How soon do symptoms start after a tick bite?

It depends on the infection. For example, CDC notes early Lyme signs and symptoms can occur 3–30 days after a tick bite, while RMSF signs and symptoms can begin 3–12 days after a tick bite. See the symptom timeline table on this page and the linked CDC sources.

When can a Lyme blood test be falsely negative?

CDC notes that antibody tests may appear falsely negative during the first few weeks of infection, typically when a patient has an erythema migrans rash, and that FDA-cleared assays have good sensitivity after 4–6 weeks have passed.

What is STARI, and how is it related to Lyme disease?

CDC notes that a red, expanding rash similar to erythema migrans can occur with Southern Tick-associated Rash Illness (STARI), which is associated with lone star tick bites and is not Lyme disease.

Why do clinicians treat RMSF before test results return?

CDC notes that some blood test results for RMSF can take weeks and that if a healthcare provider thinks an illness might be RMSF, they should recommend antibiotic treatment before test results are available.

Human Diseases - Tick-Borne Illnesses

Q: Is a small red bump right after a tick bite a sign of Lyme disease?

Not usually. CDC notes that a small bump or redness immediately after a tick bite that resembles a mosquito bite is common and generally goes away in 1–2 days and is not a sign of Lyme disease.

Q: When should I ask about babesiosis or anaplasmosis (co-infection)?

Co-infections can occur because some ticks carry more than one pathogen. If you have ongoing fever or worsening symptoms after a tick bite or suspected Lyme disease—especially with drenching sweats or signs of anemia (e.g., jaundice or dark urine)—ask a clinician about other tick-borne infections such as babesiosis or anaplasmosis.

Last updated: January 24, 2026

What changed in this update:

Added clearer symptom differential modules (Lyme vs STARI, RMSF urgency, and co-infection suspicion signals).
Updated citations and refreshed the “Cite this section” sources list.

Tick-borne diseases in humans (quick, evidence-first overview)

Tick-borne illness often starts with “flu-like” symptoms (fever, headache, fatigue) that overlap across conditions. Because some diseases can progress quickly, the most useful approach is to pair symptoms with timing after exposure and red-flag severity signs, then seek care promptly.

Key takeaways

Timing matters: different diseases tend to begin symptoms on different timelines after tick exposure.
Rash isn’t always diagnostic: some rashes look similar (e.g., EM vs STARI) and some diseases may have variable rash.
Testing has timing limits: CDC notes early Lyme antibody tests can be falsely negative and improve after 4–6 weeks.
Don’t delay urgent care: severe headache, confusion, neck stiffness, or neurologic symptoms after tick exposure warrant urgent evaluation.

Cite this section

All About Ticks. Human Diseases - Tick-Borne Illnesses. Updated 2026-01-24. Sources: CDC Lyme signs/symptoms and diagnosis/testing; CDC STARI overview; CDC RMSF signs/symptoms (HCP) and RMSF overview; CDC anaplasmosis clinical signs (HCP); CDC ehrlichiosis, babesiosis, and Powassan symptom pages.

Primary sources: CDC - Lyme signs & symptoms, CDC - Lyme diagnosis & testing, CDC - About STARI, CDC - RMSF signs & symptoms (HCP)

Act fast if you’re sick after tick exposure

If you develop fever/headache after tick exposure—especially with a new rash, confusion, severe headache, neck stiffness, or neurologic symptoms—seek medical care urgently. For suspected RMSF, CDC notes treatment should begin before test results are available.

Primary sources used below: CDC Lyme signs/symptoms and testing guidance; CDC RMSF signs/symptoms (HCP); CDC anaplasmosis clinical signs (HCP); CDC ehrlichiosis signs/symptoms; CDC babesiosis signs/symptoms; CDC Powassan symptoms/diagnosis/treatment.

Symptom timeline (incubation window) by disease

These are typical onset windows reported by CDC. Individual timelines vary.

Disease	Typical symptom onset after tick bite/infection	High-signal notes	Primary source
Lyme disease	Early signs and symptoms: 3–30 days after tick bite	EM rash begins after a delay; appearance can vary and is not always a classic “bull’s-eye”	CDC — Lyme signs & symptoms
Rocky Mountain spotted fever (RMSF)	3–12 days after tick bite	Rapidly progressive; without early doxycycline can be fatal within days	CDC — RMSF signs & symptoms (HCP)
Anaplasmosis	5–14 days after tick bite	Many people do not remember being bitten	CDC — Anaplasmosis clinical signs (HCP)
Ehrlichiosis	1–2 weeks after tick bite	Rash reported by up to 1 in 3; rash is more common in children	CDC — Ehrlichiosis signs & symptoms
Babesiosis	Can start about a week after infection; usually develops over weeks to months (or longer)	Many people have no symptoms; can be severe in certain risk groups	CDC — Babesiosis signs & symptoms
Powassan virus	1 week to 1 month from tick bite to feeling sick	Can cause severe neurologic disease (encephalitis/meningitis)	CDC — Powassan symptoms/diagnosis/treatment

Rash & “is this Lyme?” differentials (high-yield)

Rashes after tick bites can be confusing. These sections are designed to help you describe what you’re seeing to a clinician and avoid false reassurance.

Lyme vs STARI (rash look-alikes)

CDC notes that STARI can cause a red, expanding rash that looks very similar to erythema migrans (EM), but STARI is not Lyme disease and is associated with lone star tick bites.

Feature	Lyme disease (EM rash)	STARI
Timing	Early signs/symptoms typically 3–30 days after a tick bite (CDC)	Rash can appear within about 7 days after a tick bite (CDC)
Rash appearance	Can expand; can vary; not always a classic “bull’s-eye” (CDC)	Red, expanding lesion; can sometimes develop a target/bull’s-eye look (CDC)
Associated tick	Spread by blacklegged ticks (CDC)	Associated with lone star tick bites (CDC)
Key point	Lyme disease is caused by Borrelia bacteria (CDC)	CDC notes the cause of STARI is unknown; there’s no diagnostic blood test specifically for STARI

Sources: CDC — Lyme signs & symptoms, CDC — About STARI.

RMSF urgency (don’t wait if you’re sick)

Why this matters: CDC describes RMSF as rapidly progressive; if RMSF is suspected, antibiotic treatment should begin before test results are available.

Don’t rely on rash: CDC notes RMSF rash can be variable and may be absent early.
Timing signal: symptoms can begin within days (CDC: typically 3–12 days after bite).
Action signal: fever/headache after tick exposure + worsening illness warrants urgent evaluation.

Sources: CDC — RMSF signs & symptoms (HCP), CDC — About RMSF.

Quick sanity checks (bite irritation vs expanding rash)

Immediate bite irritation: CDC notes a small bump/redness immediately after a tick bite that resembles a mosquito bite is common, usually goes away in 1–2 days, and is not a sign of Lyme disease.
Expanding rash days later: consider EM/STARI look-alikes and use the official sources linked above.

Testing & timing (why early tests can mislead)

Lyme disease blood tests

CDC notes that antibody tests may be falsely negative during the first few weeks of infection (often when EM rash is present), and that FDA-cleared assays have good sensitivity after 4–6 weeks have passed.

Source: CDC — Lyme diagnosis & testing

RMSF: don’t wait for test results

CDC notes that some RMSF blood test results can take weeks, and that if RMSF is suspected, antibiotic treatment should begin before results are available.

Source: CDC — About RMSF

Major tick-borne diseases (what to look for)

Lyme disease

Typical onset: 3–30 days after tick bite (CDC)
Early symptoms: Fever, chills, headache, fatigue, muscle/joint aches; EM rash may occur and can vary in appearance
Later symptoms (untreated): Arthritis, facial palsy, neurologic and cardiac manifestations can occur (CDC)
Testing timing: Early antibody tests can be falsely negative; sensitivity improves after 4–6 weeks (CDC)

Sources: CDC — Lyme signs & symptoms, CDC — Lyme diagnosis & testing

Rocky Mountain spotted fever (RMSF)

Typical onset: 3–12 days after tick bite (CDC)
Pattern: Sudden fever/headache; rash often appears 2–4 days after fever onset and can be variable (CDC)
Why urgent: CDC notes RMSF is rapidly progressive and without early doxycycline can be fatal within days
Testing timing: CDC notes results can take weeks; suspected RMSF should be treated before results are available

Sources: CDC — RMSF signs & symptoms (HCP), CDC — About RMSF

Anaplasmosis

Typical onset: 5–14 days after tick bite (CDC)
Common symptoms: Fever, headache, muscle aches; many people do not remember a tick bite (CDC)

Source: CDC — Anaplasmosis clinical signs (HCP)

Ehrlichiosis

Typical onset: 1–2 weeks after tick bite (CDC)
Rash: CDC notes up to 1 in 3 report a rash; rash is more common in children and can appear about 5 days after fever begins

Source: CDC — Ehrlichiosis signs & symptoms

Babesiosis

Typical onset: Symptoms can start about a week after infection, but usually take weeks to months to develop (or longer) (CDC)
Note: Many people have no symptoms (CDC)

Source: CDC — Babesiosis signs & symptoms

Powassan virus disease

Typical onset: 1 week to 1 month from tick bite to feeling sick (CDC)
Severity: Can cause severe disease including encephalitis or meningitis (CDC)
Treatment: Supportive care (no specific antiviral treatment) (CDC)

Source: CDC — Powassan symptoms/diagnosis/treatment

Co-infections (one bite, more than one pathogen)

Co-infections can occur because some ticks can carry more than one pathogen. CDC notes that anaplasmosis has been reported in up to 10% of patients with Lyme disease, and that other co-infections can occur less frequently.

Co-infection “signals” to mention to a clinician

These are not diagnostic, but they can help a clinician decide what to test for (especially in endemic regions).

Babesiosis (possible signals)

Fever, chills, and sweats
Fatigue that feels out of proportion
Signs of hemolytic anemia such as jaundice or dark urine (CDC)

Source: CDC — Babesiosis signs & symptoms

Anaplasmosis (possible signals)

Fever/chills + headache + muscle aches
Worsening illness after tick exposure even without a remembered bite (CDC)

Source: CDC — Anaplasmosis clinical signs (HCP)

Higher-risk situations: CDC notes babesiosis can be severe in certain groups (e.g., people without a spleen, older adults, or immunocompromised). If you’re in a higher-risk group and feel ill after a tick bite, seek care promptly.

Sources: CDC — Lyme diagnosis & testing, CDC — Babesiosis signs & symptoms, CDC — Anaplasmosis clinical signs (HCP).

When to seek medical attention

Urgent: Fever with severe headache, confusion, neck stiffness, seizures, or new neurologic symptoms after tick exposure
Also important: Fever/flu-like illness after tick exposure (even if you don’t remember a bite)
Rash: Any expanding rash days after a bite, or a new rash paired with fever

What to do next

Remove ticks promptly: See Tick Removal
Prevent future bites: See Tick Prevention
Track timing: Write down exposure date(s), symptom start date, and take photos of any rash progression

FAQ (fast answers)

It depends on the infection. CDC notes early Lyme signs and symptoms can occur 3–30 days after a tick bite, and RMSF signs and symptoms can begin 3–12 days after a tick bite. See the symptom timeline table above for more examples.

CDC notes a small bump or redness immediately after a tick bite that resembles a mosquito bite is common, generally goes away in 1–2 days, and is not a sign of Lyme disease. (CDC source)

CDC notes antibody tests may be falsely negative during the first few weeks of infection (often when EM rash is present), and that FDA-cleared assays have good sensitivity after 4–6 weeks have passed. (CDC source)

CDC notes STARI can cause a red, expanding rash similar to erythema migrans and is associated with lone star tick bites, but STARI is not Lyme disease. (CDC source)

CDC notes some RMSF blood test results can take weeks and that if RMSF is suspected, antibiotic treatment should be started before results are available. (CDC source)

Co-infections can occur. If you have ongoing fever or worsening symptoms after a tick bite or suspected Lyme disease—especially with drenching sweats or signs of anemia (like jaundice or dark urine)—ask a clinician about other tick-borne infections such as babesiosis or anaplasmosis. (CDC babesiosis source)

Important note

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition.

Human Diseases