Mosquitoes are present across Washington State, becoming active during warmer months. Their presence is a common seasonal occurrence, influencing outdoor activities from late spring through early fall.
Mosquito Species in Washington
Washington State is home to over 40 mosquito species. Common types include the Northern House mosquito (Culex pipiens), the Western Encephalitis mosquito (Culex tarsalis), and Aedes vexans. Female mosquitoes require a blood meal for egg development. Most species are active during dawn and dusk.
Geographic Distribution and Habitats
Mosquitoes are widespread throughout Washington State, thriving in environments with standing water for breeding. They are common in wetlands, irrigated agricultural areas, and urban settings where water can collect. Higher mosquito populations, particularly those carrying West Nile Virus, are often detected in south-central Washington. Western Washington’s wet climate and temperatures also contribute to robust populations.
Mosquito-Borne Diseases
Mosquitoes in Washington State can transmit several diseases, with West Nile Virus (WNV) being the primary concern. WNV has been detected annually in the state since 2002. Most people infected with WNV experience no symptoms, but about one in five develop fever, headache, body aches, or a rash. In rare instances, WNV can lead to severe neurological conditions like encephalitis. Historically, Western Equine Encephalitis and St. Louis Encephalitis have also caused outbreaks in the state.
Other diseases like Zika and Dengue are not transmitted locally in Washington. The mosquito species responsible for spreading Zika and Dengue, Aedes aegypti and Aedes albopictus, are not established in the state. Any cases reported in Washington residents are associated with travel to affected regions. Public health focuses on monitoring and preventing WNV spread.
Personal Protection and Control
Protecting against mosquito bites involves several steps. Use EPA-registered insect repellents containing DEET, picaridin, or oil of lemon eucalyptus. Wear long-sleeved shirts, long pants, and hats outdoors, especially during peak activity at dawn and dusk. Ensure window and door screens are in good repair to prevent mosquitoes from entering homes.
Controlling mosquito populations around the home involves eliminating standing water sources. Even small amounts of stagnant water in containers like old tires, buckets, and flowerpot saucers can serve as breeding grounds. Cleaning clogged roof gutters and fixing leaky outdoor faucets or sprinklers also prevent water accumulation. Maintaining trimmed lawns and vegetation can reduce resting areas for adult mosquitoes.