Mosquitoes are present in San Diego, a fact that often surprises newcomers given the region’s mild climate. While celebrated for its sunny beaches and diverse landscapes, the area is not immune to these insects. Mosquitoes are a nuisance and introduce public health concerns due to disease transmission. Understanding the local mosquito population and how to manage it is important for residents and visitors.
Common Mosquito Species in San Diego
San Diego County is home to several mosquito species, some posing a greater public health concern. Native Culex species, such as Culex quinquefasciatus (Southern House Mosquito) and Culex tarsalis (Western Encephalitis Mosquito), are active from dusk through dawn. They lay eggs in stagnant water sources like neglected swimming pools, storm drains, and natural standing water. Culex tarsalis is slightly larger than Aedes species.
Invasive Aedes mosquitoes, including Aedes aegypti (yellow fever mosquito) and Aedes albopictus (Asian tiger mosquito), have also been introduced. These “ankle biter” mosquitoes are small, black with white stripes on their legs and backs, and bite aggressively during the day. Unlike native mosquitoes, Aedes species primarily breed in small containers of standing water in urban and suburban areas, and their eggs can survive dry conditions for months.
Diseases Transmitted by Mosquitoes
Mosquitoes in San Diego have the capacity to transmit several diseases, with West Nile Virus (WNV) being the most commonly observed mosquito-borne illness in the area. Culex species mosquitoes transmit WNV after feeding on infected birds, which are the primary hosts for the virus. Most people infected with WNV experience no symptoms, but about one in five may develop mild, flu-like symptoms such as fever, headache, body aches, joint pain, vomiting, or a rash. In rare instances, approximately 1 in 150 infected individuals can develop severe neurological conditions like encephalitis or meningitis, characterized by high fever, neck stiffness, disorientation, tremors, or paralysis.
While not endemic to San Diego, invasive Aedes mosquitoes present a potential risk for the local transmission of diseases such as Zika, Dengue, and Chikungunya viruses. These viruses are typically acquired by travelers visiting regions where the diseases are common. If an Aedes mosquito in San Diego bites an infected traveler, it can then transmit the virus to other people in the area. Symptoms for these diseases often include fever, headache, and muscle or joint pain, with Dengue also potentially causing eye pain and rash, and Chikungunya known for more pronounced joint pain. Public health agencies in San Diego actively monitor mosquito populations and disease activity to mitigate these risks.
Protecting Yourself and Your Property
Residents can take several steps to protect themselves and their properties from mosquitoes. Personal protection involves using EPA-registered insect repellents with active ingredients like DEET, picaridin, oil of lemon eucalyptus, or IR3535 when outdoors. Wearing long-sleeved shirts and long pants, especially during peak mosquito activity or when Aedes mosquitoes are active, provides a physical barrier against bites. Ensuring window and door screens are in good condition and properly secured helps prevent mosquitoes from entering homes.
Managing your property to eliminate mosquito breeding sites is equally important. Mosquitoes lay eggs in standing water; even a small amount, like a quarter-inch, is enough for reproduction. Regularly inspect and empty containers that can hold water, including plant saucers, buckets, old tires, and children’s toys, at least once a week. Cleaning rain gutters to prevent water accumulation and maintaining swimming pools are also effective measures. The San Diego County Vector Control Program supports community efforts through surveillance, public education, and providing free mosquito fish for water features that cannot be drained, such as ponds.