West Nile virus is a Flavivirus spread by certain species of mosquitoes. It is the most predominant mosquito borne disease in California, and is endemic in the state, which means it’s always present in the environment as it cycles between mosquitoes and a wide variety of bird species. Humans and other animals like horses are also susceptible but do not contribute to the disease cycle.

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

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…

Flea-borne typhus (typhus) is caused by the bacteria Rickettsia typhi and Rickettsia felis.  These bacteria are transmitted by the bite of cat fleas (Ctenocephalides felis) or rat fleas (Xenopsylla cheopis) which are found on many vertebrate hosts including opossums, rats, mice, and cats.  Fleas that feed on infected animals can become infected and transfer the bacteria to eggs containing their…