Zika: What You Need to Know

Although the Zika virus was discovered in 1947, a recent epidemic centered in Brazil has raised the profile of this microbe. As cases in the South American country have surged due to the spread of infection by the Aedes mosquito, the medical community has realized a link between the mosquito-borne cause of disease and the sharp increase in babies born with microcephaly, a condition in which the head is abnormally small, often because the brain fails to fully develop. Zika also can cause other birth defects or even miscarriage.

This is why the virus, which normally produces few or no symptoms, has become such a concern among women who are or might become pregnant in the near future. A related discovery, that Zika can be transmitted in the semen of infected men, has raised new concerns for the female partners of men who travel to Aedes-infested regions.

1. Where Is Zika?

Right now, Zika is being actively transmitted in numerous countries in Central and South America as well as the Caribbean. There are a small number of cases in the continental United States, but none of those cases were contracted in the U.S. Without exception, people in the United States with Zika acquired the infection while traveling or through contact with someone who traveled outside the U.S.

It is strongly recommended that women who are pregnant or who are planning to become pregnant in the near future avoid going to tropical destinations where the virus is currently prevalent, including areas such as the Caribbean, Mexico, Central America and South America.

2. How Many People Have the Zika Virus?

Today’s numbers are likely not tomorrow’s numbers. The situation changes very rapidly, and the full scale of the epidemic may yet to be discovered because many of the pregnant women currently infected have not yet given birth.

It’s likely that many hundreds of thousands of people are or soon will be infected. Experts are in agreement that infection numbers will continue to rise—possibly into the millions—unless infection-control protocols are put in place and followed.

3. How Do You Know if you Have Zika?

The most common symptoms of Zika include:

  • a rash that begins on the head and spreads
  • conjunctivitis (eye inflammation)
  • fever (usually mild)
  • headache
  • joint and muscle pain
  • nausea
  • swollen lymph glands

The symptoms usually appear a few days after being bitten, are not terribly severe, and are gone within a few days to a week. But as 75% to 80% of people with Zika never exhibit any symptoms at all, you might not know you have the virus unless your doctor orders your blood to be tested.

"These tests are not currently available commercially," says Aileen Marty, MD, professor of infectious diseases in the Department of Medicine at the Florida International University Herbert Wertheim College of Medicine in Miami. "They have to be done at the CDC (Centers for Disease Control and Prevention) or in some state health departments [that] have the capability to do the tests."

However, this will likely change in the near future, says Aaron Glatt, MD, an epidemiologist and chair of medicine at South Nassau Communities Hospital in Oceanside, New York, as tests are quickly being developed so local labs can do on-site testing.

4. Do all Pregnant Women Infected With Zika Miscarry or Deliver Babies With Deformities?

In one recent study, 27 percent of women who contracted Zika while pregnant had miscarriages or delivered babies with deformities. Other studies suggest a much lower rate of serious outcomes. However, experts are quick to stress that they don’t know at any given time how many women with Zika will have babies with problems. Even if the number is much less than 27 percent, given the large number of people at risk of contracting the virus, that translates into potentially thousands of problem pregnancies.

5. Are You at Less Risk if You’re far Along in Your Pregnancy?

Apparently, you’re at risk whether you’re planning to conceive soon or are about to deliver. While it may seem as though a fetus in the first trimester would be at greater risk due to the rapid development of its organs at that time, women later in pregnancy are not automatically in the clear. "It certainly is probably less [problematic to be infected in the third trimester], but we don’t know," Glatt says. It’s possible that a baby could still be born with problems or even develop them after birth if the mother is infected close to delivery.

The latest guidelines for the timing of conception are for infected women to wait at least eight weeks to conceive after the onset of symptoms and for infected men to wait at least six months. In the case of possible infection, both women and men should wait eight weeks after exposure to conceive.

6. Are There any Other Risks Besides Those to Fetuses?

In nine countries so far, a small but growing number of people infected with Zika have developed Guillain-Barre syndrome, a form of paralysis that is usually temporary but progresses to death in about five percent of cases.

7. How Is Zika Treated?

Currently, there is no preventive vaccine or antiviral drug to treat Zika. The best protection is prevention—don’t get bitten in the first place. People living in or traveling to places where Zika is common are advised to wear long sleeves and pants, liberally apply insect repellent, keep windows closed, and sleep under mosquito netting. It’s also important to avoid getting bitten again once you’re infected, because mosquitoes can carry Zika from one person to another.

Reviewed by Aaron Glatt, MD, FACP, FIDSA, FSHEA, epidemiologist and chair of medicine at South Nassau Communities Hospital in Oceanside, New York, on March 29, 2016.


Glatt, Aaron, MD, FACP, FIDSA, FSHEA. Phone interview. March 16, 2016.

Marty, Aileen, MD, FCAP. Email exchange with author. March 16, 2016.

"Zika Virus." World Health Organization. Updated March 18, 2016.

"Update: Interim Guidance for Health Care Providers Caring for Women of Reproductive Age with Possible Zika Virus Exposure—United States, 2016." Centers for Disease Control and Prevention. Updated April 1, 2016.  

"Zika and Guillain-Barre Syndrome." Centers for Disease Control and Prevention. Updated March 10, 2016.

"Facts About Microcephaly." Centers for Disease Control and Prevention. Updated on April 7, 2016.