CDC issues travel warning amidst Zika virus outbreak: Experts weigh in on birth defects, vaccines and mosquitoes

The Centers for Disease Control and Prevention (CDC) has issued a travel alert for those traveling to regions in Latin America where the Zika virus outbreak is ongoing. In light of increasing evidence that Zika infection is linked to birth defects, the CDC also suggested pregnant women should postpone travel and women trying to get pregnant should consult their healthcare provider before travel. GENeS reached out to experts to find out what is need to establish for certain whether Zika virus is causing the wave of birth defects in Brazil; what is known about development of a vaccine for this virus; and which mosquito species could potentially spread the virus in the United States.

Previous comments sent by GENeS on this story can be found here:

Read the GENeS fact sheet on Zika virus here:


Dr. Nikos Vasilakis, Associate Professor, Department of Pathology, Member, Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch (webpage):

Expertise: evolution and pathogenesis of arthropod-borne viruses, virus-mosquito & virus-host interactions and vaccine development

“There is strong evidence providing a link between Zika virus infection during the first trimester of pregnancy and microcephaly. Furthermore, the presence of Zika viral RNA in the amniotic fluid in pregnant women of fetuses diagnosed with microcephaly as well as in the brains of newborns that were delivered stillborn or died at birth suggests infection during pregnancy. However, we ought to be aware that in the vast majority of newborns with microcephaly, direct detection of Zika virus is not possible because we see the results of events that occurred several months ago.

“To establish Zika virus infection during pregnancy it will be crucial to develop a Zika-specific ELISA (Enzyme Linked Immunosorbent Assay, a diagnostic test) that can detect antibodies generated in response to Zika infection. Immunoglobulin M antibodies are produced by the body as the first line of defense during any challenge to the immune system. Because they are large, they do not cross the placenta and can be used to detect infection with Zika during pregnancy.

“An additional challenge is to determine the time-window during pregnancy where infection with Zika increases the probability of microcephaly, for which the development of an animal model would be of outmost importance.

“Currently there is no FDA-licensed vaccine against Zika nor any antivirals. There is intense pressure for the development of such countermeasures. Given the existence of highly successful and efficacious vaccines against yellow fever and Japanese encephalitis viruses, which are closely related to Zika virus, development of a live attenuated or chimeric vaccine would be straightforward. However, we need to be aware that for any vaccine the development time, from the bench top to market, could take 10 years or more and several hundred million dollars in development costs.”


Dr. Daniel R. Lucey, Senior Scholar, O’Neill Institute for National and Global health Law, Georgetown University Law Center, Adjunct Professor of Medicine, Georgetown University (webpage):

Expertise: Global emerging infectious diseases

Zika virus and microcephaly

“To prove causation between Zika virus and microcephaly would require a combination of evidence from virology and epidemiology studies, along with work in animal models. The time course for the virologic and epidemiologic studies is at least a few months and for developing an animal model (or models) could be many months.

“A) Virology

  1. We would need to find evidence of a Zika virus infection in children born with microcephaly.
  2. We would need to find evidence of Zika virus infection in the mothers of these children.
  3. Perform tests for other known causes of microcephaly either infectious (rubella virus, cytomegalovirus, toxoplasmosis) or non-infectious causes to rule them out.
  4. Perform tests for possible co-factors suggested e.g., both dengue virus infection and Zika virus infection during pregnancy.

“B) Epidemiology

  1. Performing a Case-Control study to determine if pregnant women who are infected with Zika virus during pregnancy are more likely to have a child born with microcephaly.
  2. Determine during what trimester of pregnancy did the Zika virus occur. An infection in the first trimester might be more likely to cause microcephaly than later in pregnancy.

“C) Animal Models

  1. Some experts would also require an animal model of experimental Zika virus infection to determine if Zika virus alone, or in combination with other factors, causes microcephaly.

Vaccine(s) against Zika virus

“There are no licensed vaccines against the Zika virus anywhere in the world. A US-initiated Zika vaccine has only started very recently. Assuming that the scientific and pharmaceutical industry challenges can be met as quickly as possible, based on past new vaccine development timelines, we are several years away from having an FDA-licensed Zika vaccine that has been demonstrated to be both safe and effective.

“Perhaps the recent experience with experimental Ebola vaccines (none yet licensed) being studied during the ongoing epidemic in West Africa could expedite the vaccine development and testing process for candidate experimental Zika vaccines. One major difference, however, is that to my knowledge there are no experimental Zika vaccines even ready for phase I (safety) human vaccine trials , let alone the phase II (safety and immunogenicity), or phase III (safety, immunogenicity, and efficacy) studies. In contrast, there were some experimental candidate Ebola vaccines ready for phase I human vaccine trials in 2014 after the Ebola epidemic was finally recognized in West Africa.”


Dr. Peter Armbruster, Associate Professor of Biology, Georgetown University (webpage):

Expertise: Evolution and molecular basis of adaptation in Aedes albopticus

Aedes aegpyti and Aedes albopictus are both in the same sub-genus (Stegomyia) and are capable of transmitting several of the same viruses (e.g., all four serotypes of Dengue and Chikungunya). As Anthony Fauci suggested recently in the New England Journal of Medicine, the possibility that Ae. albopictus could transmit Zika is certainly of concern.

“In the case of Chikungunya, the virus incurred a mutation that made Ae. albopictus more competent to transmit the virus (relative to Ae. aegypti). So it is possible that the same thing could happen with Zika. Also, Ae. aegypti is already established in some subtropical regions of the U.S.—mostly Florida—so even if Ae. albopictus does not become involved in transmission of Zika, there is still a public health concern with Zika based on the presence of Ae. aegypti in the U.S.”


Declared interests (see GENeS register of interests policy):

No interests declared

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