Ehrlichiosis is an illness you get from a tick bite. It’s caused by the bacteria Ehrlichia. Symptoms include fever, muscle aches and headache. Only about 30% of people (usually children) get a rash. Ehrlichiosis can cause serious complications if not treated quickly with antibiotics. Ehrlichiosis is found in many parts of the U.S.
Ehrlichiosis (“err-lik-ee-OH-sis”) is an illness caused by the bacteria Ehrlichia chaffeensis, E. ewingii or E. muris eauclairensis. You can get ehrlichiosis through the bite of infected ticks, including the lone star tick and the blacklegged tick.
Symptoms can start out mild and flu-like, but if not treated quickly, ehrlichiosis can be life-threatening. Ehrlichiosis is sometimes called human monocytic ehrlichiosis (HME).
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You get both ehrlichiosis and Lyme disease from tick bites, but they can cause different symptoms. Ehrlichiosis can cause life-threatening illness if not treated right away.
An infection with Ehrlichia bacteria can be serious if not treated. Nearly 60% of people with ehrlichiosis are hospitalized. It’s estimated that 1% of cases are fatal.
Ehrlichiosis can affect anyone who’s bitten by a tick. Ticks usually live in tall grass and in wooded areas. Your pets can also carry them.
While anyone can get ehrlichiosis, there are more reported cases in people assigned male at birth. You’re at higher risk for getting severely ill with ehrlichiosis if you’re:
In the U.S., ehrlichiosis is found mostly in the Midwest, South Central and Eastern regions. It’s also found in other areas around the world.
While ehrlichiosis is still pretty uncommon, cases have gone up from 200 cases per year in 2000 to over 2,000 cases in 2019. You’re more likely to get ehrlichiosis in the early summer months (May to July) or in September. Ticks are common during the summer when people are outdoors a lot.
Ehrlichia, the bacteria that cause ehrlichiosis, gets into your bloodstream from the bite of a tick. It infects and eventually destroys your white blood cells, an important part of your immune system.
Symptoms of ehrlichiosis start five to 14 days after you’re bitten. They usually start suddenly with flu-like symptoms and progress to additional symptoms. Rash from ehrlichiosis is more common in children than adults.
Symptoms of ehrlichiosis include:
A few days later, you may get additional symptoms:
Three types of Ehrlichia bacteria cause ehrlichiosis: E. chaffeensis, E. ewingii and E. muris eauclairensis. Symptoms of all three are similar, but E. chaffeensis is most likely to cause serious illness. You get infected with Ehrlichia when a tick bites an infected animal and then bites you.
Ehrlichiosis is spread from animals to humans through tick bites. The most common carriers are the lone star tick and the blacklegged (deer) tick. Ticks bite infected animals, like deer, dogs or coyotes, and then bite you. This spreads the bacteria to your body.
In rare cases, you can get ehrlichiosis from a blood transfusion or organ transplant.
No, ehrlichiosis doesn’t spread directly from person to person (it’s not contagious).
To diagnose ehrlichiosis, your healthcare provider will give you a physical exam and ask you about your symptoms and health history. It’s important for them to know if you’ve recently (within the past three weeks) been in an area where you could’ve been bitten by a tick, even if you don’t remember being bitten. They’ll use this information and blood tests to decide whether you should be treated for ehrlichiosis.
Blood tests can be used to confirm a diagnosis of ehrlichiosis. Your provider will take a sample of your blood from your arm with a small needle. A lab will do a blood count on your sample and look for signs of bacteria that cause ehrlichiosis. They’ll try to get bacteria to grow.
Growing bacteria can take several weeks, so your provider will probably have to decide whether to treat you for ehrlichiosis before the results are back. They can use blood counts (which come back quickly) to know whether you might have an infection.
Ehrlichiosis is treated with antibiotics. You usually have to take antibiotics until at least three days after your fever goes away and your symptoms improve. That’s usually about five to seven days.
Treatment is most effective when started soon after your symptoms appear. If it’s started too late, ehrlichiosis can cause serious complications that put you in the hospital.
Ask your provider if it’s safe to treat your symptoms at home. If your symptoms are mild, they may recommend over-the-counter drugs to manage them.
If you start antibiotics soon after the symptoms of ehrlichiosis appear, you should feel better within 24 to 48 hours. Continue taking antibiotics for as long as your provider prescribes, even after you feel better. If you don’t start feeling better within a few days, contact your healthcare provider.
Avoiding tick bites is the best way to reduce your risk of ehrlichiosis.
Most people make a full recovery from ehrlichiosis if treated quickly after symptoms start. Depending on how sick you are, you may need to be treated in the hospital.
If not treated quickly enough, some people with ehrlichiosis have serious or life-threatening complications, including:
The outlook for ehrlichiosis is good if treated quickly. People who start antibiotics soon after their symptoms appear usually don’t have serious complications.
Ehrlichiosis can go away with treatment, but it can take a few weeks after finishing antibiotics to feel better completely.
Ehrlichiosis can be fatal if you have serious complications. The fatality (death) rate for ehrlichiosis is 1%.
Make sure you take all of your medicine for ehrlichiosis as prescribed. If you stop taking antibiotics too soon, you may get sick again.
Ask your provider about managing your symptoms at home. Call them right away if you have new or worsening symptoms.
If you’ve been bitten by a tick or have been in an area with ticks and have symptoms of ehrlichiosis, see your healthcare provider right away.
Keep an eye out for any symptoms if you get bitten by a tick. You don’t need to see your provider if you don’t have symptoms yet. Taking antibiotics when you’re not sick won’t help prevent ehrlichiosis.
Go to the nearest ER if you have any of these symptoms:
Ehrlichiosis can be serious in dogs if not treated. It can become an ongoing (chronic) illness that can be fatal. See your veterinarian if you have questions about ehrlichiosis and your pet.
A note from Cleveland Clinic
Ticks not only bug you, they can also spread serious illnesses. While uncommon, cases of ehrlichiosis have been going up in the U.S. If you’re often in areas that have ticks, know how to prevent bites and safely remove ticks you find on yourself.
If you do get bitten, be on the lookout for illnesses caused by ticks. If you develop symptoms of ehrlichiosis or any other tick-borne disease, contact your provider right away. You can recover quickly with early treatment.
Last reviewed by a Cleveland Clinic medical professional on 08/16/2022.
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