Tick-Borne Diseases

Lyme Disease: Data and Statistics

From 2019 to 2023, over 1,500 cases of Lyme disease were reported in Delaware. In 2023, 349 cases of Lyme disease were reported in Delaware for an incidence rate of 34 cases per 100,000 population.

Lyme Disease Case Counts and Incidence Rates by Year and County, Delaware, 2019-2023

	CASE COUNTS				INCIDENT RATE PER 100,000 POPULATION
YEAR	NEW CASTLE COUNTY	KENT COUNTY	SUSSEX COUNTY	DELAWARE	DELAWARE
2023	213	53	83	349	33.8
2022	192	54	52	298	29.3
2021	97	18	25	140	14.0
2020	250	43	61	354	35.8
2019	439	84	135	658	67.6
* These data include confirmed and probable cases according to national surveillance case definitions adopted by the Council of State and Territorial Epidemiologists (CSTE). The Lyme disease case definition, which was changed in 2022, may be found here. All rates are calculated per 100,000 population based on the U.S. Census Bureau’s population estimates (Current year incidence rates and case count subject to change when new population estimates are published, and data is finalized).

Source: Delaware Department of Health and Social Services, Division of Public Health, Office of Infectious Disease Epidemiology, Delaware Electronic Reporting and Surveillance System

Spotted Fever Group Rickettsiosis:

Data and Statistics

From 2019 to 2023, over 75 cases of Spotted Fever Group Rickettsiosis (SFGR) were reported in Delaware. In 2023, 5 cases of SFGR were reported in Delaware for an incidence rate of 0.5 cases per 100,000 population.

Spotted Fever Group Rickettsiosis Case Count and Incidence Rates by Year and County, Delaware, 2019-2023

	CASE COUNTS				INCIDENT RATE PER 100,000 POPULATION*
YEAR	NEW CASTLE COUNTY	KENT COUNTY	SUSSEX COUNTY	STATE	STATE
2023	1	0	4	5	0.5
2022	4	0	0	4	0.4
2021	7	1	11	19	1.9
2020	4	5	10	19	1.9
2019	18	5	13	36	3.7
* Rates based on small numbers (less than 20) result in a large relative standard error, indicating an imprecise estimate that is unstable and unreliable. + These data include confirmed and probable cases according to national surveillance case definitions adopted by the Council of State and Territorial Epidemiologists (CSTE). The Spotted Fever Group Rickettsiosis (SFGR) case definition may be found here. Spotted Fever Group Rickettsiosis was previously called Rocky Mountain Spotted Fever. All rates are calculated per 100,000 population based on the U.S. Census Bureau’s population estimates (Current year incidence rates and case count subject to change when new population estimates are published, and data is finalized).

Source: Delaware Department of Health and Social Services, Division of Public Health, Office of Infectious Disease Epidemiology, Delaware Electronic Reporting and Surveillance System