An Overview of the Zika Virus

2016 outbreak spotlights the danger of infection during pregnancy

Aedes aegypti mosquitos are seen in a lab at the Fiocruz institute on January 26, 2016 in Recife, Pernambuco state, Brazil. The mosquito transmits the Zika virus and is being studied at the institute.
Mario Tama/Getty Images News/Getty Images

The Zika virus is a transmittable disease that is spread through mosquito bites. While most infections will cause few, if any, symptoms, the disease can turn catastrophic if it is passed from mother to child during pregnancy. Doing so may lead to an irreversible birth defect known as microcephaly in which a baby is born with an abnormally small head and brain.

Largely unheard of before 2015, the Zika virus caused worldwide panic when a massive outbreak cut a path of infection from South and Central America right up to the southern part of the United States in 2016.

Zika is a relatively new virus, first isolated from a monkey in Uganda back in 1947. While scientists had initially believed that the virus was constrained to simian populations, the first evidence of a leap from animal to human was reported in 1952. Genetic research has since revealed that was the virus had been established in humans well before then, passed from person to person through the Aedes aegypti mosquito, a strain prevalent in tropical and subtropical regions throughout the world.

In 2015, the first western hemisphere infections were reported in northeast Brazil. Within the span of two years, the rate microcephaly in the region had spiked to alarming rates. In Columbia alone, no less than 476 cases were confirmed in 33 surveillance sites (translating to around one case per 1,000 births).

Similar results were seen in Brazil which reported over 3,000 microcephalic births directly related to Zika.

It is this heartbreaking complication that led governments to implement better control measures and to educate the public on the symptoms, treatment, and prevention of this still largely misunderstood disease.

Causes and Risks

The Zika virus is a member of the virus family Flaviviridae and is closely related to other mosquito-borne diseases such as dengue fever and yellow fever. It is passed from person to person in one of three ways:

  • By a mosquito bite from the Aedes aegypti mosquito
  • During pregnancy when it is passed from an infected mother to her unborn baby
  • During unprotected oral, vaginal, or anal sex

It only takes one bite to become infected.

In terms of sexual transmission, the virus is able to persist in semen where it is less able to do so in saliva or vaginal secretions. As such, Zika is more commonly passed from man to woman rather than the other way around.

Symptoms

In adults and children, Zika will usually cause a mild, self-limiting illness or have no symptoms at all. When symptoms do develop, they may appear flu-like with fever, headache, muscle and joint pain, and possibly rash. Symptoms tend to clear within three to seven days along with any evidence of the virus.

The story is entirely different if transmission occurs during pregnancy. If this happens, the developing fetus may be affected, leading to miscarriage, stillbirth, or, in rare instances, congenital birth defects. The most serious of these is microcephaly.

Microcephaly is a devastating disorder characterized by lifelong disabilities, including:

  • Seizures
  • Developmental delays
  • Intellectual disability
  • Problems with movement and balance
  • Feeding problems
  • Hearing loss
  • Vision problems

The severity of symptoms is typically related to the reduced size of the child's head and brain. Many babies born with microcephaly will have no symptoms at birth but develop epilepsy, cerebral palsy, and other problems later in life. In some cases, a child may develop perfectly normally.

The risk of microcephaly is greatest during the first trimester of pregnancy. By contrast, a Zika infection that occurs during the second or third trimester poses little to no risk.

Diagnosis

A Zika infection can be diagnosed with tests that can either directly detect the organism or indirectly confirm evidence of infection The testing procedure can vary but usually involves two separate tests used in tandem:

  • Nucleic acid testing (NAT) is used to detect genetic evidence of the Zika virus. The NAT test would be performed concurrently on both a blood and urine sample.
  • Immunoglobulin M (IgM) testing is used to detect proteins, known as antibodies, that are produced by the body in response to the Zika infection. The test is blood-based and usually able to detect antibodies within four days of the appearance of symptoms.

Testing Recommendations

While the diagnosis of a Zika infection is relatively simple, it is not for everyone. Testing is currently recommended for the following at-risk groups only:

  • Any symptomatic person believed to be exposed to the virus either through unprotected sex or recent travel to a region where Zika is endemic
  • Any pregnant woman believed to be exposed to the virus either due to recent travel to an endemic region or unprotected sex with a person who recently returned from an endemic region

The test is not recommended for non-symptomatic persons who are not pregnant or as a form of preconception screening.

Treatment

There is no treatment for a Zika infection. Acute symptoms may be treated with Tylenol (acetaminophen).

Prevention

There is no vaccine to prevent or cure the Zika virus. Efforts would, therefore, be centered on preventing mosquito-borne infections and reducing the risk of sexual transmission.

If living in or traveling to areas where the Zika virus is endemic, preventive efforts would include:

  • Using an insect repellent
  • Wearing protective clothing
  • Sleeping under a mosquito net
  • Getting rid of standing water where mosquitoes can breed
  • Closing windows and vents and using air conditioning
  • Checking travel health advisories when planning a trip

To reduce your risk of sexual exposure, condoms should be used if your partner has just returned from an endemic region. The duration may be a short as eight weeks if there are no symptoms or as long as six months or more if there are. Insect repellent should also be used for at least three weeks to prevent human-mosquito-human transmission.

A Word From Verywell

As scary as the Zika virus may seem, it is important to remember that getting a mosquito bite does not mean you will get the virus or that your unborn baby will be harmed. In fact, the majority of affected pregnancies do not result in birth defects or harm of any sort.

By simply being aware the factors that place you at risk, you and your partner can take the necessary steps to avoid infection and ensure that your baby is born safely.

Sources:

Centers for Disease Control and Prevention. "Diagnostic Tests for Zika Virus." Atlanta, Georgia; updated February 28, 2018.

Gubler, D.; Vasilakis, N.; and Musso, D. "History and Emergence of Zika Virus." J Infect Dis. 2017; 216(Suppl 10): S86-S867. DOI: 10.1093/infdis/jix451.

Oster, A.; Brooks, J.; Stryker, J. et al. "Interim Guidelines for Prevention of Sexual Transmission of Zika Virus - United States, 2016." MMWR. 2016; 65(5):120-1. DOI: 10.15585/mmwr.mm6505e1.