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Mosquito Prevention & Information

The Vector Borne Illness Prevention Program monitors and works to reduce the mosquito population in Alexandria. We do this to help decrease the incidence of mosquito-borne illnesses. Learn more about mosquitoes, our program and what steps you can take to protect yourself and your family.

Protection and Prevention

Personal Protection 

To prevent mosquito bites:

  • Wear long, loose, and light-colored clothing
  • Choose and use a repellent that contains one of these active ingredients: DEET, Picaridin, oil of lemon eucalyptus, or IR-3535.

Different Types of Repellent

The best repellent is one that you will actually use.

  • DEET-based repellents are available in various concentrations that repel insects equally well for the length of time needed. DEET has provided effective, dependable protection since the 1950s. DEET is the most effective and best-studied repellent available.
  • Picardin is a synthetic repellent developed in the 1990s. It is colorless, nearly odorless, and is available in multiple formulations. It provides long-lasting, effective protection similar to identical concentrations of DEET. 
  • IR-3535 (Merck 3535) is registered as a biopesticide. Approved for use in the USA in 1999, it has been used in Europe for 20 years.
  • Oil of Lemon Eucalyptus is a natural plant-based repellent. Products containing oil of lemon eucalyptus provide protection similar to low concentrations of DEET. Products containing oil of lemon eucalyptus should not to be used on children under the age of three years.

All of these products are available in a wide variety of forms including aerosol and pump sprays, and wipes. For more information on mosquito repellants visit:


Flowerpot Dish Collecting Water
Flower Pot Collecting Water

Bird Bath Collecting Water
Bird Bath Collecting Water

Corrugated Drain Pipe Collecting Water
Corrugated Pipe Collecting Water

Clogged Gutter Collecting Water
Clogged Gutter with water

To get rid of adult mosquitoes around your home, follow these tips.

Once a week

  • Empty water from containers, such as flowerpot saucers, watering cans, and buckets
  • Change the water in bird baths
  • Empty water that collects in the folds of tarps used to cover woodpiles, boats, pools, etc.
  • Position corrugated drainpipes to ensure drainage

Once a month

  • Apply a larvicide (an insecticide applied to water to kill mosquito larvae), such as Mosquito Dunks®, to standing water that cannot be emptied or drained.

As necessary

  • Clean leaves and debris from roof gutters.
  • Recycle old tires
  • Be sure water on property flows freely from drainage areas
  • Fill-in puddles or areas of your yard that remain wet and soggy for more than a week
  • Aerate ornamental ponds or stock the pond with fish
  • Apply a barrier spray to vegetation around your home. Products containing the active ingredient permethrin will provide two to three weeks of relief from biting adult mosquitoes. Always follow label instructions.

Mosquito Identification

Asian Tiger Mosquito. Sean McCann. Copywrite 2006.The Asian Tiger Mosquito (Aedes albopictus) is the number one nuisance species found in the city. It is a black mosquito with striking white markings on its body and legs. The Asian Tiger Mosquito is a very aggressive mosquito that bites during the day. They prefer to bite people, and they lay their eggs in containers like tires, buckets, flowerpots, and corrugated drainpipes that hold water for five or more days. They live where it is cool, humid and shady, and do not travel far from there. Bushes like ivy and azaleas are their favorite resting places. The Asian Tiger Mosquito can spread West Nile virus, but it is unlikely.

Culex Species MosquitoCulex mosquitoes (Culex pipiens and Culex restuans) are small brown mosquitoes that bite during dusk and dawn. They prefer to bite birds, but they will bite people and other mammals. Because they are not as aggressive as other mosquitoes, you may not notice when one is biting you – a good reason to wear insect repellent ! Culex mosquitoes lay eggs in stagnant, organic, nutrient-rich water. These are places like storm drains, clogged rain gutters and sites where water stands for a longer period of time (a few weeks). It is these mosquitoes that are most likely to spread West Nile virus

Mosquito Biology

There are four stages in the life of a mosquito: egg, larva, pupa, and adult. Mosquitoes need standing water to complete their life cycle.

Mosquito Life Cycle
  1. Mosquito eggs are laid so they hatch in water, generally not in moving water or water with aquatic life (fish, frogs)
  2. Larvae feed and grow in the water for about one week
  3. A larva turns into a pupa, which is also found in the water, but does not feed
  4. Inside the pupal case, an adult mosquito develops and transforms into the familiar flying form

Female mosquitoes bite because they need blood to develop their eggs. During the month a female mosquito is alive, she can lay eggs three or four times. Each time she lays eggs, she will lay up to 200-300 eggs.

West Nile Virus

West Nile virus (WNV) is a virus that is spread to people by the bite of an infected mosquito. Symptoms generally appear three to 15 days after being bitten. People with weakened immune systems and people over the age of 50 are at greatest risk for developing complications or illness from the virus. Currently, no vaccine against WNV is available for people.

WNV in Alexandria 

Each year, the Health Department traps and tests mosquitoes for WNV. These traps are located at sites around the City in areas where mosquitoes are found.  West Nile can be found in mosquitoes beginning in July or very early August.  

Mosquito Trap 2  mosquito trap  Mosquito Trap 1 
Adult mosquito traps used in the city.

Transmission Cycle  

West Nile Virus is passed regularly between birds and mosquitoes.

  • An infected bird is bitten by a mosquito
  • The mosquito picks up the virus from the bird
  • The infected mosquito feeds on an uninfected bird; the virus is passed to the bird and the WNV cycle continues.
  • Sometimes, the infected mosquito will feed on humans or horses. Some of these humans and horses can get sick or die from the infection.

WNV Transmission Cycle, Courtesy of the CDC  

Signs and Symptoms 

Symptoms usually appear three to fifteen days after a person is bitten by an infected mosquito. Approximately 80% of people who are infected with WNV will not feel sick.

Mild symptoms: Up to 20% of the people infected with WNV develop WNV fever. Symptoms may include fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach, and/or back. Symptoms may last for a few days to several weeks.

Serious symptoms: About one in 150 people develop severe illness. This may include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, or paralysis. These symptoms may last several weeks and neurological effects may be permanent. West Nile virus infection can be fatal.

What the City Does

Staff checking for mosquitos in storm drain Staff applying pesticide Staff working in lab

The Vector Borne Illness Prevention Program is involved in a number of activities throughout the mosquito season and is responsible for:

  • Trapping adult mosquitoes to monitor mosquito populations
  • Testing the mosquitoes for West Nile virus to estimate the risk of mosquito-borne disease transmission
  • Responding to areas identified as having a higher-risk of disease transmission with increased surveillance, larvicide treatments, and/or community outreach
  • Proactively inspecting and larviciding storm drains. These areas are then recorded and mapped and are regularly treated to kill mosquito larva
  • Providing residents and businesses assistance with mosquito problems
  • Providing education and information at various local events and festivals to promote effective mosquito control
  • Giving presentations for various civic associations and communities
  • Investigating complaints about mosquitoes made by local residents

Contact Us

Vector-Borne Illness Prevention Program
Alexandria Health Department  
4480 King Street, 3rd Floor
Alexandria, VA 22302

Phone: 703.746.4910
Hours: 8 a.m. to 4:30 p.m. (M,Tu,W,F) and 1:30 p.m. to 4:30 p.m. (Th)