Human Diseases

Tick-Borne Diseases in Humans

Ticks can transmit many different diseases to humans. Some cause mild symptoms, while others can be serious or even life-threatening. The good news is that most tick-borne diseases can be treated successfully, especially when caught early.

For detailed information about specific diseases, see our Tick-Borne Diseases page. This page provides a quick overview of the major diseases affecting humans.

Major Tick-Borne Diseases in Humans

Lyme Disease

Lyme disease is the most common tick-borne illness in many regions, caused by the bacterium Borrelia burgdorferi.

• Primary Vector: Black-legged tick (deer tick)
• Geographic Distribution: Northeastern, mid-Atlantic, and upper midwestern United States; parts of Europe and Asia
• Early Symptoms (3-30 days after bite):
  • Fever, chills, headache, fatigue
  • Muscle and joint aches
  • Erythema migrans (EM) rash - a characteristic "bull's-eye" rash at the bite site (occurs in 70-80% of cases)
• Later Symptoms (if untreated):
  • Severe headaches and neck stiffness
  • Arthritis with severe joint pain and swelling
  • Facial palsy
  • Heart palpitations
  • Neurological problems
• Treatment: Antibiotics (doxycycline, amoxicillin, or cefuroxime)

Rocky Mountain Spotted Fever (RMSF)

RMSF is a potentially severe tick-borne disease caused by the bacterium Rickettsia rickettsii.

• Primary Vectors: American dog tick, Rocky Mountain wood tick, brown dog tick
• Geographic Distribution: Throughout the United States, particularly in the southeastern and south-central regions
• Symptoms:
  • Fever
  • Headache
  • Rash (typically appears 2-5 days after fever onset)
  • Nausea and vomiting
  • Muscle pain
  • Lack of appetite
• Treatment: Doxycycline (treatment should begin immediately when RMSF is suspected)
• Severity: Can be fatal if not treated promptly

Anaplasmosis

Anaplasmosis is caused by the bacterium Anaplasma phagocytophilum.

• Primary Vector: Black-legged tick (deer tick)
• Geographic Distribution: Similar to Lyme disease distribution
• Symptoms:
  • Fever, chills
  • Severe headache
  • Muscle aches
  • Nausea, vomiting, diarrhea
  • Loss of appetite
• Treatment: Doxycycline

Babesiosis

Babesiosis is caused by microscopic parasites (Babesia species) that infect red blood cells.

• Primary Vector: Black-legged tick
• Geographic Distribution: Primarily in the northeastern and upper midwestern United States
• Symptoms:
  • Fever, chills
  • Sweats
  • Headache
  • Body aches
  • Loss of appetite
  • Nausea
  • Fatigue
• Treatment: Combination of atovaquone and azithromycin, or clindamycin and quinine
• Note: Can be severe, especially in immunocompromised individuals

Ehrlichiosis

Ehrlichiosis is caused by bacteria in the Ehrlichia genus.

• Primary Vector: Lone star tick
• Geographic Distribution: Primarily in the southeastern and south-central United States
• Symptoms:
  • Fever, chills
  • Severe headache
  • Muscle aches
  • Nausea, vomiting, diarrhea
  • Confusion
  • Rash (more common in children)
• Treatment: Doxycycline

Powassan Virus Disease

Powassan virus disease is a rare but serious tick-borne viral illness.

• Primary Vector: Black-legged tick, groundhog tick
• Geographic Distribution: Northeastern United States and Great Lakes region
• Symptoms:
  • Fever
  • Headache
  • Vomiting
  • Weakness
  • Confusion
  • Seizures
  • Memory loss
• Treatment: Supportive care (no specific antiviral treatment)
• Severity: Can cause encephalitis and meningitis; approximately 10% of cases are fatal

Common Symptoms Across Diseases

Many tick-borne diseases share similar early symptoms, which can make diagnosis challenging:

• Fever and chills
• Headache
• Fatigue
• Muscle and joint aches
• Nausea

This is why it's important to inform healthcare providers about any recent tick exposure or bites.

Co-Infections

A single tick bite can transmit multiple diseases simultaneously. Co-infections can:

• Make diagnosis more challenging
• Result in more severe symptoms
• Require treatment for multiple pathogens
• Prolong recovery time

When to Seek Medical Attention

Seek medical attention if you experience:

• Symptoms after a known tick bite
• Fever or flu-like symptoms after spending time in tick-prone areas
• A rash, especially a "bull's-eye" or expanding rash
• Severe headache or neck stiffness
• Neurological symptoms
• Any concerns about a tick bite

Prevention

Prevention is the best defense against tick-borne diseases. See our comprehensive Tick Prevention guide for detailed strategies.

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 your physician or other qualified health provider with any questions you may have regarding a medical condition.