illnesses won’t cause long-term problems if your doctor diagnoses and treats them early. That’s why it’s a good idea to check yourself for ticks after you spend time in forested or grassy areas.

You can prevent all tickborne illnesses in the same way — by avoiding tick bites.

Are you worried you or someone you know could have a tickborne illness? Here are some key facts about the five most common tickborne illnesses in the U.S.

Lyme Disease

Lyme disease is the most common tickborne illness. It accounts for almost 70% of all illnesses caused by ticks and mosquitos in the U.S., according to the CDC.

There were 63,000 cases in the U.S. in 2022 (the most recent year with available data). But the CDC estimates the real number is closer to 475,000 cases a year because many cases go undetected.

The disease most commonly spreads from ticks found in the northeastern states. Parts of the Midwest and along the Pacific coast also have a high prevalence of Lyme disease-carrying ticks.

A blacklegged (deer) tick or western blacklegged tick needs to become fully engorged before the Lyme disease-causing bacteria can move from the gut to the saliva glands. This process usually takes 36 hours or more. So Lyme disease is very unlikely if you carefully remove a tick within hours of its attachment.

Symptoms of Lyme disease

Symptoms of Lyme disease most commonly appear within a week or two of the tick bite. They include:

• A “bullseye” rash at the location of the bite within three to 30 days of the tick bite.
• Fever and chills.
• Headache.
• Muscle and joint aches.

If Lyme disease spreads beyond the initial region of the bite (which can take many weeks to months), it can cause:

• Dizziness.
• Facial palsy (weakness in the facial muscles on one side).
• Nerve pain.
• Severe headache.
• Severe joint pain and swelling.
• Shortness of breath.
• A stiff neck.

Anaplasmosis

This is the second-most-common tickborne illness after Lyme disease. Based on CDC data from the four most recent years with data available, there are about 5,400 cases in the U.S. each year. It most commonly occurs in the upper Midwestern and northeastern parts of the U.S.

The same blacklegged ticks and western blacklegged ticks that carry the Lyme-disease-causing bacteria can carry the anaplasmosis-causing bacteria.

Symptoms of anaplasmosis

Symptoms of anaplasmosis often occur within five days of the tick bite. They include:

• Diarrhea.
• Fever and chills.
• Headache.
• Loss of appetite.
• Muscle aches.
• Nausea.
• Vomiting.

People who are older or have a compromised immune system (due to cancer, medication, HIV, or another reason) can get very sick from anaplasmosis. In rare cases, the disease can cause organ failure and death.

Babesiosis

The parasite Babesia can spread from blacklegged ticks, which are mostly found in the Northeast and upper Midwest. The tickborne illness is rare, with cases ranging from around 1,500 to 2,500 per year.

Young ticks, not adult ticks, spread the Babesia parasite, making it different from other tickborne diseases. Because the nymphs are only the size of a poppy seed, people who get babesiosis may not recall getting a tick bite.

Symptoms of Babesiosis

After the Babesia parasite enters the blood, symptoms can take one to six weeks to develop. Some people don’t get any symptoms from babesiosis because their immune system fights the disease. Many people only get mild symptoms that don’t require hospital care, including:

• Body aches.
• Fatigue.
• Fever and chills.
• Headache.
• Loss of appetite.
• Nausea.

People who are older or have a compromised immune system are at risk of severe babesiosis. This can include yellowing of the skin and eyes, severe vomiting, neck stiffness, mood changes, and shortness of breath.

Rocky Mountain Spotted Fever

Though rare, Rocky Mountain spotted fever is a serious illness. If not promptly treated, it can cause death. There are around 1,200 cases of RMSF in the U.S. each year.

Ticks throughout the U.S. can carry Rocky Mountain Spotted Fever, but reports of the disease are most common in North Carolina, Tennessee, Missouri, Arkansas, and Oklahoma. That’s according to the CDC. Unlike Lyme disease, adult ticks can spread the bacteria that causes it even if they’re attached for a short time.

Symptoms of Rocky Mountain spotted fever

Symptoms can appear three to 12 days after a tick bite. They include:

• A rash (small, flat, red or pink splotches that usually start on the wrists and ankles and spread to the rest of the body).
• Fever.
• Confusion.
• Headache.
• Joint and muscle pain.
• Lack of Appetite.
• Stomach pain.

Ehrlichiosis

Some call ehrlichiosis spotless Rocky Mountain spotted fever because the symptoms are similar and serious. However, ehrlichiosis is less likely to cause a rash.

The CDC reports about 1,500 cases of ehrlichiosis per year. It most often appears in ticks in central and eastern states, especially New York, Missouri, Arkansas, North Carolina, and Tennessee.

Symptoms of ehrlichiosis

Ehrlichiosis symptoms usually occur a week or two after the tick bite. They include:

• A rash that looks like red splotches or dots. Rashes occur in about one-third of people who have ehrlichiosis.
• Fever.
• Confusion.
• Headache.
• Muscle aches.
• Nausea and vomiting.
• Stomach pain.

What to Do if You Think You Have a Tickborne Illness

In most cases, doctors will only order tests or prescribe treatments for tickborne illnesses if you have symptoms.

However, your doctor may treat you for Lyme disease (even if you don’t have symptoms) if you meet all the following criteria:

• You found an attached blacklegged tick on your body in an area where Lyme is prevalent. (The CDC’s website has maps that show Lyme disease prevalence).
• You discovered the tick within the past 72 hours.
• The adult tick may have attached itself to the skin for 36 hours or longer.

See a doctor if you develop a fever or other unexplained symptoms days or weeks after noticing a tick or spending time in a wooded or grassy area. They’ll ask about your symptoms, examine you, and consider which tests to order to diagnose your illness. If a tickborne illness is possible, they can test you for those that can occur in your area.