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Zika in Humans

Zika disease in humans is caused by infection with the Zika virus which is transmitted most often by the bite of an infected mosquito

See also the EDEN Zika Virus and Vectors page for more information.

Note: The Use Permission for the information and images made available on this page extend to all EDEN member Extension programs.


Transmission and Symptoms 

Most people who are infected with the virus do not get sick. For those who do become ill, the symptoms that have been reported include fever, rash, joint pain, and conjunctivitis.Death from Zika infection is extremely rare. Complications can arise for pregnant women who are infected with Zika virus. The US CDC provides details and recommendations for pregnant women. http://www.cdc.gov/media/releases/2016/s0413-zika-microcephaly.html

The primary mode of transmission of Zika is from the bite of infected Aedes mosquitoes. There is evidence of transmission of Zika virus through sexual contact, from mother to child, and blood transfusions (http://www.cdc.gov/zika/transmission/).

 

 

Graphic of Zika Disease symptoms
Symptoms of ZIka virus infection. Credit: Pan American Health Organization and World Health Organization. (public domain). Click for larger image.


"Imported" Cases of Zika 

Imported cases of Zika are defined as those that occur when a person has travelled to an area where the virus is cycling among mosquitoes and the human population and contracted the disease there. Upon returning home, the person may become ill and visit a physician. If testing shows that they do have an infection with Zika virus, the case would be considered “imported” because they contracted the pathogen abroad, but are diagnosed in the US. For example, if you travel to Brazil and were bitten by an infected mosquito in Brazil, but were diagnosed with Zika virus in the US, then you would be considered an imported case.

Graphic on Imported Cases of Mosquito-Borne Disease
“Imported” cases of mosquito-borne diseases. Credit: CDC (public domain). Click for larger image.


"Local" cases of Zika 

Local transmission of Zika virus means that the virus is circulating in mosquitoes found within the US, and that humans are infected when bitten by mosquitoes in their community. For example, if an infected mosquito bit you in your backyard and you were diagnosed with Zika virus, then you would be considered a local case. As of this writing (April 2016), the only cases of Zika that have been reported in the continental United States have been imported cases http://www.cdc.gov/zika/geo/united-states.html

Local transmission of the virus is occurring in the following territories of the United States: American Samoa, Puerto Rico, Marshall Islands, and the US Virgin Islands (St. Croix, St. Thomas, and St. John). For up-to-date information on areas with local transmission, visit: http://www.cdc.gov/zika/geo/index.html

Graphic of Local Zika Disease cases
“Local” cases of mosquito-borne diseases. Credit: CDC (public domain) Click for larger image.


Risk for the United States 

Cases of Zika that are imported into the United States have the potential to contribute to local transmission. There is a period of about 14 days after being infected when mosquitoes can pick up the virus from humans. If someone with an infection is exposed to local Aedes mosquito vectors, the virus could then be picked up and transmitted by the local mosquito population. Areas with the highest risk of this occurring are those where populations of Aedes aegypti and Aedes albopictus occur. Many states are currently conducting mosquito surveys and updates on the distribution maps are expected.

On July 29, 2016, Florida Rick Scott reported 4 cases of locally acquired Zika in Miami-Dade and Broward Counties. Blood donation centers in Miami-Dade and Broward counties have stoped accepting blood from donors in the affected area until methods to screen blood or techniques to deactivate the virus in blood are put in place. Surveillance of human cases and mosquito texting is on-going and new information will be posted as it is released.

Distribution of Zika Vector Mosquitoes
Estimated range of Zika vectors in the US. Credit: CDC (Public domain). Click for larger image.


Reducing Risk 

Travel

To reduce the risk of infection with Zika virus, travelers should consult the Centers for Disease Control (CDC) website for information on where active, local transmission is on-going http://wwwnc.cdc.gov/travel/page/zika-information. If travel is planned to an area where local transmission has been reported, then CDC guidelines should be followed regarding the use of insect repellents, bed nets, and protective clothing. The recommendations are included at the link shown above.

Pregnant women

Information regarding the Zika virus for pregnant women and women considering pregnancy can be found here: http://www.cdc.gov/zika/pregnancy/index.html



Effective and Ineffective Methods 

There are many items on the market that make claims to repel mosquitoes or to eliminate mosquitoes from an area. Some items that will not offer protection from mosquito bites, or eliminate populations of mosquitoes includes mosquito repellent bracelets, necklaces and other jewelry; mosquito patches; bug zappers; consumption of vitamins; ultrasonic frequency-emitting devices; and homemade mosquito traps. The best protection from mosquito bites is to wear effective mosquito repellents. For details on selecting appropriate repellents, consult this EPA website: https://www.epa.gov/insect-repellents/find-insect-repellent-right-you.

Read also about controlling virus exposure by controlling the mosquito vector on this EDEN Zika Virus and Vectors page.

Photo of bracelet
Example of products that do not provide protection from mosquito bites. James Newman, University of Florida, Florida Medical Entomology Laboratory. Used with permission. Click for larger image.



Last Updated:7/29/2016 10:43 PM
 

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