Babesiosis
Also called: Babesia
Pathogen
Babesia microti (East/Midwest); Babesia duncani (West)
Carried by
Blacklegged / deer tick (Ixodes scapularis)
Babesia is a malaria-like parasite that infects red blood cells. Because it's a parasite rather than a bacterium, it does not respond to the antibiotics used for Lyme — which is exactly why it's so often missed in people who were treated for Lyme but never got fully better. It's transmitted by the same blacklegged tick that carries Lyme, and can also spread through blood transfusion.
Night sweats and air hunger are the classic red flags. If those describe you and Lyme treatment alone hasn't worked, ask specifically about Babesia.
Symptoms
- Drenching night sweats and unexplained chills
- "Air hunger" — feeling short of breath with normal lungs
- Severe fatigue and deep exhaustion
- Headaches, especially behind the eyes
- Hemolytic anemia in more serious cases
- Symptoms that cycle or feel wave-like
Testing
A blood smear can reveal the parasites inside red blood cells (the classic 'Maltese cross' form), and PCR detects Babesia DNA; antibody testing is supportive. Because parasite levels fluctuate, testing during symptomatic periods improves the odds of catching it.
Labs often used in the Lyme community:
See our Testing Guide to understand your options.
Geography
Highest incidence is in the Northeast and Upper Midwest — Rhode Island, Maine, Massachusetts, Connecticut, and New York report the most cases. Babesia duncani appears in Western states. Cases have been rising and expanding geographically.
Explore the Where Ticks Live map to see what's carried in your region.
Treatment overview
Because it's a parasite, Babesiosis is treated with anti-parasitic medication — most commonly atovaquone combined with azithromycin, typically for 7–10 days, with longer or combination therapy for persistent cases. Severe disease may require additional agents. Treatment is very different from Lyme antibiotics.
Frequently asked questions
Why didn't my Lyme antibiotics treat Babesia?
Babesia is a parasite, not a bacterium, so the antibiotics used for Lyme have no effect on it. It requires anti-parasitic medication — a common reason people improve only partially on Lyme treatment.
What is 'air hunger'?
It's the sensation of not being able to get a full, satisfying breath even though your lungs are working normally. It's one of the most characteristic Babesia symptoms.