Surveillance - Disease Carrying Insects Program
Surveillance is one of the key components of the Disease Carrying Insects Program (DCIP). Information on mosquitoes and ticks is gathered daily and analyzed on a weekly basis using a variety of sampling and analytical methods. The resulting data are used to monitor public health risk levels and enable the Health Department to act quickly when these risk levels are elevated. Traps are set up throughout the Fairfax community.
Mosquito trap data are associated with risk factors in order to assess and predict human risk and determine "triggers" for mosquito control activities. Adult mosquito trapping can be expanded or enhanced when routine surveillance methods detect West Nile virus activity. This helps determine zones of potential local transmission and the extent of viral activity, thus guiding interventions.
Larval surveillance activities are currently targeted at Culex mosquitoes and include identification, treatment, and monitoring of breeding sites.
Adult Mosquito Surveillance
The goal of the Fairfax County adult mosquito surveillance program is to monitor adult vector mosquito populations and their West Nile virus infection rates in order to better predict risk to human populations, and to try to determine other associated factors that may influence West Nile virus transmission to humans. The mosquito surveillance program includes trapping stations found throughout the County, where mosquito traps are set on a weekly basis to collect adult mosquitoes. These mosquito traps are a critical element of the County's mosquito-borne disease surveillance program and provide important data for analysis. If you see this equipment, please do not disturb it. Mosquito samples, or pools, are laboratory tested for West Nile virus by reverse-transcriptase polymerase chain reaction (RT-PCR). Mosquito pools can also be tested for LaCrosse Encephalitis and St. Louis Encephalitis by RT-PCR under certain conditions (i.e., when human cases have been reported).
Mosquito Egg Surveillance
The DCIP occasionally collects eggs of certain container-breeding mosquitoes using ovitraps. These traps are useful in detecting some mosquitoes that are not generally collected in traditional adult mosquito traps.
A tick surveillance program was established in collaboration with the Virginia Department of Health in May 2005. The program aims to define areas of public health risk according to tick populations and the diseases that they may transmit. Ticks are collected in Fairfax County using a variety of sampling methods. Collected ticks are identified to species and life stage (larvae, nymph, or adult) before being sent to the lab for pathogen testing.
Human cases of mosquito- and tick-borne diseases are reported to the Health Department through passive and active surveillance activities, which can be found in the Health Department's yearly Communicable Disease Summary Report. The surveillance data are used by the DCIP in assessing public health risk levels.