This parasitic infection arises from intraerythrocytic protozoa that invade and replicate within red blood cells [2]. It is classified among vector-borne infectious diseases and shares biological characteristics with other hemolytic parasitic conditions [3][4].
Disease overview
ParasiticBabesiosis
巴贝西虫病
Evidence-backed informationEN 5/7 applicable sections · ZH 5/7 applicable sectionsUpdated Sep 3, 2026
Babesiosis is a globally emerging parasitic illness transmitted mainly by ticks, with expanding geographic reach and rising case frequencies [1][2]. The condition places considerable strain on public health systems, particularly affecting individuals with weakened immune defenses or those who contract the pathogen via blood products [1]. While generally manageable, the infection carries substantial mortality risks within vulnerable populations [2].
Read the full clinical and epidemiological profile6
Clinical manifestations closely mimic malaria, and the infection can be fatal in immunocompromised and older patients [2]. Diagnosis is confirmed by identification of typical intraerythrocytic parasites on a thin blood smear or by detection of Babesia DNA using PCR [1][2].
The disease occurs worldwide but demonstrates markedly higher incidence rates in the northeastern and upper midwestern regions of the United States [2]. Its prevalence and geographic distribution are actively expanding, establishing it as an emerging public health concern [1]. Significant morbidity and mortality burdens are concentrated among immunocompromised individuals and recipients of contaminated blood transfusions, with fatality rates approaching twenty percent in these cohorts [1].
Primary spread occurs through the bite of infected ticks [2]. Secondary routes include infrequent transmission via blood transfusions and rare instances of vertical or organ transplant-related passage [2]. These pathways highlight both vector-driven and iatrogenic mechanisms of pathogen dissemination [1].
Public health strategies emphasize individual and community-level interventions designed to reduce tick exposure and mitigate infection rates [1]. Despite these efforts, current protective approaches are unlikely to halt the ongoing ecological spread of the parasite into previously unaffected regions [1].
- 1Krause PJ et al. Human babesiosis. Int J Parasitol. 2019 Feb. PMID: 30690090. doi: 10.1016/j.ijpara.2018.11.007.PubMed: https://pubmed.ncbi.nlm.nih.gov/30690090/
- 2Waked R et al. Human Babesiosis. Infect Dis Clin North Am. 2022 Sep. PMID: 36116841. doi: 10.1016/j.idc.2022.02.009.PubMed: https://pubmed.ncbi.nlm.nih.gov/36116841/
- 3Dhaliwal G et al. Hemolytic anemia. Am Fam Physician. 2004 Jun 1. PMID: 15202694.PubMed: https://pubmed.ncbi.nlm.nih.gov/15202694/
- 4Theel ES et al. Parasites. Microbiol Spectr. 2016 Aug. PMID: 27726821. doi: 10.1128/microbiolspec.DMIH2-0013-2015.PubMed: https://pubmed.ncbi.nlm.nih.gov/27726821/
Coverage
Reporting countries and regions
Trends by reporting country
Monthly patterns over time
Data access
Page dataset index with source links and update metadata.
Official sourcesAuthority, cadence, notes3
Public Health Ontario IDTO Monthly
Ontario, Canada
Ontario-level current-year preliminary monthly case counts from Public Health Ontario's IDTO report.
US CDC NNDSS
United States
CDC National Notifiable Diseases Surveillance System provisional data.
US CDC NHSS HIV
United States
CDC NNDSS weekly data plus NHSS annual national HIV diagnoses