At a glance
Babesiosis is a disease caused by microscopic parasites that infect red blood cells. Many different species (types) of Babesia parasites have been found in animals, only a few of which have been found in people. Babesia microti—which usually infects white-footed mice and other small mammals—is the main species that has been found in people in the United States. Occasional cases caused by other Babesia species have been detected.
Annual Summaries
- Surveillance for Babesiosis – United States, 2020 (February 6, 2023)
- Surveillance for Babesiosis – United States, 2019 (August 12, 2021)
- Surveillance for Babesiosis – United States, 2018 (April 22, 2019)
- Surveillance for Babesiosis – United States, 2017 (June 27, 2019)
- Surveillance for Babesiosis – United States, 2016 (June 27, 2019)
- Surveillance for Babesiosis – United States, 2015 (June 27, 2019)
- Surveillance for Babesiosis – United States, 2014 (February 29, 2016)
Number and incidence of reported cases of Babesiosis
Number and incidence of reported cases of babesiosis, by state and year, 2014–2023*
| 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 | 2014 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| State† | No. | Rate | No. | Rate | No. | Rate | No. | Rate | No. | Rate | No. | Rate | No. | Rate | No. | Rate | No. | Rate | No. | Rate |
| Alabama | 1 | <0.1 | 0 | 0 | 1 | <0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | <0.1 | 0 | 0 | 2 | <0.1 | 1 | <0.1 |
| Alaska§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Arizona | 3 | <0.1 | 2 | <0.1 | 3 | <0.1 | 0 | 0 | 0 | 0 | 0 | 0 | — | — | — | — | — | — | — | — |
| Arkansas | 2 | 0.1 | 1 | <0.1 | 2 | 0.1 | 0 | 0 | 1 | <0.1 | 2 | <0.1 | 0 | 0 | 1 | <0.1 | 0 | 0 | — | — |
| California | 10 | <0.1 | 7 | <0.1 | 3 | <0.1 | 1 | <0.1 | 2 | <0.1 | 6 | <0.1 | 4 | <0.1 | 3 | <0.1 | 5 | <0.1 | 3 | <0.1 |
| Colorado§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Connecticut | 246 | 6.8 | 115 | 3.2 | 281 | 7.8 | 151 | 4.2 | 323 | 9.0 | 248 | 6.9 | 309 | 8.6 | 322 | 9.0 | 328 | 9.1 | 205 | 5.7 |
| Delaware | 3 | 0.3 | 0 | 0 | 4 | 0.4 | 4.0 | 0.4 | 3 | 0.3 | 3 | 0.3 | 4 | 0.4 | 2 | 0.2 | 1 | 0.1 | 1 | 0.1 |
| District of Columbia |
3 | 0.4 | 1 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 2 | 0.3 | — | — | — | — | — | — | — | — |
| Florida | 36 | 0.2 | 18 | 0.1 | 19 | 0.1 | 2 | <0.1 | 24 | <0.1 | 19 | <0.1 | 9 | <0.1 | — | — | — | — | — | — |
| Georgia | — | — | — | — | — | — | 0 | 0 | 1 | <0.1 | 0 | 0 | — | — | — | — | — | — | — | — |
| Hawaii§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Idaho§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Illinois | 13 | 0.1 | 8 | 0.1 | 8 | 0.1 | 5 | <0.1 | 1 | <0.1 | 1 | <0.1 | 0 | 0 | 2 | <0.1 | 3 | <0.1 | 1 | <0.1 |
| Indiana | 2 | <0.1 | 0 | 0 | 1 | <0.1 | 1 | <0.1 | 0 | 0 | 1 | <0.1 | 1 | <0.1 | 0 | 0 | 0 | 0 | 0 | 0 |
| Iowa | 5 | 0.2 | 3 | 0.1 | 5 | 0.2 | 1 | <0.1 | 0 | 0 | 0 | 0 | 2 | 0.1 | — | — | — | — | — | — |
| Kansas | 1 | <0.1 | 0 | 0 | 2 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0 | — | — | — | — | — | — | — | — |
| Kentucky | 0 | 0 | 0 | 0 | 2 | <0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | — | — |
| Louisiana | 0 | 0 | 0 | 0 | 1 | <0.1 | 0 | <0.1 | 0 | 0 | 1 | <0.1 | 1 | <0.1 | 0 | 0 | 1 | <0.1 | 0 | 0 |
| Maine | 196 | 14 | 193 | 13.9 | 201 | 14.6 | 66 | 4.8 | 138 | 10.3 | 101 | 7.5 | 118 | 8.8 | 82 | 6.2 | 55 | 4.1 | 42 | 3.2 |
| Maryland | 29 | 0.5 | 7 | 0.1 | 13 | 0.2 | 9 | 0.1 | 7 | 0.1 | 7 | 0.1 | 5 | <0.1 | 6 | 0.1 | 4 | 0.1 | 2 | <0.1 |
| Massachusetts | 841 | 11.9 | 451 | 6.4 | 611 | 8.7 | 580 | 8.3 | 636 | 9.2 | 527 | 7.6 | 591 | 8.6 | 517 | 7.6 | 444 | 6.5 | 535 | 7.9 |
| Michigan | 10 | 0.1 | 9 | 0.1 | 4 | 0 | 0 | 0 | 1 | <0.1 | 1 | <0.1 | 3 | <0.1 | 2 | <0.1 | 3 | <0.1 | 2 | <0.1 |
| Minnesota | 73 | 1.3 | 61 | 1.1 | 63 | 1.1 | — | — | 55 | 1.0 | 49 | 0.9 | 60 | 1.1 | 50 | 0.9 | 45 | 0.8 | 49 | 0.9 |
| Mississippi§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Missouri | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | <0.1 | 0 | 0 | 0 | 0 | 1 | <0.1 | — | — | — | — |
| Montana | 0 | 0 | 1 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0.1 | 0 | 0 | 0 | 0 |
| Nebraska | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0.1 | 0 | 0 | 0 | 0 |
| Nevada§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| New Hampshire§ | 53 | 3.8 | 58 | 4.2 | 80 | 5.8 | 28 | 2.0 | 63 | 4.6 | 37 | 2.7 | 78 | 5.8 | 1.3 | 1.0 | 53 | 4.0 | 42 | 3.2 |
| New Jersey | 406 | 4.3 | 292 | 3.1 | 258 | 2.8 | 237 | 2.6 | 236 | 2.6 | 247 | 2.8 | 193 | 2.1 | 174 | 1.9 | 281 | 3.1 | 159 | 1.8 |
| New Mexico§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| New York | 1,169 | 5.9 | 589 | 3 | 793 | 4 | 461 | 2.3 | 663 | 3.4 | 641 | 3.3 | 696 | 3.5 | 430 | 2.2 | 581 | 2.9 | 471 | 2.4 |
| North Carolina§ | 0 | 0 | 0 | 0 | 0 | 0 | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| North Dakota | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0.1 | 0 | 0 | 1 | 0.1 | 3 | 0.4 | 0 | 0 |
| Ohio | 5 | <0.1 | 4 | <0.1 | 3 | <0.1 | 1 | <0.1 | 4 | <0.1 | 4 | <0.1 | 1 | <0.1 | — | — | 2 | <0.1 | 1 | <0.1 |
| Oklahoma§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Oregon | 6 | 0.1 | 1 | <0.1 | 3 | 0 | 4 | 0.1 | 2 | <0.1 | 2 | <0.1 | 5 | 0.1 | 2 | <0.1 | 2 | <0.1 | 1 | <0.1 |
| Pennsylvania§ | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — |
| Rhode Island | 242 | 21.9 | 118 | 10.7 | 195 | 17.8 | 193 | 17.6 | 158 | 14.9 | 165 | 15.6 | 161 | 15.2 | 155 | 14.7 | 190 | 18 | 172 | 16.3 |
| South Carolina | 2 | <0.1 | 2 | <0.1 | 3 | 0.1 | 0 | 0 | 0 | 0 | 1 | <0.1 | 2 | <0.1 | 2 | <0.1 | 2 | <0.1 | 3 | 0.1 |
| South Dakota | 1 | 0.1 | 0 | 0 | 0 | 0 | 1 | <0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0.1 |
| Tennessee | 3 | <0.1 | 1 | <0.1 | 2 | <0.1 | 1 | <0.1 | 1 | <0.1 | 1 | <0.1 | 1 | <0.1 | 1 | <0.1 | 1 | <0.1 | 0 | 0 |
| Texas | 3 | <0.1 | 4 | <0.1 | 1 | <0.1 | 3 | <0.1 | 2 | <0.1 | 2 | <0.1 | 0 | 0 | 1 | <0.1 | 1 | <0.1 | 1 | <0.1 |
| Utah | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | <0.1 | 1 | <0.1 | 0 | 0 | 0 | 0 | 0 | 0 |
| Vermont | 81 | 12.5 | 60 | 9.3 | 2 | 0.3 | 16 | 2.5 | 34 | 5.4 | 21 | 3.4 | 22 | 3.5 | 15 | 2.4 | 9 | 1.4 | 3 | 0.5 |
| Virginia | 11 | 0.1 | 11 | 0.1 | 11 | 0.1 | 3 | <0.1 | 1 | <0.1 | 5 | <0.1 | 0 | 0 | — | — | — | — | — | — |
| Washington | 2 | <0.1 | 1 | <0.1 | 0 | 0 | 0 | 0 | 1 | <0.1 | 0 | 0 | 1 | <0.1 | 0 | 0 | 2 | <0.1 | 4 | 0.1 |
| West Virginia | 2 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | <0.1 | 1 | <0.1 | 1 | 0.1 | 0 | 0 | 0 | 0 | 0 | 0 |
| Wisconsin | 124 | 2.1 | 9.1 | 1.5 | 99 | 1.7 | 57 | 1.0 | 58 | 1.0 | 64 | 1.1 | 88 | 1.5 | 68 | 1.2 | 56 | 1 | 43 | 0.7 |
| Wyoming | 2 | 0.3 | 2 | 0.3 | 0 | 0 | 1 | <0.1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Total¶# | 3,586 | 1.06 | 2,111 | 0.63 | 2,674 | 0.81 | 1,827 | 0.65 | 2,418 | 0.86 | 2,161 | 0.77 | 2,358 | 0.9 | 1,909 | 0.8 | 2,074 | 0.9 | 1,742 | 0.8 |
* Year as reported by the health department
† Cases were reported by state of residence, which was not necessarily the state of exposure.
‡ Rate per 100,000 population
§ Babesiosis is not a reportable condition by law in these states.
¶ The denominators for calculations of total incidence rates included only the populations of states in which babesiosis was a reportable condition during the pertinent year.
# 2020 data may be lower or higher than previous years. COVID-19 likely had an impact on public health activities including case identification and case investigations, as well as possibly impacting transmission rates. Data changes may reflect the impact of isolation and prevention measures, whether people sought health care when they were ill, and other changes in behavior during the COVID-19 pandemic period.