Zika virus

Zika virus is a type of flavivirus. It belongs to the family of other mosquito-borne viruses that cause illnesses like West Nile fever, dengue, urban yellow fever, and chikungunya.

Zika virus is mostly spread through the bite of infected Aedes mosquitoes (Aedes aegypti and Aedes albopictus). This type of mosquito is found in many countries (including the United States) and tends to bite during daylight hours.

Zika virus was first identified in 1947. It was found in a Rhesus macaque monkey in the Zika Forest in Uganda, a country in East Africa. In the 1950s, evidence of disease in humans was found in other African countries. Infections in humans continued sporadically in parts of Africa and Asia over the next several decades.

Many people in the U.S. first learned of Zika virus during the outbreaks that occurred in the Caribbean and Central and South America from 2014 to 2016. Zika infections were also reported in Florida and Texas. Most of these infections were acquired by people who had traveled to other countries where Zika was prevalent. Nearly 5,800 infections occurred in the U.S. between 2015 and 2017.

Overall, Zika virus is uncommon. No cases of Zika virus transmission from mosquitoes have been reported in the continental U.S. since 2019. Zika infections occur at low rates in other parts of the world, including Central and South America.

Zika virus disease rarely causes hospitalization or death. In most cases, the illness resolves on its own within a week or so. Many people who contract Zika never realize they carry the virus. Serious complications such as brain health issues and severe birth defects occur in rare cases.

What are the types of Zika virus?

There are two main types of Zika virus:  

• African lineage Zika virus, which originated in Uganda.
• Asian lineage Zika virus, which originated in Asia and was responsible for a series of outbreaks in the Americas that began in 2014. It’s also linked to higher rates of congenital differences in newborns and neurological complications.

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Around one in five people with Zika virus disease develop symptoms. Common symptoms of Zika include:

• Fever
• Skin rash, which may be itchy and have both raised and flat areas
• Joint pain
• Muscle pain
• Headache
• Conjunctivitis (pink eye)  
• Pain behind the eyes

Most people who experience symptoms of Zika virus disease begin to feel sick around three to 14 days after infection with the virus. Symptoms are typically mild and last between two and seven days. People with or without symptoms can spread Zika virus to others (through sexual contact or pregnancy) at any point during the course of the infection.

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Although uncommon, Zika virus infection can lead to health complications. These include:

Congenital differences in babies

A pregnant woman or person assigned female at birth can pass Zika virus to a developing fetus. This is known as a congenital Zika infection.

Congenital differences may occur in babies with congenital Zika infections. According to the Centers for Disease Control and Prevention (CDC), around 5 percent of babies born to people who developed Zika virus disease during pregnancy have Zika-related health issues. In some cases, miscarriage, stillbirth, or preterm birth may occur.  

Pregnant people who become infected with Zika virus early in pregnancy have the highest risk of giving birth to a baby with congenital differences. The risk of Zika-related congenital issues is roughly 8 percent when they occur during the first trimester, 6 percent during the second trimester, and about 4 percent during the third trimester.

The most common congenital differences associated with Zika virus include:

• A smaller-than-usual skull size (microcephaly), which can affect brain development
• Reduced coordination and trouble controlling muscles (cerebral palsy)
• Fluid buildup in the brain (hydrocephalus)
• A lack of brain folds (lissencephaly or smooth brain, which can lead to cognitive development issues) 
• Missing parts of the brain
• Intellectual disability
• Severe defects of the brain and spine that occur early in pregnancy (neural tube defects)
• Difficulty swallowing
• Low birth weight
• Reduced joint movement (contractures)
• Seizures
• Issues with hearing or vision

Having a certain combination of Zika-related congenital differences is known as congenital Zika syndrome. This includes severe microcephaly, eye damage, reduced brain tissue, a partially collapsed skull, excess muscle tone (hypertonia), and joint issues.  

If you test positive for Zika virus during pregnancy, a healthcare provider (HCP) will carefully monitor your health and the health of your fetus. This HCP may be an obstetrician (a medical doctor who specializes in pregnancy and childbirth) or a maternal-fetal medicine specialist (an obstetrician who specializes in high-risk pregnancies).

Some babies born to people with Zika virus disease appear healthy at birth but display signs of conditions like microcephaly as they grow older. Because of this, regular health screenings are recommended for babies with congenital Zika infections.   

Zika virus infection during one pregnancy isn’t associated with complications or congenital differences in future pregnancies and babies.

Some of the congenital differences associated with Zika virus require a lifetime of specialized medical care. To learn more about congenital Zika virus infections and how they may be treated or managed, speak with your HCP. You can also browse resources for families with children who have special needs on the CDC website.

Guillain-Barré syndrome

Around 2 in 10,000 people with Zika virus experience Guillain-Barré syndrome (GBS). GBS causes the body’s immune system (the network of organs and cells that guard against infections) to attack its own nerve cells. (When the immune system malfunctions in this way, it’s known as an autoimmune disorder.) GBS can result in muscle weakness or paralysis (loss of muscle function) that may last for several weeks or months.

Many people with Guillain-Barré syndrome make full recoveries with treatment. Permanent muscle damage or death from Zika-related GBS is rare.

Other complications

Especially rare complications of Zika virus infection include: 

• Inflammation and swelling in the spinal cord, the tissues surrounding the brain and spinal cord, or the brain itself. (These conditions are known as myelitis, meningitis, and encephalitis, respectively.)
• A blood disorder that can cause excess bruising, bleeding, or slowed blood clotting (thrombocytopenia)
• Eye inflammation (uveitis)

Zika virus disease is a relatively new condition with many aspects that are still unknown. Researchers are working to learn more about the possible complications of Zika and how to prevent them.

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Zika virus is spread in several ways, including through:

Mosquito bites

Zika virus is most often transmitted through the bite of an infected Aedes mosquito. This type of mosquito is relatively common in the U.S., especially in the Southeast. Aedes mosquito breeding sites include areas of standing water. These may be found in drainage ditches, decorative ponds, bird baths, roof gutters, and dog bowls, as well as lakes and ponds. These mosquitoes are known to bite during the day, though they can also bite at night.  

It's also possible for an uninfected mosquito to acquire Zika virus from an infected person after the mosquito bites them. This mosquito can then spread the virus to other people.

Sexual activity

Zika virus can be spread from an infected person to their sexual partner through vaginal or anal sex. Some evidence suggests that Zika virus may also be transmissible through oral sex or by sharing sex toys.

Sexual transmission of Zika virus can occur through semen, vaginal fluid, or menstrual blood. The virus tends to remain in semen longer than in other body fluids. While Zika virus may be present in saliva, it’s generally believed that the virus can’t be transmitted through kissing.

Using a condom or temporarily practicing abstinence (not having sex) can help prevent the sexual spread of Zika. The CDC advises men and people assigned male at birth to use a condom or avoid sex for at least three months after a Zika diagnosis or possible exposure to Zika through travel. Women and people assigned female at birth should take these precautions for two months after exposure or diagnosis.

Pregnancy

A person who experiences Zika infection during pregnancy can transmit the virus to their fetus through the placenta. (The placenta is a temporary organ that connects the fetus to the uterus, or womb.) Around five percent of babies born to people with Zika infections have congenital differences, such as microcephaly or issues with brain development. A person who contracts Zika virus early in their pregnancy is most likely to pass the virus to their fetus.

Zika virus can also be found in breast milk, but there’s little evidence that the virus can be spread to a breastfeeding baby. The CDC generally recommends that women and people assigned female at birth with Zika virus disease continue breastfeeding, as the benefits of breastfeeding are believed to outweigh the risks of possible Zika transmission through breast milk.

Exposure to infected blood and body tissues

A few cases of Zika virus transmission through blood transfusions have been reported in Brazil and France. Such cases are rare, however, and have not been documented in the U.S. A person will likely need to delay donating blood, an organ, or other tissues following a Zika virus infection. Zika transmission is also possible through exposure to infected blood or tissues in a laboratory or healthcare setting.

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Traveling to or living in a country where Zika virus is present is the main risk factor for Zika virus disease. Parts of the world where Zika virus is most common include:

• The Caribbean
• Central and South America, excluding Chile
• Certain countries in Africa, including but not limited to Uganda, Ethiopia, Kenya, Angola, Senegal, Nigeria, and Mali
• Certain countries in Asia, including but not limited to India, Malaysia, Thailand, Vietnam, Indonesia, the Philippines, and Papua New Guinea

Pregnant people should avoid traveling to an area with active Zika virus transmission if possible. Before making travel plans, check the CDC website for the latest Zika travel health notices.

Engaging in sexual activities with someone infected by Zika virus also increases your risk of disease. Practicing abstinence or using a condom is the best way to prevent sexual transmission of Zika.

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Speak with an HCP if you live in or have recently traveled to a country where Zika virus transmission occurs and you’re experiencing possible symptoms of the condition. You should also speak with an HCP if you’re pregnant or are trying to become pregnant and live in or have traveled to an area with Zika, even if you don’t have symptoms.   

Keep in mind that Zika virus is uncommon. If you’re experiencing possible symptoms of Zika, you likely have a more common illness such as influenza (the flu) or a cold. Your HCP will be able to help determine the cause of your symptoms and provide appropriate treatment. If symptoms worsen, promptly seek medical care.

What questions should you ask your healthcare provider?

Asking your HCP questions can help you learn more about Zika virus and how to avoid it. Some common questions about Zika include:

• Am I at risk for Zika virus?
• If I have Zika virus disease, how long am I contagious? How can I prevent spreading the virus to others?
• What’s the best way to prevent getting Zika virus when I travel?
• How can I prevent mosquito bites?  
• How is Zika virus disease treated? What treatment options do you recommend?
• Is it safe to travel if I’m pregnant or am planning on becoming pregnant? What areas should I avoid?
• I’m pregnant and have a Zika virus infection. What should I do?
• Am I at risk for Zika virus complications?
• When should I call 911 or seek emergency care?

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Your HCP may consider testing for Zika virus disease if you:

• Recently traveled to or live in an area with Zika virus transmission and are experiencing possible symptoms
• Are pregnant, experiencing possible symptoms, and have recently traveled to or live in an area with Zika virus transmission
• Are pregnant, experiencing possible symptoms, and have had sexual contact with someone who may have been exposed to Zika virus  

Some HCPs recommend Zika virus testing for pregnant people who aren’t experiencing symptoms but have visited an area where Zika virus occurs.

You’ll likely be asked a serious of questions about your symptoms, where you’ve traveled recently, and if you’ve had sexual contact with someone who may have been exposed to Zika virus.

From there, your HCP may order a blood or urine test to screen for Zika virus or its antibodies. (Antibodies are proteins produced by the immune system in response to an infection.) Your HCP may give you other tests to rule out more common illnesses, such as the flu, and other illnesses caused by flaviviruses, such as dengue.

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There’s no cure or specific treatment for Zika virus disease. Like many other viral infections, Zika usually clears on its own. People who experience Zika symptoms typically feel better within a week or so.

If you develop Zika symptoms, your HCP may recommend self-care measures to ease symptoms and help your immune system fight off the infection. These include:

Stay hydrated. Drink plenty of water and eat foods with high water content, such as oranges, watermelon, bell peppers, pineapple, and soups. Avoid beverages that can contribute to dehydration, such as alcohol, caffeinated drinks, sodas, and sugary fruit juices.

Prioritize rest. Getting enough sleep and rest helps your body recover from infections like Zika. During sleep, the immune system produces illness-fighting antibodies that promote recovery. Most adults should aim to get between 7 and 9 hours of sleep daily, according to the CDC.

Take medication. Over-the-counter medication such as acetaminophen can help ease Zika symptoms like fever and muscle pain. Speak with your HCP before taking nonsteroidal anti-inflammatory drugs (NSAIDs) or aspirin, as these medications may increase the risk of bleeding in people with certain conditions.

Pregnant people who are diagnosed with Zika may receive additional prenatal care (specialized care designed for pregnant people). This might include tests to assess the health of the fetus.  

If you’ve received a Zika diagnosis and your symptoms worsen despite self-care measures, contact your HCP.

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There’s no vaccine to prevent Zika virus infection. But taking steps to avoid mosquito bites can help lower your risk of Zika virus disease as well as other bug-borne illnesses. Practicing safe sex can also help reduce your chances of Zika virus disease and sexually transmitted infections.

It’s also important to avoid traveling to areas with active Zika outbreaks. You can view current travel health notices on the CDC’s website.

Protect yourself from mosquito bites

It’s not always possible to avoid mosquito bites, but there are a few things you can do to make yourself and your space less attractive to mosquitoes.   

When spending time outdoors or traveling:

• Use an insect repellent according to package directions. Make sure the product is registered with the U.S. Environmental Protection Agency (EPA). 
• Wear loose and light-colored long-sleeved shirts and pants when possible. Pack plenty of these items when traveling to an area affected by Zika.
• Sleep under a mosquito net if staying outdoors or in a space exposed to mosquitoes.  
• Avoid wearing perfume, cologne, and heavily fragranced personal products, as these may attract mosquitoes.

While at home:

• Avoid leaving doors, windows, or garage doors propped open.  
• Install window and door screens to help keep mosquitoes out of your home.
• Regularly clean, cover, empty, pour out, or turn over things around your home or yard that can hold standing water. This might include above-ground pools, flowerpots, trash cans, storage containers, or outdoor toys.  
• Fill holes in trees to prevent water collection.
• Repair gaps or cracks in structures in and around your home, including plumbing pipes and your septic tank, if you have one.
• Consider hiring a pest control professional to treat your home or yard.

People who are naturally prone to getting bit by mosquitoes—such as those with type O blood—should be especially mindful about mosquito bite prevention.

Protecting yourself from mosquito bites is also important if you already have Zika virus disease. You can pass along the virus to mosquitoes that bite you. These mosquitoes can then spread Zika to people they bite.

Practice safe sex

Zika virus can spread from an infected person to their partner through vaginal or anal sex. Evidence also suggests the virus is transmissible through oral sex and the shared use of sex toys.

To prevent sexual transmission of Zika, the CDC advises people who have recently traveled to an affected area to use condoms or abstain from sexual activities for these periods of time, even if they don’t have symptoms:

• Men and people assigned male at birth should use condoms and dental dams or practice abstinence for at least three months after returning from travel. 
• Women and people assigned female at birth should use condoms and dental dams or practice abstinence for at least two months after returning from travel.

Proper use of male condoms, female condoms, and dental dams can help prevent the spread of Zika. Not having sex is the only way to completely eliminate the risk of sexual transmission of Zika.

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There’s no cure for Zika. That said, most people with Zika virus disease experience mild symptoms (if any at all) and make full recoveries. Zika rarely causes serious illness, complications, or death.

Pregnant people who develop Zika virus infection during their pregnancy have about a 5 percent chance of giving birth to a baby with congenital differences such as microcephaly. This risk of congenital differences is highest when infection occurs in the first trimester (first three months) of pregnancy.

Zika virus is uncommon, but some research estimates the virus could soon be on the rise. A 2020 study published in Global Change Biology projects that rising global temperatures could expand the habitat of Aedes mosquitoes and put an additional 1.3 billion people at risk of Zika virus by the year 2050.

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Researchers and HCPs are continuing to learn more about Zika virus, how it spreads, and what can be done to prevent Zika complications. Learn the latest information on Zika virus and current outbreaks from the Centers for Disease Control and Prevention or the World Health Organization.

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• 8 Ways to Reduce Your Risk of Getting Zika
• What Men Should Know About Zika  
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