Zika’s Unknown, Devastating Road Ahead

Seven Zika vaccines in clinical trials with forty in preclinical development
mom and young daughter walking on beach at sunset
(Zika News)

The Zika pandemic is still unfolding in unprecedented ways.

As of December 20, 2017, there have been 385 symptomatic Zika virus disease cases reported in the USA, with 97 percent of these cases identified in international travelers.

The vast majority of the Zika cases in 2017 were reported in California (92), New York (61), Florida (46), and Texas (46), reports the Centers for Disease Control and Prevention (CDC).

Because of the Zika virus insidious ability to harm unborn children, the pandemic has captured the attention of infectious disease researchers worldwide.

Since 2016, when the Zika virus was declared a public health emergency, it has reached more than 80 countries, infected millions of people, and left hundreds of babies with birth defects.

As of late 2017, a total of 2,364 confirmed Zika-related pregnancies in the USA have been reported to the Zika Pregnancy and Infant Registries.

Although scientists have made progress in their understanding of the virus, and are working toward treatments and preventive vaccines, it would be premature to think that the Zika pandemic is now under control and will not reemerge, reported Anthony S. Fauci, M.D., and David Morens, M.D.

These leaders from the National Institute of Allergy and Infectious Diseases published a special supplement examining the current scientific knowledge about the Zika virus and identified the key research questions that remain.

Unquestionably, the most disturbing aspect of this pandemic is the Zika-associated microcephaly birth defects, as well as fetal losses.

To make matters worse, it is suspected that many infected babies born in apparent health will manifest delayed effects of intrauterine Zika virus infection as they mature.

A critically important, but not achieved, research goal, is the development of a preventive Zika vaccine.

At least 7 different Zika vaccines are currently in clinical trials, with 40 more in ongoing preclinical development.

Zika vaccine trials face significant challenges, including the fact that the Zika pandemic is waning in many areas and that flavivirus outbreaks normally appear sporadically and unexpectedly.

Finally, it is important that we not assume that the Zika pandemic is a one-time crisis that can be met, controlled, and then relegated to historical review.

Over the past 4 decades, we have seen the dawn of a new infectious disease era in which mostly quiescent arboviruses have begun to aggressively emerge around the globe, including the dengue virus, West Nile virus, and chikungunya virus.

The Zika virus was spread around the world by a nonsylvatic-vector mosquito, the globally ubiquitous Aedes aegypti. The A. aegypti mosquito prefers blood meals from human beings, as opposed to other animal hosts.

Some evidence also suggests that at least 3 other Aedes mosquito species have also vectored Zika outbreaks. This is of great concern because of the possibility that Zika virus may be able to adapt to become more efficiently transmitted by new vectors.

In addition to vector transmission, Zika virus also is transmitted from mothers to fetuses, via sexual transmission and possibly through blood transfusion and organ transplantation.

These realities greatly complicate public health control efforts.

All the tropical world and much of the temperate world is now at risk and is likely to remain at risk for the foreseeable future.

How we deal with the Zika pandemic is likely to become a roadmap for future challenges.

This work is part of a supplement written by Anthony S. Fauci, M.D., and David Morens, M.D., and sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH). All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.