Zika virus disease (Zika) is a disease caused by the Zika virus, which is spread to people primarily through the bite of an infected Aedes species mosquito. The most common symptoms of Zika are fever, rash, joint pain, and conjunctivitis (red eyes). The illness is usually mild with symptoms lasting for several days to a week after being bitten by an infected mosquito. People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. For this reason, many people might not realize they have been infected. However, Zika virus infection during pregnancy can cause a serious birth defect called microcephaly, as well as other severe fetal brain defects. Once a person has been infected, he or she is likely to be protected from future infections.
Zika virus was first discovered in 1947 and is named after the Zika Forest in Uganda. In 1952, the first human cases of Zika were detected and since then, outbreaks of Zika have been reported in tropical Africa, Southeast Asia, and the Pacific Islands. Zika outbreaks have probably occurred in many locations. Before 2007, at least 14 cases of Zika had been documented, although other cases were likely to have occurred and were not reported. Because the symptoms of Zika are similar to those of many other diseases, many cases may not have been recognized.
In May 2015, the Pan American Health Organization (PAHO) issued an alert regarding the first confirmed Zika virus infection in Brazil. On February 1, 2016, the World Health Organization (WHO) declared Zika virus a Public Health Emergency of International Concern (PHEIC). Local transmission has been reported in many other countries and territories. Zika virus will likely continue to spread to new areas.
Specific areas whereZika is spreading are often difficult to determine and are likely to change over time. If traveling, please visi the CDC Travelers’ Health site for the most updated travel information.
What we know
- No vaccine exists to prevent Zika virus disease (Zika).
- Prevent Zika by avoiding mosquito bites (see below).
- Mosquitoes that spread Zika virus bite mostly during the daytime.
- Mosquitoes that spread Zika virus also spread dengue and chikungunya viruses.
- Prevent sexual transmission of Zika by using condoms or not having sex
Steps to prevent mosquito bites
When in areas with Zika and other diseases spread by mosquitoes, take the following steps:
- Wear long-sleeved shirts and long pants.
- Stay in places with air conditioning and window and door screens to keep mosquitoes outside.
- Sleep under a mosquito bed net if you are overseas or outside and are not able to protect yourself from mosquito bites.
- Use Environmental Protection Agency (EPA)-registered insect repellents with one of the following active ingredients: DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol. Choosing an EPA-registered repellent ensures the EPA has evaluated the product for effectiveness. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breast-feeding women.
- Always follow the product label instructions.
- Reapply insect repellent as directed.
- Do not spray repellent on the skin under clothing.
- If you are also using sunscreen, apply sunscreen before applying insect repellent.
- To protect your child from mosquito bites:
- Do not use insect repellent on babies younger than 2 months old.
- Do not use products containing oil of lemon eucalyptus or para-menthane-diol on children younger than 3 years old.
- Dress your child in clothing that covers arms and legs.
- Cover crib, stroller, and baby carrier with mosquito netting.
- Do not apply insect repellent onto a child’s hands, eyes, mouth, and cut or irritated skin.
- Adults: Spray insect repellent onto your hands and then apply to a child’s face.
- Treat clothing and gear with permethrin or purchase permethrin-treated items.
- Treated clothing remains protective after multiple washings. See product information to learn how long the protection will last.
- If treating items yourself, follow the product instructions carefully.
- Do NOT use permethrin products directly on skin. They are intended to treat clothing.
Even if they do not feel sick, travelers returning to the United States from an area with Zika should take steps to prevent mosquito bites for 3 weeks so they do not spread Zika to mosquitoes that could spread the virus to other people.
Through mosquito bites
Zika virus is transmitted to people primarily through the bite of an infected Aedes species mosquito (A. aegypti and A. albopictus). These are the same mosquitoes that spread dengue and chikungunya viruses.
- These mosquitoes typically lay eggs in and near standing water in things like buckets, bowls, animal dishes, flower pots and vases. They prefer to bite people, and live indoors and outdoors near people.
- Mosquitoes that spread chikungunya, dengue, and Zika are aggressive daytime biters. They can also bite at night.
- Mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites.
From mother to child
- A pregnant woman can pass Zika virus to her fetus during pregnancy. Zika is a cause of microcephaly and other severe fetal brain defects, and we are studying the full range of other potential health problems that Zika virus infection during pregnancy may cause.
- A pregnant woman already infected with Zika virus near the time of delivery can pass on the virus to her newborn around the time of birth.
- To date, there are no reports of infants getting Zika virus through breastfeeding. Because of the benefits of breastfeeding, mothers are encouraged to breastfeed even in areas where Zika virus is found.
Through sexual contact
- Zika virus can be spread by a man to his sex partners.
- In known cases of sexual transmission, the men developed Zika virus symptoms. From these cases, we know the virus can be spread when the man has symptoms, before symptoms start and after symptoms resolve.
- In one case, the virus was spread a few days before symptoms developed.
- The virus is present in semen longer than in blood.
Through blood transfusion
- As of February, 1, 2016, there have not been any confirmed blood transfusion transmission cases in the United States.
- There have been multiple reports of blood transfusion transmission cases in Brazil. These reports are currently being investigated.
- During the French Polynesian outbreak, 2.8% of blood donors tested positive for Zika and in previous outbreaks, the virus has been found in blood donors.
- Anyone who lives in or travels to an area where Zika virus is found and has not already been infected with Zika virus can get it from mosquito bites. Once a person has been infected, he or she is likely to be protected from future infections.
- Traveling? Visit CDC’s Travelers Health website to see if the country you plan to visit has any travel health notices.
- Even if they do not feel sick, travelers returning to the United States from an area with Zika should take steps to prevent mosquito bites for 3 weeks so they do not spread Zika to mosquitoes that could spread the virus to other people.
- CDC has posted maps that show elevation levels in countries with Zika.
- Mosquito Bite Prevention for Travelers [PDF – 2 pages]
- Read the Traveler’s Health Yellow Book for more information on Protection against Mosquitoes, Ticks, Fleas & Other Insects and Arthropods.
- Most people infected with Zika virus won’t even know they have the disease because they won’t have symptoms. The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week.
- See your healthcare provider if you are pregnant and develop a fever, rash, joint pain, or red eyes within 2 weeks after traveling to a place where Zika has been reported. Be sure to tell your health care provider where you traveled.
- The illness is usually mild with symptoms lasting for several days to a week after being bitten by an infected mosquito.
- People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. For this reason, many people might not realize they have been infected.
- Zika virus usually remains in the blood of an infected person for about a week but it can be found longer in some people.
- Once a person has been infected, he or she is likely to be protected from future infections.
- The symptoms of Zika are similar to those of dengue and chikungunya, diseases spread through the same mosquitoes that transmit Zika.
- See your healthcare provider if you develop the symptoms described above and have visited an area where Zika is found.
- If you have recently traveled, tell your healthcare provider when and where you traveled.
- Your healthcare provider may order blood tests to look for Zika or other similar viruses like dengue or chikungunya.
- There is no vaccine to prevent or medicine to treat Zika virus.
- Treat the symptoms:
- Get plenty of rest.
- Drink fluids to prevent dehydration.
- Take medicine such as acetaminophen (Tylenol®) or paracetamol to reduce fever and pain.
- Do not take aspirin and other non-steroidal anti-inflammatory drugs (NSAIDS) until dengue can be ruled out to reduce the risk of bleeding.
- If you are taking medicine for another medical condition, talk to your healthcare provider before taking additional medication.
- If you have Zika, prevent mosquito bites for the first week of your illness.
- During the first week of infection, Zika virus can be found in the blood and passed from an infected person to a mosquito through mosquito bites.
- An infected mosquito can then spread the virus to other people.
- UPDATE: Interim Guidance for Prevention of Sexual Transmission of Zika Virus – United States, 2016 (March 25, 2016)
- MMWR: Transmission of Zika Virus Through Sexual Contact with Travelers to Areas of Ongoing Transmission — Continental United States, 2016
- Interim Guidelines for Prevention of Sexual Transmission of Zika Virus – United States, 2016
- Zika and Sexual Transmission (Feb. 12, 2016)
- Questions and Answers on Zika and Sexual Transmission
- Mosquito Life-Cycle
- Mosquitoes’ Main Aquatic Habitats
- Help Control Mosquitoes that Spread Dengue, Chikungunya, and Zika Viruses[PDF – 2 pages] (English)
- Help Control Mosquitoes that Spread Dengue, Chikungunya, and Zika Viruses[PDF – 2 pages] (Spanish)
- Prevent Mosquito Production in your Septic Tank[PDF – 1 page]
- MMWR Zika Reports
- Health Alert Network- Update: Interim Guidelines for Prevention of Sexual Transmission of Zika Virus — United States, 2016
- Zika Travel Health Information
- Zika Virus Health Information Resource Guide (NIH Disaster Information Management Research Center)
- Zika virus in Brazil (May 7,2015) (Pan American Health Organization)
- Zika virus infection (European Centre for Disease Prevention and Control)
- Zika virus (New Zealand Ministry of Health)
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For Vector Control Professionals
- EID Zika Spotlight
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