Mosquito-Borne Diseases Data Statistics

West Nile Virus: Data and Statistics

In 2023, 4 cases of West Nile virus (WNV) disease, were reported in Delaware for an incidence rate of 0.4 cases per 100,000 population. All cases in 2023 were neuroinvasive cases. Cases of mild illness (non-neuroinvasive disease) are more likely to be underreported compared to more severe disease (neuroinvasive) cases. For the reporting period from 2018 to 2023, 18 cases of WNV disease were reported (Table 1).

Table 1. West Nile Virus Disease Case Counts and Incidence Rates by Year and County, Delaware, 2018-2023

	CASE COUNTS				INCIDENT RATE PER 100,000 POPULATION*
YEAR	NEW CASTLE COUNTY	KENT COUNTY	SUSSEX COUNTY	DELAWARE	DELAWARE
2023	4	0	0	4	0.4
2022	0	0	1	1	0.1
2021	0	2	1	3	0.3
2020	0	0	0	0	0.0
2019	0	0	0	0	0.0
2018	7	1	2	10	1.0
* 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 arboviral disease case definition which includes WNV, 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

Other Mosquito-Borne Diseases: Data and Statistics

Table 2. Mosquito-Borne Disease Case Counts and Incidence Rates by Travel Status, Delaware, 2023

DISEASE	TRAVEL-ASSOCIATED CASE COUNTS	LOCALLY ACQUIRED CASE COUNTS	DELAWARE CASE COUNTS	DELAWARE INCIDENCE RATE PER 100,000 POPULATION*
Chikungunya	0	0	0	0.0
Dengue	5	0	5	0.5
Eastern Equine Encephalitis	0	0	0	0.0
Jamestown Canyon	0	0	0	0.0
La Crosse Encephalitis	0	0	0	0.0
Malaria	13	0	13	1.3
St. Louis Encephalitis	0	0	0	0.0
Yellow Fever	0	0	0	0.0
Zika	0	0	0	0.0
* 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 arboviral disease case definition which includes WNV, 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

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Mosquito-Borne Diseases Data Statistics

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West Nile Virus: Data and Statistics

Other Mosquito-Borne Diseases: Data and Statistics

Table 2. Mosquito-Borne Disease Case Counts and Incidence Rates by Travel Status, Delaware, 2023

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