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. (Table 1). 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.
Table 1. West Nile Virus 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 | 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 |
| * 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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