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Zika Virus

Zika virus is primarily transmitted by the bite of an infected mosquito (Aedes aegypti and Aedes albopictus), which are aggressive daytime biters (but they also can bite at night). These mosquitoes also serve as competent vectors of the Dengue, Chikungunya, Yellow Fever viruses, and other arboviral diseases. Zika can also be transmitted during sex (without a barrier method) with a partner who lives in or traveled to an area with Zika and from a pregnant woman to her developing fetus. Zika virus infection during pregnancy can cause microcephaly and other severe fetal brain defects. Other problems with pregnancies have been documented before birth including: miscarriages, stillbirth, brain structure abnormalities, and defects of the eye, hearing deficits and impaired growth. Differential diagnosis for Zika virus disease may include both Dengue and Chikungunya.

In May 2015, Zika virus started circulating in the Western Hemisphere; prior to 2015 Zika outbreaks were documented in areas of Africa, Southeast Asia and the Pacific Islands. The first locally-acquired case in the Americas was reported in Brazil. Now, local transmission of Zika been reported in Mexico, the Caribbean, Central America, South America and some South Pacific Islands along with three US territories (Puerto Rico, US Virgin Islands and America Samoa). Majority of Zika cases in the US are travel-associated (or imported). As of August 2016, the first local transmission of Zika virus has been reported in the continental US. The Florida Department of Health has identified a one-square-mile area within the Wynwood neighborhood of Miami where Zika is spreading by mosquitoes. To date, residents of Miami-Dade, Broward, and Palm Beach counties have been infected with the Virus. Pregnant women are advised not to travel to the affected area, or if they live or work in this area, to consistently follow steps to prevent mosquito bites and sexual transmission of Zika virus. Pregnant women who traveled to this area on or after June 15, 2016, are advised to talk with their healthcare provider and be tested for Zika infection. Areas with active Zika virus transmission continue to change.

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Dengue has emerged as a worldwide health problem. Locally transmitted Dengue rarely occurs in the United States; however, it is endemic in United States territories such as, Puerto Rico and other travel destinations in Latin America, Southeast Asia and the Pacific islands. The principal symptoms of dengue are high fever and at least two of the following: severe headache, severe eye pain (behind eyes), joint pain, muscle and/or bone pain, rash, mild bleeding manifestation (e.g., nose or gum bleed, petechiae, or easy bruising), or low white cell count. Generally, younger children and those with their first dengue infection have a milder illness than older children and adults. There is no specific medication for treatment of a dengue infection. Persons who think they have dengue should use analgesics (pain relievers) with acetaminophen and avoid those containing ibuprofen, Naproxen, aspirin or aspirin containing drugs. They should also rest, drink plenty of fluids to prevent dehydration, avoid mosquito bites while febrile and consult a physician. (CDC)

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Chikungunya Virus

Chikungunya outbreaks have occurred in countries in Africa, Asia, Europe, and the Indian and Pacific Oceans. In late 2013, chikungunya virus was found for the first time in the Americas on islands in the Caribbean. As of August 2016, all reported cases reported in the U.S. occurred in travelers returning from affected areas. No locally-transmitted cases have been reported from U.S. states. The most common symptoms of chikungunya virus infection are fever and joint pain. Other symptoms may include headache, muscle pain, joint swelling, or rash. There is currently no vaccine to prevent or medicine to treat chikungunya virus.

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As of July 2016, suspect Dengue virus disease (Dengue), Chikungunya virus disease (Chikungunya), Zika virus disease (Zika) and Zika virus congenital infection are mandated reports to local Public Health (CCR §2500). Please refer to full list of reportable communicable diseases.

  1. Report any suspect or laboratory-confirmed case of Zika, Dengue or Chikungunya (Title 17, California Code of Regulations (CCR) §2500).
  2. Obtain History: a complete travel and medical history including:
    • Travel details including: locations (country and state) and dates,
    • Symptoms and onset date,
    • Mosquito exposure and mosquito bite information,
    • Any additional possible exposure,
    • Close contact with similar symptoms or clinical diagnosis
    • Pregnancy status (with estimated delivery date)


Zika virus testing is available through Contra Costa Public Health Laboratory by completing the Zika Case History Form and Laboratory Requisition Slip. Regarding specific information on Zika specimen submittal please refer to the posted health advisory. For additional assistance with submittal call Contra Costa Public Health Laboratory at 925-370-5775.
Remember to submit specimens with a completed Zika Case Report Form.

Zika Virus
Dengue & Chikungunya

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