Symptoms of the Zika Virus

While symptoms are often mild, complications can be severe

Feeding Mosquito.
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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.

Common Symptoms

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

Symptoms will usually appear two to seven days after being bitten by an infected mosquito and clear within three 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 a 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.

In around 50 percent of cases, GBS will develop in people who have had an extended bout of Zika symptoms, primarily fever, lasting from seven to 15 days.

The symptoms of GBS itself can persist for weeks and even months. Although most people will fully recover, some may have permanent nerve damage. Very few 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. If this happens during the early stages of gestation, the infection 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 the midpoint of your second trimester.

It is important to remember that getting a mosquito bite does 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 one percent to 13 percent.

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 infections whether you are at home and abroad.

Sources:

Centers for Disease Control and Prevention (CDC). "Birth Defects: Facts About Microcephaly." Atlanta, Georgia; updated December 7, 2017.

CDC. "Zika Virus." Updated February 22, 2018

Duffy, M.; Chen, T.; Hancock, W. et al. "Zika virus outbreak on Yap Island, federated states of Micronesia." N. Engl J Med. 2009; 360:2536-43, DOI: 10.1056/NEJMoa0805715.

European Centre for Disease Prevention and Control. "Zika virus epidemic in the Americas: potential association with microcephaly and Guillain-Barré syndrome (first update)." Stockholm, Sweden: ECDC; 2016.

McCarthy, M. "Microcephaly risk with Zika infection is 1-13% in the first trimester, study shows." BMJ. 2016;353:i3048. DOI: 10.1136/bmj.i3048.