Lyme disease can cause symptoms that overlap with many other health conditions. Here’s why that can make it difficult to recognize — and why the details surrounding a possible tick exposure matter.
Fatigue. A headache. Muscle aches. Joint pain. Fever.
Those symptoms could point to a lot of different things, which is one reason Lyme disease can be difficult to recognize at first.
The CDC says untreated Lyme disease can cause a wide range of symptoms depending on the stage of infection. Early symptoms can include fever, chills, headache, fatigue, muscle and joint aches, and swollen lymph nodes. Later symptoms can involve the nervous system, heart and joints.
And the symptoms are only part of the picture. Someone may not even notice that they were bitten by a tick, and the well-known bullseye rash does not appear in every case. Mayo Clinic notes that many people will not notice they’ve had a tick bite, while the CDC says an erythema migrans rash occurs in about 70% to 80% of infected people.
That combination can make Lyme disease look less obvious than people expect.
Why Is Lyme Disease Called “The Great Imitator”?
Lyme disease has been called “the great imitator” because its symptoms can overlap with those of other illnesses.
The U.S. Department of Health and Human Services uses that phrase to describe Lyme disease, explaining that the disease can affect nearly every body system and produce wide-ranging symptoms that overlap with other infections and autoimmune conditions.
That means Lyme disease does not always present with one easy-to-recognize set of symptoms.
Symptoms can also vary depending on the stage of infection. Early Lyme disease can look different from Lyme disease that has spread to other areas of the body.
If you want a closer look at how those stages differ, read The Stages of Lyme Disease: What Changes Over Time.
In other words, there isn’t one symptom that always makes Lyme disease immediately obvious.
What Lyme Disease Symptoms Can Look Like Other Conditions?
Some of the earliest Lyme disease symptoms are also symptoms people experience with many other illnesses.
The CDC lists early symptoms such as:
- Fever
- Chills
- Headache
- Fatigue
- Muscle and joint aches
- Swollen lymph nodes
These symptoms may occur even without a rash.
Johns Hopkins also notes that early Lyme symptoms including fever, severe fatigue and body aches can resemble other common illnesses, which can make early diagnosis challenging.
As Lyme disease progresses, the possible symptoms can become even broader.
The CDC lists later symptoms including facial palsy, nerve pain, numbness or tingling, irregular heartbeat, arthritis with joint pain and swelling, and inflammation of the brain and spinal cord.
That wide range is part of why Lyme can look different from one person to another.
Why Can Lyme Disease Be Difficult to Recognize?
There isn’t just one reason. Several pieces can make the picture less clear.
You May Not Remember a Tick Bite
A tick bite can be easy to miss.
Harvard Health notes that not everyone who develops Lyme disease symptoms remembers being bitten because deer ticks are very small and their bites can go unnoticed.
So someone may begin feeling sick without immediately connecting those symptoms to a possible tick exposure.
Not Everyone Gets the Classic Bullseye Rash
The bullseye rash may be one of the most recognizable images associated with Lyme disease, but it is not something everyone experiences.
The CDC says an erythema migrans rash occurs in approximately 70% to 80% of infected people. It also explains that the rash can take several forms and does not always look like a classic bullseye.
Mayo Clinic also notes that a rash is common but does not always occur.
We’ll take a closer look at the different ways Lyme rashes can appear in The Bullseye Rash Myth: What Lyme Actually Looks Like on Skin.
Symptoms Can Change Over Time
Lyme disease does not necessarily look the same throughout an infection.
Early Lyme may involve fever, fatigue, headache and muscle or joint aches. Later Lyme can involve neurological symptoms, heart-related problems or arthritis.
That changing pattern is another reason understanding the stages of Lyme disease can be helpful.
The Symptoms Aren’t Unique to Lyme Disease
Perhaps the clearest explanation for the “great imitator” nickname is that many Lyme symptoms can also occur with other health conditions.
The CDC specifically tells healthcare providers to consider the possibility that other illnesses may cause similar symptoms when evaluating someone for Lyme disease.
That does not mean every unexplained symptom could be Lyme. It means symptoms need context.
What Information Can Help Give Symptoms More Context?
If Lyme disease symptoms can overlap with other conditions, details about possible exposure become especially useful.
When evaluating someone for Lyme disease, the CDC says healthcare providers consider the person’s signs and symptoms, the likelihood of exposure to infected blacklegged ticks, the possibility that other illnesses could cause similar symptoms and laboratory test results when indicated.
That means it can be helpful to keep track of things like:
- Recent outdoor activity
- Where you were
- Whether you found an attached tick
- Approximately when the bite or possible exposure occurred
- Where the tick was attached
- Any rash or other skin changes
- When symptoms began
- How symptoms have changed
You do not need to figure out what those details mean on your own. The point is to have useful information available if you speak with a healthcare provider.
If you have recently found a tick, our I Found a Tick. Now What? guide walks through what to do next.
Can Lyme Disease Be Diagnosed From Symptoms Alone?
Not necessarily.
The CDC says healthcare providers consider multiple factors when evaluating someone for Lyme disease, including signs and symptoms, possible exposure to infected ticks, whether another illness could cause similar symptoms and laboratory testing when appropriate.
Blood testing also has limitations, especially early in an infection. Lyme blood tests look for antibodies, and the CDC explains that it can take several weeks for the immune system to produce enough antibodies to be detected. Tests may therefore be falsely negative during the first few weeks of infection.
Johns Hopkins makes a similar point, explaining that antibody-based blood tests may be negative during the first few weeks because the body has not yet produced detectable levels of antibodies.
This is another reason diagnosis involves more than looking at one symptom or one piece of information.
Why Does Recognizing Possible Lyme Exposure Matter?
Knowing that you may have been exposed to ticks gives symptoms important context.
The CDC recommends seeking medical attention if you develop Lyme disease signs or symptoms after a recent tick bite, or after living in or traveling to an area where Lyme disease is common.
The CDC also emphasizes that early diagnosis and proper treatment can help prevent later Lyme disease.
This does not mean you need to assume Lyme disease every time you feel tired or achy after being outside. It means that remembering possible tick exposure — and sharing that information with a healthcare provider — can add another piece to the puzzle.
The Bigger Takeaway
Calling Lyme disease “the great imitator” does not mean every unexplained headache, fever or sore joint is Lyme disease.
It means Lyme can affect multiple areas of the body and cause symptoms that overlap with other illnesses. HHS notes that Lyme symptoms can overlap with other infections and autoimmune conditions, while the CDC says healthcare providers should consider whether other illnesses could explain similar symptoms.
Knowing whether you’ve had possible tick exposure, paying attention to changes and keeping track of useful details can help give those symptoms more context.
The goal isn’t to assume the worst after every hike, backyard afternoon or tick encounter. It’s to know what information matters if something doesn’t feel right.
Frequently Asked Questions
Why is Lyme disease called “the great imitator”?
Lyme disease has been called “the great imitator” because it can affect multiple body systems and cause symptoms that overlap with other illnesses. HHS specifically notes that Lyme can produce wide-ranging symptoms that overlap with other infections and autoimmune conditions.
What illnesses can Lyme disease look like?
Rather than pointing to one specific illness, HHS says Lyme symptoms can overlap with other infections and autoimmune conditions. The CDC also notes that healthcare providers consider whether another illness could be responsible for similar symptoms when evaluating someone for Lyme disease.
Can you have Lyme disease without a bullseye rash?
Yes. The CDC says an erythema migrans rash occurs in about 70% to 80% of infected people, meaning not everyone develops one. The rash can also take several forms and does not always have the stereotypical bullseye appearance.
Can you have Lyme disease without remembering a tick bite?
Yes. Harvard Health notes that not everyone who develops Lyme disease symptoms remembers being bitten because deer ticks are very small and their bites can go unnoticed.
How do doctors determine if someone may have Lyme disease?
According to the CDC, healthcare providers consider symptoms, the likelihood of exposure to infected blacklegged ticks, whether another illness may be causing similar symptoms and laboratory test results when indicated. Blood tests detect antibodies, which can take several weeks to reach detectable levels after infection.
Sources and Further Reading
- CDC — Signs and Symptoms of Untreated Lyme Disease
- CDC — Testing and Diagnosis for Lyme Disease
- CDC — Clinical Testing and Diagnosis for Lyme Disease
- HHS — Lyme Disease
- Johns Hopkins — Diagnosis of Lyme Disease
- Harvard Health — Lyme Disease A to Z
This article is for general educational purposes and is not a substitute for medical advice.
