Zika Virus

What is Zika virus?

Zika is a virus spread by mosquitoes. It was first discovered in the Zika Forest of Uganda in 1947. For many decades, it was thought to be a rare cause of viral infection. It was found only in small areas of Africa, the Yap Islands in the Pacific, and Easter Island. But in April 2015, it was found in Brazil. It then spread quickly to many countries in South America and Central America, and to the Caribbean and Mexico. The number of cases in these areas has gone down a lot since then.

Zika cases were also found in the U.S. during the height of the 2015 outbreak. Most of these people got the virus while visiting other parts of the world where mosquitoes were spreading it. But in some cases the virus had been spread by mosquitoes in the U.S.

What causes Zika virus?

The Zika virus is mostly passed on by the bite of the mosquito species Aedes. Pregnant people who have it can also pass it on to their unborn child. People may also get it through sexual contact and blood transfusion or organ transplantation. 

What are the symptoms of Zika virus?

The time it takes from exposure to the Zika virus to the appearance of symptoms (called the incubation period) is not known for sure. But it's believed to be a few days. Most people infected with the Zika virus have no symptoms. For the 1 out of 5 people who do have symptoms, they are often very mild. They last 2 to 7 days and then go away completely. They may include:

  • Fever

  • Rash

  • Extreme tiredness (fatigue)

  • Headache

  • Joint and muscle pain

  • Conjunctivitis, when the eyes become red, irritated, and inflamed

How is Zika virus diagnosed?

Blood or other bodily fluids such as urine or semen testing can detect the Zika virus. Pregnant people who live in or have traveled to areas where the virus is active, or who are sexually active without a condom with someone who lives in or traveled to a Zika area, should talk with their healthcare provider about whether they should be tested. More testing may be needed to check on the health of the unborn child, or the health of a newborn whose birth parent has recently traveled to those areas. Anyone who is not pregnant but may have been exposed to the Zika virus, or has current or recent symptoms of Zika, should also be tested.

Experts update information weekly on who should be tested. Check the CDC website for the latest advice.

How is Zika virus treated?

There is no medicine to cure the Zika virus. Treatment is aimed at easing symptoms. Rest and drinking plenty of fluids are helpful. Acetaminophen can help ease fever and pain.

What are possible complications of Zika virus?

For pregnant people, Zika can be a serious concern. A pregnant person can pass the virus on to the unborn child. This is true even if the pregnant person has no symptoms. The virus can cause a condition called microcephaly in these infants. Babies with this serious birth defect are born with a smaller than normal head size and a less developed brain. Babies can have a range of problems depending on how severe their microcephaly is. They may have developmental and neurological problems; learning disabilities; vision, hearing, and swallowing problems; or seizures. These risks have led the CDC to issue recommendations that pregnant people not travel to areas with active Zika virus transmission.

If you want to become pregnant in the near future, but you or your partner live in or traveled to an area with a Zika outbreak or an area with risk of Zika infection, talk with your healthcare provider about your planned pregnancy.

The Zika virus may also very rarely cause Guillain-Barré syndrome (GBS) in adults. GBS causes muscle weakness or paralysis. If the muscle weakness is severe enough or widespread enough, the person may need to use a machine to breathe (ventilator). Most people with GBS recover. Recovery may take as little as a few weeks or as long as a few years. Sometimes recovery is not complete. Researchers are looking more closely at the possible link between Zika and GBS.

What can I do to prevent Zika virus?

Zika can be prevented in the same way as other mosquito-borne diseases. That means taking steps to protect against mosquito bites:

  • Wear long-sleeved shirts and pants when outdoors in areas where mosquitoes are active.

  • Put on insect repellent before going outdoors.

  • Use air conditioning or screens on doors and windows to keep mosquitoes out of your home.

  • Empty water from any containers so mosquitoes have fewer places to breed. Even small items like bottle caps can hold enough water for mosquitoes to multiply.

  • Don’t travel to places where there is a Zika outbreak, especially if you are pregnant or plan to become pregnant.

  • If you have traveled to an area where Zika is found, or you have already been infected with the virus, practice safe sex. Use a condom for at least 6 months so that you don’t spread the virus.

  • Zika virus infections are new—at least in their current widespread form. If you plan to travel to places with known Zika outbreaks, get the latest travel recommendations from the CDC website or the World Health Organization (WHO) website before you go.

Key points about Zika virus

  • Zika is a virus spread by mosquitoes.

  • In 2015, the virus spread quickly to many countries in South America and Central America, the Caribbean, and Mexico. But cases have recently decreased. Many cases were also found in the U.S. at the height of the Zika outbreak.

  • The Zika virus is mostly passed on by the bite of the mosquito species Aedes. People may also get it through sexual contact and blood transfusion.

  • A pregnant person can pass the virus on to the unborn child, even without symptoms. The virus can cause a birth defect called microcephaly.

  • There is no medicine to cure the Zika virus. Treatment is aimed at easing symptoms.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your provider if you have questions.

Online Medical Reviewer: Barry Zingman MD
Online Medical Reviewer: L Renee Watson MSN RN
Online Medical Reviewer: Marianne Fraser MSN RN
Date Last Reviewed: 9/1/2021
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