Ohio Vector-borne Disease Surveillance Update

The Ohio Department of Health (ODH) Zoonotic & Vector-borne Diseases section, in partnership with ODH Laboratory, local public health partners, and sanitary district partners, conducts statewide vector-borne disease surveillance which includes monitoring for human and veterinary cases.

We will monitor for diseases transmitted by mosquitoes and ticks throughout the summer and fall and will report positive results and summary statistics on this website, updated each Friday at noon.

For more data on human cases of mosquito-borne and tickborne diseases, please visit ODH's infectious disease dashboard.

As of September 24, 2026.

2026 Mosquito-borne Diseases

West Nile Virus

Mosquito surveillance:

Mosquitoes tested from 55 agencies in 47 counties, pooled into 15,458* samples.

West Nile virus positive mosquito pools from 36 counties:

Ashtabula (7), Athens (1), Belmont (1), Cuyahoga (104), Fairfield (18), Franklin (773), Greene (14), Guernsey (1), Hamilton (34), Lake (12), Licking (3), Lorain (79), Lucas (422), Marion (3), Medina (14), Miami (2), Monroe (2), Montgomery (13), Morgan (1), Muskingum (1), Noble (1), Ottawa (120), Perry (1), Portage (15), Richland (18), Ross (6), Sandusky (4), Scioto (39), Shelby (6), Stark (102), Summit (58), Trumbull (1), Tuscarawas (3), Warren (4), Williams (1), Wyandot (2).

* In addition to samples tested by the Ohio Department of Health, Columbus Public Health, Delaware Public Health District, Franklin County Public Health, Licking County Health Department, and Toledo Area Sanitary District tested some of their samples.

Human surveillance:

West Nile virus disease human cases.

Sexes:

Ages:

From 12 counties:

Allen (1), Ashland (1), Cuyahoga (2), Franklin (2), Greene (1), Hamilton (1), Lucas (1), Miami (1), Montgomery (1), Paulding (1), Richland (1), Wood (1).

Asymptomatic, viremic blood donor.

Veterinary surveillance:

West Nile virus avian case.

West Nile virus equine cases.

La Crosse/California encephalitis virus

Mosquito surveillance:

Mosquitoes tested from 49 agencies in 42 counties pooled into 1,496 samples.

La Crosse virus positive mosquito pools from 2 counties:

Ross (2), Tuscarawas (1).

Human surveillance:

La Crosse virus disease human cases.

Sexes:

Ages:

From 9 counties:

Franklin (1), Holmes (1), Morgan (1), Muskingum (1), Pickaway (1), Pike (1), Richland (1), Ross (2), Wayne (2).

Travel-associated mosquito-borne diseases

Chikungunya surveillance:

Chikungunya human case.

Sexes:

Traveled to 1 country:

Tanzania (1).

Dengue surveillance:

Dengue human case.

Sexes:

Traveled to 1 country:

Honduras (1).

Zika surveillance:

Zika human cases.

Malaria surveillance:

Malaria human cases.

Sexes:

Ages:

Traveled to 14 countries:

Brazil (1), Cameroon (5), Ethiopia (1), Gabon (2), Ghana (3), Guinea (3), Indonesia (1), Liberia (2), Nigeria (7), Rwanda (1), Sierra Leone (11), Sudan (2), Tanzania (1), Togo (1), unknown country (2).

* Ohioans traveling to areas where local transmission is occurring should be aware of the ongoing situation and make every effort to avoid mosquito bites. Additional information can be found from the Centers for Disease Control and Prevention (CDC)'s Travelers' Health and Pan-American Health Organization websites.

2026 Tickborne Diseases

Lyme disease, anaplasmosis, babesiosis

Tick surveillance:

Blacklegged ticks identified.

From 53 counties:

Ashland (5), Ashtabula (420), Athens (16), Belmont (1), Butler (10), Clark (1), Clermont (5), Clinton (1), Columbiana (3), Coshocton (2), Crawford (1), Cuyahoga (9), Delaware (1), Erie (9), Fairfield (6), Franklin (8), Fulton (1), Gallia (1), Geauga (2), Greene (1), Guernsey (2), Hamilton (20), Harrison (4), Highland (1), Hocking (11), Holmes (3), Jefferson (1), Knox (1), Lake (9), Licking (112), Lorain (2), Lucas (848), Mahoning (3), Marion (1), Medina (9), Meigs (7), Monroe (3), Montgomery (1), Morgan (2), Muskingum (1), Perry (4), Pickaway (12), Portage (19), Richland (3), Scioto (1), Stark (10), Summit (12), Trumbull (1), Tuscarawas (6), Warren (1), Washington (63), Wayne (2), Wyandot (1).

Lyme disease human surveillance:

Lyme disease human cases.

Sexes:

Ages:

From 73 counties:

Ashland (18), Ashtabula (13), Athens (67), Belmont (189), Brown (2), Butler (8), Carroll (28), Clark (4), Clermont (24), Columbiana (124), Coshocton (52), Cuyahoga (37), Darke (1), Defiance (2), Delaware (16), Erie (9), Fairfield (55), Fayette (1), Franklin (55), Fulton (2), Gallia (10), Geauga (24), Greene (3), Guernsey (39), Hamilton (20), Harrison (47), Highland (1), Hocking (9), Holmes (35), Huron (2), Jackson (10), Jefferson (131), Knox (37), Lake (25), Lawrence (8), Licking (98), Logan (5), Lorain (7), Lucas (10), Madison (3), Mahoning (47), Marion (2), Medina (26), Meigs (22), Mercer (1), Miami (2), Monroe (12), Montgomery (8), Morgan (29), Morrow (12), Muskingum (69), Noble (17), Ottawa (3), Perry (18), Pike (3), Portage (31), Preble (3), Putnam (1), Richland (39), Ross (13), Sandusky (1), Scioto (9), Seneca (3), Stark (103), Summit (54), Trumbull (26), Tuscarawas (95), Union (1), Vinton (2), Warren (1), Washington (2), Wayne (44), Wood (5).

Anaplasmosis human surveillance:

Anaplasmosis human cases.

Sexes:

Ages:

From 23 counties:

Adams (1), Belmont (1), Carroll (3), Columbiana (8), Coshocton (2), Cuyahoga (2), Delaware (1), Franklin (1), Gallia (1), Harrison (3), Holmes (1), Jefferson (2), Logan (1), Lorain (1), Madison (1), Meigs (1), Monroe (1), Portage (1), Scioto (2), Stark (1), Summit (1), Trumbull (1), Tuscarawas (2).

Babesiosis human surveillance:

Babesiosis human cases.

Sexes:

Ages:

From 3 counties:

Belmont (1), Lake (1), Tuscarawas (1).

Rocky Mountain spotted fever (RMSF)

Tick surveillance:

American dog ticks identified.

Human surveillance:

RMSF human cases.

Sexes:

Ages:

From 16 counties:

Athens (1), Brown (1), Butler (1), Clermont (1), Franklin (1), Gallia (4), Jackson (5), Knox (1), Lake (1), Lucas (1), Meigs (1), Pike (2), Ross (1), Scioto (2), Vinton (1), Warren (1).

Ehrlichiosis

Tick surveillance:

Lone Star ticks identified.

Human surveillance:

Ehrlichiosis human cases.

Sexes:

Ages:

From 19 counties:

Adams (1), Athens (2), Columbiana (1), Fairfield (1), Franklin (2), Gallia (3), Geauga (1), Greene (3), Hamilton (2), Harrison (1), Jackson (5), Lake (1), Lawrence (2), Lorain (1), Meigs (1), Montgomery (1), Muskingum (1), Ross (4), Scioto (4), unknown county (1).