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.
![Adult blacklegged tick](/babesiosis/media/images/28371-i-scapularis-adult.png)
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, 2014–2020*
2014 |
2015 |
2016 |
2017 |
2018 |
2019 |
2020 |
||||||||
State† |
No. |
Rate |
No. |
Rate |
No. |
Rate |
No. |
Rate |
No. |
Rate |
No. |
Rate |
No. |
Rate |
Alabama |
1 |
<0.1 |
2 |
<0.1 |
0 |
0.0 |
1 |
<0.1 |
0 |
0 |
0 |
0 |
0 |
0 |
Alaska§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
Arizona |
— |
— |
— |
— |
— |
— |
— |
— |
0 |
0 |
0 |
0 |
0 |
0 |
Arkansas |
— |
— |
0 |
0.0 |
1 |
<0.1 |
0 |
0.0 |
2 |
<0.1 |
1 |
<0.1 |
0 |
0 |
California |
3 |
<0.1 |
5 |
<0.1 |
3 |
<0.1 |
4 |
<0.1 |
6 |
<0.1 |
2 |
<0.1 |
1 |
<0.1 |
Colorado§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
Connecticut |
205 |
5.7 |
328 |
9.1 |
322 |
9.0 |
309 |
8.6 |
248 |
6.9 |
323 |
9.0 |
151 |
4.2 |
Delaware |
1 |
0.1 |
1 |
0.1 |
2 |
0.2 |
4 |
0.4 |
3 |
0.3 |
3 |
0.3 |
4.0 |
0.4 |
District of Columbia |
— |
— |
— |
— |
— |
— |
— |
— |
2 |
0.3 |
0 |
0.0 |
0 |
0 |
Florida |
— |
— |
— |
— |
— |
— |
9 |
<0.1 |
19 |
<0.1 |
24 |
<0.1 |
2 |
<0.1 |
Georgia |
— |
— |
— |
— |
— |
— |
— |
— |
0 |
0 |
1 |
<0.1 |
0 |
0 |
Hawaii§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
Idaho§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
Illinois |
1 |
<0.1 |
3 |
<0.1 |
2 |
<0.1 |
0 |
0.0 |
1 |
<0.1 |
1 |
<0.1 |
5 |
<0.1 |
Indiana |
0 |
0.0 |
0 |
0.0 |
0 |
0.0 |
1 |
<0.1 |
1 |
<0.1 |
0 |
0.00 |
1 |
<0.1 |
Iowa |
— |
— |
— |
— |
— |
— |
2 |
0.1 |
0 |
0 |
0 | 0 |
1 |
<0.1 |
Kansas |
— |
— |
— |
— |
— |
— |
— |
— |
0 |
0 |
0 |
0 |
0 |
0 |
Kentucky |
— |
— |
0 |
0.0 |
0 |
0.0 |
0 |
0.0 |
0 |
0 |
0 |
0 |
0 |
0 |
Louisiana |
0 |
0.0 |
1 |
<0.1 |
0 |
0.0 |
1 |
<0.1 |
1 |
<0.1 |
0 |
0 |
0 |
<0.1 |
Maine |
42 |
3.2 |
55 |
4.1 |
82 |
6.2 |
118 |
8.8 |
101 |
7.5 |
138 |
10.3 |
66 |
4.8 |
Maryland |
2 |
<0.1 |
4 |
0.1 |
6 |
0.1 |
5 |
<0.1 |
7 |
0.1 |
7 |
0.1 |
9 |
<0.1 |
Massachusetts |
535 |
7.9 |
444 |
6. |
517 |
7.6 |
591 |
8.6 |
527 |
7.6 |
636 |
9.2 |
580 |
8.3 |
Michigan |
2 |
<0.1 |
3 |
<0.1 |
2 |
<0.1 |
3 |
<0.1 |
1 |
<0.1 |
1 |
<0.1 |
0 |
0 |
Minnesota |
49 |
0.9 |
45 |
0.8 |
50 |
0.9 |
60 |
1.1 |
49 |
0.9 |
55 |
1.0 |
— |
— |
Mississippi§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
Missouri |
— |
— |
— |
— |
1 |
<0.1 |
0 |
0.0 |
0 |
0 |
1 |
<0.1 |
0 |
0 |
Montana |
0 |
0.0 |
0 |
0.0 |
1 |
0.1 |
0 |
0.0 |
0 |
0 |
0 |
0 |
0 |
0 |
Nebraska |
0 |
0.0 |
0 |
0.0 |
1 |
0.1 |
0 |
0.0 |
0 |
0 |
0 |
0 |
0 |
0 |
Nevada§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
New Hampshire§ |
42 |
3.2 |
53 |
4.0 |
13 |
1.0 |
78 |
5.8 |
37 |
2.7 |
63 |
4.6 |
28 |
2.0 |
New Jersey |
159 |
1.8 |
281 |
3.1 |
174 |
1.9 |
193 |
2.1 |
247 |
2.8 |
236 |
2.6 |
237 |
2.6 |
New Mexico§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
New York |
471 |
2.4 |
581 |
2.9 |
430 |
2.2 |
696 |
3.5 |
641 |
3.3 |
663 |
3.4 |
461 |
2.3 |
North Carolina§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
North Dakota |
0 |
0.0 |
3 |
0.4 |
1 |
0.1 |
0 |
0.0 |
1 |
0.1 |
0 |
0.0 |
0 |
0.0 |
Ohio |
1 |
<0.1 |
2 |
<0.1 |
— |
— |
1 |
<0.1 |
4 |
<0.1 |
4 |
<0.1 |
1 |
<0.1 |
Oklahoma§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
Oregon |
1 |
<0.1 |
2 |
<0.1 |
2 |
<0.1 |
5 |
0.1 |
2 |
<0.1 |
2 |
<0.1 |
4 |
0.1 |
Pennsylvania§ |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
— |
Rhode Island |
172 |
16.3 |
190 |
18.0 |
155 |
14.7 |
161 |
15.2 |
165 |
15.6 |
158 |
14.9 |
193 |
17.6 |
South Carolina |
3 |
0.1 |
2 |
<0.1 |
2 |
<0.1 |
2 |
<0.1 |
1 |
<0.1 |
0 |
0 |
0 |
0 |
South Dakota |
1 |
0.1 |
0 |
0.0 |
0 |
0.0 |
0 |
0.0 |
0 |
0 |
0 |
0 |
1 |
<0.1 |
Tennessee |
0 |
0.0 |
1 |
<0.1 |
1 |
<0.1 |
1 |
<0.1 |
1 |
<0.1 |
1 |
<0.1 |
1 |
<0.1 |
Texas |
1 |
<0.1 |
1 |
<0.1 |
1 |
<0.1 |
0 |
0.0 |
2 |
<0.1 |
2 |
<0.1 |
3 |
<0.1 |
Utah |
0 |
0.0 |
0 |
0.0 |
0 |
0.0 |
1 |
<0.1 |
1 |
<0.1 |
0 |
0 |
0 |
0 |
Vermont |
3 |
0.5 |
9 |
1.4 |
15 |
2.4 |
22 |
3.5 |
21 |
3.4 |
34 |
5.4 |
16 |
2.5 |
Virginia |
— |
— |
— |
— |
— |
— |
0 |
0.0 |
5 |
<0.1 |
1 |
<0.1 |
3 |
<0.1 |
Washington |
4 |
0.1 |
2 |
<0.1 |
0 |
0.0 |
1 |
<0.1 |
0 |
0 |
1 |
<0.1 |
0 |
0 |
West Virginia |
0 |
0.0 |
0 |
0.0 |
0 |
0.0 |
1 |
0.1 |
1 |
<0.1 |
0 |
<0.1 |
0 |
0 |
Wisconsin |
43 |
0.7 |
56 |
1.0 |
68 |
1.2 |
88 |
1.5 |
64 |
1.1 |
58 |
1.0 |
57 |
1.0 |
Wyoming |
0 |
0.0 |
0 |
0.0 |
0 |
0.0 |
0 |
0.0 |
0 |
0 |
0 |
0 |
1 |
<0.1 |
Total¶# |
1,742 |
0.8 |
2,074 |
0.9 |
1,909 |
0.8 |
2,358 |
0.9 |
2,161 |
0.77 |
2,418 |
0.86 |
1,827 |
0.65 |