The Zika (ZEE-kuh) virus is most often spread to people through mosquito bites, primarily in tropical and subtropical areas of the world. Most people infected with the Zika virus have no signs and symptoms. Some people have mild fever, rash and muscle pain. In rare cases, the Zika virus may cause brain or nervous system complications, such as Guillain-Barre syndrome, even in people who never show symptoms of infection. Infection with the Zika virus is also called Zika, Zika fever or Zika virus disease.

Women who are infected with the Zika virus during pregnancy have an increased risk of miscarriage. Zika virus infection during pregnancy also increases the risk of serious birth defects in infants, including a potentially fatal brain condition called microcephaly.

Researchers are working on a vaccine for the Zika virus. For now, the best way to prevent infection is to avoid mosquito bites and reduce mosquito habitats.

As many as 4 out of 5 people infected with the Zika virus have no signs or symptoms. When symptoms do occur, they usually begin two to 14 days after a person is bitten by an infected mosquito. Symptoms usually last about a week, and most people recover fully.

Signs and symptoms of the Zika virus most commonly include:

• Mild fever
• Rash
• Joint pain, particularly in the hands or feet
• Red eyes (conjunctivitis)

Other signs and symptoms may include:

• Muscle pain
• Headache
• Eye pain
• Fatigue or a general feeling of discomfort
• Abdominal pain

When to see a doctor

See your doctor if you think you or a family member may have the Zika virus, especially if you have recently traveled to an area where there's an ongoing outbreak. The U.S. Centers for Disease Control and Prevention (CDC) has blood tests to look for the Zika virus and other viruses spread by mosquitoes.

If you're pregnant and have recently traveled to an area where the Zika virus is common, ask your doctor whether you should be tested, even if you don't have symptoms.

The Zika virus is most often spread to a person through the bite of an infected mosquito. The mosquitoes that are known to carry the virus include two aedes species mosquitoes, which can be found throughout the world.

When a mosquito bites a person who is already infected with the Zika virus, the virus infects the mosquito. Then, when the infected mosquito bites another person, the virus enters that person's bloodstream and causes an infection.

During pregnancy, the Zika virus can also spread from a mother to the fetus.

The virus can also spread from one person to another through sexual contact. In some cases, people contract the virus through blood transfusion or organ donation.

Factors that put you at greater risk of catching the Zika virus include:

• Living or traveling in countries where there have been outbreaks. Being in tropical and subtropical areas increases your risk of exposure to the Zika virus. Especially high-risk areas include several of the Pacific Islands, a number of countries in Central, South and North America, and islands near West Africa. Because the mosquitoes that carry the Zika virus are found worldwide, it's likely that outbreaks will continue to spread to new regions.

  Most cases of Zika virus infection in the U.S. have been reported in travelers returning to the U.S. from other areas. But the mosquitoes that carry the Zika virus do live in some parts of the United States and its territories. Local transmission has been reported in Florida, Texas, the U.S. Virgin Islands and Puerto Rico.

• Having unprotected sex. The Zika virus can spread from one person to another through sex. Having unprotected sex can increase the risk of Zika virus infection for up to three months after travel. For this reason, pregnant women whose sex partners recently lived in or traveled to an area where Zika virus is common should use a condom during sexual activity or abstain from sexual activity until the baby is born. All other couples can also reduce the risk of sexual transmission by using a condom or abstaining from sexual activity for up to three months after travel.

Women who are infected with the Zika virus during pregnancy have an increased risk of miscarriage, preterm birth and stillbirth. Zika virus infection during pregnancy also increases the risk of serious birth defects in infants (congenital Zika syndrome), including:

• A much smaller than normal brain and head size (mirocephaly), with a partly collapsed skull
• Brain damage and reduced brain tissue
• Eye damage
• Joint problems, including limited motion
• Reduced body movement due to too much muscle tone after birth

In adults, infection with the Zika virus may cause brain or nervous system complications, such as Guillain-Barre syndrome, even in people who never show symptoms of infection.

There is no vaccine to protect against the Zika virus. But you can take steps to reduce your risk of exposure to the virus.

If you or your partner is pregnant or trying to get pregnant, these tips may help lower your risk of Zika virus infection:

• Plan travel carefully. The CDC recommends that all pregnant women avoid traveling to areas where there is an outbreak of the Zika virus.

  If you're trying to become pregnant, talk to your doctor about whether you or your partner's upcoming travel plans increase the risk of Zika virus infection. Your doctor may suggest you and your partner wait to try to conceive for two to three months after travel.

• Practice safe sex. If you have a partner who lives in or has traveled to an area where there is an outbreak of the Zika virus, the CDC recommends abstaining from sex during pregnancy or using a condom during all sexual activity.

If you are living in or traveling to areas where the Zika virus is known to be, take steps to reduce your risk of mosquito bites:

• Stay in air-conditioned or well-screened housing. The mosquitoes that carry the Zika virus are most active from dawn to dusk, but they can also bite at night. Consider sleeping under a mosquito bed net, especially if you are outside.
• Wear protective clothing. When you go into mosquito-infested areas, wear a long-sleeved shirt, long pants, socks and shoes.
• Use insect repellent. You can apply permethrin to your clothing, shoes, camping gear and bed netting. You can also buy clothing made with permethrin already in it. For your skin, use a repellent that contains DEET, picaridin, or one of the other active ingredients registered with the Environmental Protection Agency and known to be effective against mosquitoes. When used as directed, these repellents are proven safe and effective, even for pregnant and breastfeeding women.
• Reduce mosquito habitat. The mosquitoes that carry the Zika virus usually live in and around houses and breed in standing water that has collected in containers such as animal dishes, flower pots and used automobile tires. At least once a week, empty any sources of standing water to help lower mosquito populations.

The Zika virus and blood donation

In some cases, the Zika virus has spread from one person to another through blood products (blood transfusion). To reduce the risk of spread through blood transfusion, blood donation centers in the United States and its territories are required to screen all blood donations for the Zika virus. If you had Zika or if you live in the U.S. and recently traveled to an area where the Zika virus is widespread, your local blood donation center may recommend that you wait four weeks to donate blood.

Your doctor will likely ask about your medical and travel history. Be sure to describe any international trips in detail, including the countries you and your sexual partner have visited, the dates of travel, and whether you may have had contact with mosquitoes.

If your doctor suspects that you may have a Zika virus infection, he or she may recommend a blood or urine test to confirm the diagnosis. The blood or urine samples can also be used to test for other, similar mosquito-borne diseases.

If you are pregnant and don't have symptoms of Zika virus infection but you or your partner recently traveled to an area with active Zika virus transmission, ask your doctor if you need to be tested.

If you are pregnant and at risk of Zika virus infection, your doctor may also recommend one of the following procedures:

• An ultrasound to look for fetal brain problems
• Amniocentesis, which involves inserting a hollow needle into the uterus to remove a sample of amniotic fluid (amniocentesis) to be tested for the Zika virus

There is no specific treatment for infection with the Zika virus. To help relieve symptoms, get plenty of rest and drink plenty of fluids to prevent dehydration. The over-the-counter (OTC) medication acetaminophen (Tylenol, others) may help relieve joint pain and fever.

The symptoms of Zika virus infection are similar to other mosquito-borne illnesses, such as dengue fever. If you're feeling ill after recent travel to an area where mosquito-borne illness is common, see your doctor. Don't take ibuprofen (Advil, Motrin IB, others), naproxen sodium (Aleve) or aspirin until your doctor has ruled out dengue fever. These medications can increase the risk of serious complications from dengue fever.

You'll likely start by seeing your primary care doctor. But you might be referred to a doctor who specializes in infectious diseases or travel medicine.

Because appointments can be brief, and because there's often a lot to discuss, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready, and what to expect from your doctor.

What you can do

Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.

• Write down key personal information. List your international travel history, with dates and countries visited, and medications taken while traveling. Bring a record of your vaccinations, including pre-travel vaccinations.
• Make a list of all your medications. Include any vitamins or supplements you take regularly.
• Write down questions to ask your doctor. Preparing a list of questions can help you make the most of your time with your doctor. List your questions from most important to least important in case time runs out.

For Zika virus infection, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• What kinds of tests do I need?
• What treatments are available?
• How long will it be before I'm feeling better?
• Are there any long-term effects of this illness?
• Do you have any brochures or other printed material that I can take home with me? What websites do you recommend?

What to expect from your doctor

Be prepared to answer questions from your doctor, such as:

• When did your symptoms begin?
• Are you pregnant or trying to become pregnant? Do you use condoms?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• Does anything seem to make your symptoms better or worse?
• Where have you traveled in the past month?
• Were you bitten by mosquitoes while traveling?
• Have you been in contact recently with anyone who was ill?