Babesia Cases Surge in New York as Babesiosis Spreads
Babesia infections are increasing across New York and the Northeast.
A Hudson Valley study found one of the sharpest rises in reported cases.
Current surveillance confirms that babesiosis remains a growing concern.
Babesia cases in New York are increasing, particularly in the Hudson Valley and other endemic regions. Researchers studying the Hudson Valley documented one of the most dramatic increases in reported cases, providing an example of how babesiosis is expanding across the Northeast.
In their article Increasing incidence and changing epidemiology of babesiosis in the Hudson Valley region of New York State: 2009-2016, Joseph and colleagues examined how Babesia infections were spreading even though animal reservoirs such as mice, shrews, and voles typically do not travel long distances.[1]
Babesiosis is a tick-borne parasitic infection that can cause fever, chills, fatigue, night sweats, anemia, and shortness of breath. Cases have increased in several regions of the United States, particularly in the Northeast, making early recognition increasingly important.
Read More: Babesia remains a clinical diagnosis for some patients.
New York Reports Growing Numbers of Babesia Infections
Babesiosis became a nationally notifiable disease in 2011. Between 2011 and 2016, New York State reported 2,750 Babesia cases, the highest number reported by any state during that period.[1]
A subsequent CDC analysis found that New York reported 4,738 cases between 2011 and 2019—the largest total among the states included in the analysis. The state’s incidence increased significantly during that period.[2]
More recent surveillance confirms that the problem continues. The New York State Department of Health reported 670 confirmed or probable cases in 2024 outside New York City. The incidence increased from 3.4 to 5.9 cases per 100,000 residents, and cases were reported in 46 of the 57 counties outside New York City.[3]
These findings indicate that babesiosis has become an important public health concern throughout New York, particularly in regions where Lyme disease and other tick-borne infections are prevalent.
Hudson Valley Study Reveals Dramatic Increase in Babesia Cases
Babesia cases had previously been reported in counties east of the Hudson River, including Dutchess County and Westchester County. Westchester County alone has a population approaching 1 million residents.
Beginning in 2009, Babesia infections increased sharply in the Upper Hudson Valley region of New York, including Albany, Columbia, Greene, and Rensselaer counties.
Over the eight-year period between 2009 and 2016, the incidence of reported Babesia cases increased 16.8-fold in the Upper Hudson Valley.[1]
The number of cases also increased in the Lower Hudson Valley, which includes Dutchess, Putnam, Westchester, Orange, Rockland, Sullivan, and Ulster counties.
The Hudson Valley findings demonstrate how rapidly babesiosis can emerge in endemic areas and reflect a broader increase occurring across New York and the Northeast.
Why Babesia Infections May Be Underreported
The actual number of Babesia infections may be higher than surveillance figures suggest for several reasons:
- Babesia can be difficult to identify when the number of parasites circulating in the blood is low, making organisms harder to detect on a peripheral blood smear.
- Some infections cause mild or nonspecific symptoms and may never be tested.
- Cases may not be recognized if testing is delayed or incomplete.
- Not every diagnosed infection is successfully recorded through public health surveillance.
Joseph and colleagues concluded that babesiosis was rapidly emerging in the Hudson Valley, which had come to account for more cases than any other single region of New York State.[1]
The authors advised clinicians to consider babesiosis when compatible symptoms occur in patients who live in or have traveled to the Hudson Valley.
What Are the Symptoms of Babesiosis?
Symptoms of babesiosis may include fever, chills, fatigue, headaches, night sweats, anemia, shortness of breath, and dark urine. Some patients also describe a sensation of air hunger.
Some individuals remain asymptomatic or experience mild illness, while others develop significant complications. The risk of severe illness is greater among older adults and people who are immunocompromised or do not have a functioning spleen.
In endemic regions, babesiosis may occur alongside Lyme disease and other tick-borne infections. Learn more about Babesia infections, Lyme disease co-infections, and night sweats associated with tick-borne illness.
Why Babesia Matters in Patients With Lyme Disease
Babesia has important implications for patients with Lyme disease because the two infections can occur together and may complicate symptoms, diagnosis, and treatment decisions.
Unlike Lyme disease, babesiosis is caused by a parasite that infects red blood cells. Neither doxycycline nor amoxicillin treats Babesia. A patient with both infections may require a separate treatment regimen, commonly involving atovaquone combined with azithromycin.
Could Babesia duncani Be Contributing to the Rise?
The Joseph paper focused on Babesia microti, the species responsible for most reported cases in New York. Babesia duncani has traditionally been associated with the western United States.
Questions remain about whether exposure to Babesia duncani may occur beyond its historically recognized geographic range. Its prevalence and clinical importance in New York and other Northeastern states have not been established, and additional research is needed.
For additional discussion, see Babesia duncani emerges in eastern U.S. and poses treatment challenges.
Editor’s Perspective
I have practiced medicine in New York’s Hudson Valley since 1987 and have treated patients with Babesia infections for more than three decades.
Many of the earliest recognized patients with babesiosis were diagnosed when Babesia microti was identified inside red blood cells. In clinical practice, I consider antibody results alongside the patient’s symptoms, exposure history, blood smear or molecular testing when available, and other possible explanations for the illness.
A negative blood smear does not always exclude babesiosis, particularly when the level of parasites circulating in the blood is low. The Hudson Valley study and subsequent surveillance reports mirror the increasing number of Babesia infections I have observed during decades of treating tick-borne illnesses.
Frequently Asked Questions
Where are Babesia infections most common in New York?
Babesia infections have been reported across much of New York. The Hudson Valley study documented substantial increases in Albany, Columbia, Greene, and Rensselaer counties, while current surveillance shows cases across most counties outside New York City.
What are the most common symptoms of babesiosis?
Common symptoms include fever, chills, fatigue, headaches, night sweats, anemia, and shortness of breath. Some patients describe a sensation of air hunger, while others have mild symptoms or remain asymptomatic.
Can Babesia occur without Lyme disease?
Yes. Babesia can be transmitted independently of Lyme disease, although the two infections can occur together in endemic areas.
Can Babesia be missed on blood testing?
Yes. Parasites may not always be visible on a blood smear when the number circulating in the blood is low. Clinicians may consider additional testing and the overall clinical presentation when babesiosis remains a concern.
Clinical Takeaway
Babesia cases continue to increase across New York, and the infection is no longer limited to its historically recognized geographic pockets. The Hudson Valley study, national CDC analysis, and current New York surveillance data collectively demonstrate a sustained regional expansion.
Clinicians should consider babesiosis when compatible symptoms develop in patients who live in or have traveled to a Lyme-endemic region, even when an initial blood smear is negative.
Related Articles
Severe Babesia infection leads to exchange transfusion
Case series looks at the complexity of Babesia
Podcast: Two children who contracted Babesia from their mothers
References
- Joseph JT, John M, Visintainer P, Wormser GP. Increasing incidence and changing epidemiology of babesiosis in the Hudson Valley region of New York State: 2009-2016. Diagn Microbiol Infect Dis. 2020;96(2):114958.
- Swanson M, Pickrel A, Williamson J, Montgomery S. Trends in reported babesiosis cases—United States, 2011–2019. MMWR Morb Mortal Wkly Rep. 2023;72(11):273–277.
- New York State Department of Health. Tick-borne disease surveillance report, 2025. New York State Department of Health. 2025.
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
Hi Dr. Cameron. Just letting you know that when I was tested for Lyme (it took 4 mos to get a positive for BB) I was also tested more than once for Babesia but the tests were negative. I was told Babesia and Anaplasmosis were the most common co-infections in MN. When I went to the ER from the second nymph bites with a multiple lesion rash. I had red blotchy palms that prompted the ER doc to ask me “what’s that?” I said I didn’t know. Nothing said past that about it. I still have varying degree’s of blotchy palms since (7/17) I was wondering what the most prevalent clinical signs for Babesia look like in your studies. I know the sweats and chills for two years may be Babesia and would explain why Doxy didn’t work. Do Chronic Lyme patients need to be concerned about being exposed to COVID-19? Also I was recently rear ended and pushed into cars in front of me so there were two impacts that resulted in a diagnosis of whiplash and concussion. Is there anything I need to talk to my PT about concerning any other Lyme related conditions? I feel like I can’t say the word Lyme. It’s not being brought up as I am going through PT (Concussion therapy next). Is that because in MN there is still no protection for physicians to treat Lyme? I hear about people getting treated with a positive BB result but other than the original antibiotic treatment with Doxy, nothing has been brought up by any of my specialists or GP. (Only what I previously told you about Dr. Gary Bryant, Rheumatology at the U of M involved in the second attempt at a vaccine) That testing and treatments just aren’t there and he hopes to see it before he dies. I’m getting confusing messages but it would seem I may be in the wrong state to ask such questions. Most U of M physicians are IDSA members. Just wondering. Little nervous about going back to the hospital for PT today with the lack of discussion concerning Lyme, accident injuries and COVID-19. Lots in my questions and a bit of confusion but maybe you can take a crack at it. 🙂 Hope you are doing well. Stay safe.
I have patients in my practice who are equally confused and frustrated. I have to use clinical judgment as to whether to treat for a co-infection e.g., Babesia. I find that some of my Lyme disease patients do not realize they suffer from a tick-borne illness until they get a concussion. We do not know about COVID-19 and Lyme yet.
BTW I grew up in Minnesota. I practice in New York.
I live in northern California and back in the early 1990’s people came and tested our entire hillside community. The were a lot of positive results for lyme and babesia. My whole family was discovered to have babesia, but not lyme. All we were told at the time was to never donate blood. Is it possible that my siblings and I should be treated for babesia? Is it possible with treatment for me to be able to donate blood? Do you have recommendations for doctors in California?
I typically recommend an evaluation for Babesia and Lyme disease if I have a patient who is ill or never has been treated. I am not sure the blood back would clear you even if you are treated for Babesia. You could contact LymeDisease.org or ILADS.org.
Hi Doctor Cameron,
My ex husband knows you from Belizzi and Pizza Pizzazz and knows what a great doctor you are – he sent me here! I tested positive for Babesia microti last September (2021) and my titers were 1:20. They retested me in November (2021) and my titers were stable at 1:20. I still felt fatigue and unwell and just retested an my titers were 1:80. Do you think it’s time to begin treatment? If so, I look forward to seeing you soon.
We live in southern Ulster County. My daughter was first infected with Babesia in 2010 at age five. Her pediatrician recommended against treatment, citing CDC guidelines. When her initial symptoms were replaced with other ongoing concerns, we found a doctor willing to treat her four months after the infection began. She improved over the course of six months of medication, and we stopped treatment.
Over the years her IgG remained at 1:40 and she had several cycles of some symptoms and brief treatment. Last summer she had a new tick bite and confirmed Lyme, and her Babesia IgG went up to 1:320. She has had marked improvement with atovaquone and azithromycin, but is still struggling with symptoms. I wonder if it is something she will carry with her for the rest of her life to some degree.
I am happy to hear she had marked improvement with atovaquone and azithromycin. I have patients who have benefited from additional antibiotic treatment.