Vector-borne Disease

What is a Vector-Borne Disease?

Vector-borne diseases are infections transmitted to humans and animals through blood-feeding arthropods like mosquitoes, ticks, and fleas. Common examples include Dengue fever, West Nile Virus, Zika, and typhus.

Mosquito on skin with text about vector-borne diseases transmitted by mosquitoes, ticks, or fleas.

In Los Angeles County, West Nile virus (WNV) remains the most significant vector-borne disease threat. As an endemic virus in California, it resurfaces annually and spreads once it reaches the human population.

Tropical diseases, such as dengue fever, are traditionally linked to international travel to regions where these diseases are endemic. However, with the establishment of Aedes Mosquitoes (Ankle Biters)—the primary carrier of dengue—in California, local transmission is now a growing concern. The Los Angeles County Department of Public Health confirmed 14 locally acquired dengue cases in 2024.

This is why vector control urges residents to take action: TIP out stagnant water, TOSS unused containers that can collect water, and PROTECT yourself with mosquito repellent. Community participation, alongside vector control efforts, is essential to lowering mosquito populations and protecting against vector-borne diseases.

West Nile Virus

Mosquitoes spread West Nile virus (WNV) when they bite birds and people. The mosquito species that can transmit West Nile virus are native to Los Angeles County.

Microscopic view of viral particles with green clusters on a pink background.

Dengue Fever

Dengue virus (DENV) is a mosquito-borne virus that can cause mild to severe acute febrile illness in humans. It is now endemic year round in most countries in the tropics and sub tropics. Dengue fever can progress to dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), which are potentially life-threatening. Cases of dengue fever often experience a sudden onset of fever greater than 101…

Microscopic image of a cluster of blue-tinted virus particles with a hexagonal arrangement.

Chikungunya

Chikungunya virus is transmitted to people by two species of mosquitoes, Aedes aegypti and Aedes albopictus (also known as invasive Aedes or ankle biters). Both species are found in Los Angeles County.

Microscopic view of viruses, with red viral particles scattered across a purple background.

Zika Virus

Zika is spread mostly by the bite of the invasive Aedes species mosquitoes. These mosquitoes bite primarily during the day, indoors and outdoors.

A magnified image of a flea, showing detailed structure and legs.

Fleas and Flea-borne Typhus

Flea-borne (murine) typhus, is a disease caused by a bacteria called Rickettsia typhi. Flea-borne typhus is spread to people through contact with infected fleas. Fleas become infected when they bite infected animals, such as rats, cats, or opossums.

Dengue in the San Gabriel Valley

Read the latest information regarding Dengue in the San Gabriel Valley.

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About Repellents

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