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What You Need to Know About the Zika Virus

Betsy Herold, MD
Vice Chair for Research, Department of Pediatrics
Chief, Division of Pediatric Infectious Diseases, Department of Pediatrics
Director, Translational Prevention Research Center

Zika is the latest emerging infectious disease to take advantage of the increase in urbanization and global traffic that the world has seen over the last 50 years. The virus was discovered in Uganda in 1947 when scientists were studying a related virus in rhesus monkeys, but was ignored for70 years for several reasons. First, it was viewed as the “milder dengue” virus. Secondly, only sporadic reports were published in travelers returning from Uganda.

However, in 2007, the first sign of how quickly Zika can spread through a population not previously exposed to the virus was observed on the Yap Islands in Micronesia in the Pacific Ocean. A 2007 Zika virus outbreak thereaffected an estimated 70% of the island’s population three years of age and older.

Scientists speculate that a large international event such as the Va’a World Sprint Championship canoe race, in which several Pacific countries participated, led to the introduction of Zika into the Americas. The virus is then carried by Aedesaegyptimosquitos, which are prevalent in urban areas. Zika has already affected over 30 countries and territories and will likely spread to countries in which these mosquitoscirculate. This includes all the countries in the Western Hemisphere,except for Chile and Canada. Although US cases are currently documented only in travelers, it is likely, in the near future, that the same southern states in which local transmission of dengue or chikungunya virusis observed will report Zika.

Zika is a member of the flavivirus family and is transmitted primarily by mosquitos, but intrauterine, intrapartum, blood and sexual transmission have also been documented. Most people who contract the virus are asymptomatic. Those that do show signs of infection exhibit symptoms very similar to other viruses spread by the Aedesaegypti, mosquito, such asdengue and chikungunya. Symptoms include fever, rash, red eyes (known as conjunctivitis), joint or muscle pains and headache.

Because the virus has not been previously recognized as major global health problem, diagnostic testing is limited. Zika virus testing is only available through the Department of Health or Centers for Disease Control (CDC). Testing includes detection of viral RNA by reverse- transcriptase polymerase chain reaction (RT-PCR) and serological testing for IgM antibodies by ELISA or IgG neutralizing Abs by a plaque reduction neutralization test. However, antibodies to Dengue, yellow fever and other flaviviruses may cross react, so results must be interpreted cautiously.

Testing is currently being offered to:

  • Patients who traveled to a region with Zika and who were pregnant at the time of travel
  • Patients who were symptomatic within four weeks of travel
  • Newborns born to mothers with suspected or confirmed Zika

There is mounting evidence that Zika virus is at least a contributing factor in the increased rates of microcephaly (small head) observed in newborn infants in Brazil. Congenital disease may also be associated with other neurological abnormalities. In light of these concerns, the CDC advises that pregnant women or women planning to become pregnant in the very near future should not travel to Zika areas at this time. The CDC also counsels that men with pregnant partners who travel to endemic regions consistently use condoms and/or abstain from sex for the duration of the pregnancy.

There are no current medicines that target the virus. Although vaccine trials are underway, widespread availability of a Zika virus vaccine is unlikely to be available for several years.

The Pediatric Infectious Disease Division is happy to provide advice for families considering travel to areas where Zika is prevalent and to providers who are concerned about patients who may have been exposed or infected. Please contact the Travel Clinic (1-718-741-2450).

Additional information can be found at: (including information on countries currently reporting active transmission).


Duffy MR, Chen T, Hancock WT et a. Zika Virus Outbreak on the Yap Island, Federal States of Micronesia NEJM 2009;360:2536-2543.

Fauci AS and Morens DM Zika Virus in the Americas – Yet AnotherArbovirus Threat. NEJM 2016; 374:601-604.

Mlakar J, Korva M, Tul N et al.Zika virus associated with microcephaly. NEJM DOI: 10.1056/NEJMoa1600651

Schuler-Faccini L, Ribeiro EM, Feitosa IM, et al. Possible association between Zika virus infection and microcephaly — Brazil, 2015. MMWR 2016;65:59-62.