Babesiosis

Disease Information

Babesiosis is caused by microscopic parasites that infect red blood cells. Most human cases of Babesia infection in the United States are caused by the parasite Babesia microti. Occasional cases caused by other species (types) of Babesia have been detected.

Babesia microti is spread in nature by Ixodes scapularis ticks (also called blacklegged ticks or deer ticks). Tickborne transmission is most common in particular regions and seasons: it mainly occurs in parts of the Northeastern U.S. and upper Midwest; and it usually peaks during the warm months.

Babesia infection can range in severity from asymptomatic to life threatening. The infection is both treatable and preventable.

Disease Reporting

What is required?

Health Care Providers and Clinical Laboratories

Health care providers and clinical laboratories are required by law to report cases and suspect cases of babesiosis to local health departments within one working day of identification.

• Health care providers: Use our secure web-based confidential reporting system – OR – use the confidential PDF reporting form.
• See How and Where to Report for more information and local health department contacts.

For Tribal and Local Public Health Authorities

• Babesiosis Case Report Form (pdf)

See Also

• CDC's Basesiosis website