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Delaware Health Alert Network #100

August 18, 2005 4:00 PM

Health Advisory

The Delaware Division of Public Health (DPH) wishes to alert the Delaware medical community of two sentinel chickens that tested positive earlier this week for Eastern Equine Encephalitis (EEE). These are the first reported cases in 2005 of EEE in Delaware. Last week five cases of Eastern Equine Encephalitis (EEE) were reported in horses in the southeast corner of Virginia. There have been no confirmed human cases of EEE in Delaware since 1979.


Surveillance for EEE in Delaware is accomplished through periodic testing of sentinel chicken flocks. The two EEE positive sentinel chickens are from a flock maintained in the Cypress Swamp area of Sussex County, Delaware. Delaware does not routinely test mosquitoes for EEE.

Clinical Description:

Eastern Equine Encephalitis (EEE) is a mosquito-transmitted virus causing acute febrile illness. Symptoms range from a headache and mild flu-like illness to encephalitis (inflammation of the brain), coma and death. The EEE case fatality rate (the percentage of persons who develop the disease who will die) is 35%, making it one of the most pathogenic mosquito-borne diseases in the United States. It is estimated that 35% of people who survive EEE will have mild to severe neurologic deficits. There is no specific treatment for EEE.

Risk Groups:

Those at increased risk for developing EEE are residents of and visitors to endemic areas and people who engage in outdoor work and recreational activities. Persons over age 50 and younger than age 15 seem to be at greatest risk for developing severe disease.

Incubation Period:

Incubation period is usually 5-15 days.

Period of Communicability:

There is no direct person-to-person transmission. Viremia in horses is short-lived and horses are not implicated as a reservoir for human infection.

Laboratory Criteria for Diagnosis:

Detection of the presence of EEE is made by demonstration of specific IgM in acute phase serum or CSF, or rises in antibody titer between early and late serum specimens by serological testing methods.


People should avoid mosquito bites by employing personal and household protection measures, such as using insect repellent containing DEET or Picaridin, wearing protective clothing, taking precautions from dusk to dawn when mosquitoes are most likely to bite and controlling standing water that can provide mosquito-breeding sites. There is an available vaccine to protect horses. More information is available on mosquito bite avoidance at:

Reporting of Suspect Cases:

To aid in surveillance, the Delaware Division of Public Health (DPH) requests that health care providers be suspicious of patients presenting with clinically compatible illness and report suspicious cases and laboratory confirmed EEE infections to DPH, Bureau of Epidemiology at 1-888-295-5156. The number is available during normal business hours and during non-business hours for emergencies.

For Further Information:

  • DPH, Bureau of Epidemiology at 1-888-295-5156. The number is available during normal business hours and during non-business hours for emergencies.
  • For animal health related information, the Delaware Department of Agriculture can be reached at 1-800-286-8685.

Categories of Health Alert messages:

  • Health Alert: Conveys the highest level of importance; warrants immediate action or attention.
  • Health Advisory: Provides important information for a specific incident or situation; may not require immediate action.
  • Health Update: Provides updated information regarding an incident or situation; unlikely to require immediate action.
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