Symptoms of the Zika Virus

While symptoms are often mild, complications can be severe

A Zika virus infection, also known as Zika fever or Zika virus disease, usually causes mild, transient symptoms or no symptoms at all. When signs of infection do appear, they are often non-specific and easily mistaken for the cold or flu. By contrast, congenital infections (passed from mother to child during pregnancy) can be far more serious and lead to a potentially devastating birth defect known as ​microcephaly.

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Common Symptoms

According to research published in the New England Journal of Medicine, as many as 80% of Zika infections will be entirely asymptomatic (without symptoms). When symptoms do appear, they most commonly include:

Symptoms will usually appear three to 14 days after being bitten by an infected mosquito and clear within two to seven days. While the Zika virus can be distinguished from a cold or flu by the absence of respiratory symptoms (such as coughing or sneezing), the infection can only be confirmed with the combination of blood and urine tests.

Complications of Infection

In rare cases, a Zika infection may lead to a serious condition known as Guillain-Barré syndrome (GBS) in which a person's immune system attacks its own nerve cells. While the condition is considered rare, it can lead to arm and leg weakness and, in severe cases, the impairment of the muscles that control breathing.

The symptoms of GBS can persist for weeks and even months. Although most people will fully recover, some may have permanent nerve damage. A small percentage of people die from GBS.

Microcephaly in Babies

While the Zika virus rarely causes serious illness in adults or children, the consequences of an infection can be far worse if transmitted during pregnancy. Particularly during the early stages of gestation, infection with Zika may cause a birth defect known as microcephaly, in which the baby is born with an abnormally small head and brain.

Microcephaly can cause a cascade of physical, neurological, and developmental symptoms, including:

  • Epilepsy
  • Developmental delays, including problems with speech and other developmental milestones such as sitting, standing, or walking
  • Intellectual disability
  • Cerebral palsy
  • Feeding problems, including difficulty swallowing (dysphagia)
  • Hearing loss
  • Vision problems, including glaucoma
  • Impaired growth

Microcephaly may be mild or severe. The severity of symptoms is typically related to the reduced size of the baby's head. In some cases, the child will develop normally with no signs of impairment. In others, the defect can be severe and lead to lifelong disability and a shortened lifespan.

Babies born with microcephaly would be closely monitored even if there are no outward signs of disability. Some of the complications of the defect, such as cerebral palsy or epilepsy, may only develop in later life.

There is no standard treatment for microcephaly and nothing one can do to return the baby's head to its normal size. Occupational, speech, and physical therapy may be used to help overcome severe disabilities, while medications can help control seizures and other medical problems.

When to See a Doctor

Any person who has traveled or lives in a region where the Zika virus is endemic should be tested if symptoms of infection appear. This is especially true if you are pregnant.

The Centers for Disease Control and Prevention (CDC) urges any asymptomatic pregnant woman to be tested two to 12 weeks upon her return from an endemic region. Those with symptoms should be tested immediately. If you happen to live in an endemic region, you would need to be tested during your first prenatal visit and at two other points during the course of your pregnancy.

It is important to remember that getting a mosquito bite does not mean that your baby will be born with a birth defect. Even in northeastern Brazil, an area hit hard by the Zika outbreak of 2016, the risk of microcephaly among affected women ran anywhere from 1% to 13%.

While the Zika virus should definitely warrant concern, it shouldn't cause panic. With the right precautions, you and your family can greatly reduce your odds of infection whether you are at home or abroad.

Frequently Asked Questions

What are the common symptoms of Zika virus?

Most cases of Zika virus cause no symptoms but, when signs and symptoms do develop, they tend to be mild and include:

  • Fever
  • Rash
  • Headache
  • Conjunctivitis ("pink eye")
  • Joint pain
  • Muscle pain

How soon after a bite do Zika symptoms start?

Zika virus is transmitted via mosquitos of the Aedes genus. Once bitten, the incubation period of the virus is three to 14 days.

How long do Zika symptoms last?

If symptoms of Zika virus develop, they tend to be mild and resolve without treatment within several days to one week.

What does a Zika rash look like?

A Zika virus rash is maculopapular, meaning that it consists of flat, raised blotches (macules) and tiny reddish bumps (papules). The rash may be itchy and will typically be widespread (disseminated), starting on the trunk and spreading to the legs, arms, feet, hands, and face.

What are the possible complications of Zika virus?

A Zika infection during pregnancy can lead to birth defects, including microencephaly. In the United States, between 5% and 10% of babies born to mothers with confirmed Zika infections developed birth defects during the 2016-2017 outbreak. Among adults, Zika has been known to trigger the autoimmune nerve disorder Guillain-Barré syndrome.

Can Zika virus kill you?

There have been very few reported deaths linked to primary Zika virus infection. Among children born with Zika-associated microencephaly, the death rate is around 10%.

Zika Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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