New Zika Research Highlights Potential Concerns as Mosquito Season Begins: Public Health Watch

Zika virus may be gone—at least from the continental United States—but it is far from forgotten.

Indeed, just as mosquito season is set to begin here in North America, newly published research suggests that the virus is still a viable threat to public health, and that its precise effects on those infected remain largely unknown or at least up for debate. In fact, there are some who believe that the world is no closer to fully understanding Zika and, thus, preparing for future outbreaks.

For example, a study published on May 10 in The New England Journal of Medicine highlights a good news/bad news proposition with regard to screening blood supplies for Zika virus. The authors, affiliated with the American Red Cross, screened blood provided by more than 4.3 million donors to the organization’s blood banks over a 15-month period in 2016-2017 for Zika virus RNA using transcription-mediated amplification (TMA). Reactive donations underwent “confirmatory testing” via repeat TMA, real-time reverse-transcriptase polymerase chain reaction, IgM serologic testing, and red-cell TMA, among other methods. In all, more than 3.9 million donations were tested individually for Zika, and 160 were initially reactive and 9 were confirmed positive. Of these, 2 had been transmitted locally (in Florida), 6 had traveled to Zika-active areas, and 1 had received an experimental vaccine for the virus.

The bad news? The authors concluded that screening blood supplies was “costly” given the “low yield.” For the donations screened, the cost of individual-unit nucleic acid testing was $5.3 million per Zika-positive donation. Overall, the cost of Zika testing was approximately $41.7 million over the course of the 15-month study. As the American Red Cross collects 42% of the US blood supply, according to data provided to the authors, the projected annual cost for national screening is estimated to be $137 million, which, they note, “will pose an additional strain on the blood industry,” and may thus make screening for Zika cost-prohibitive.

Another study, published May 15 in BMC Medicine, focused on the risk for Guillain—Barré syndrome (GBS) among those with Zika virus infection. In the years since the Zika outbreak in Brazil in 2014, there has been much debate within the scientific community about a potential “causal link” between the virus and the neurological syndrome.

The authors reviewed more than 330,000 confirmed Zika cases from 11 regions in South America and the Caribbean and, using a mathematical model, estimated that 2.0 reported GBS cases may occur per 10,000 Zika virus infections, although they acknowledged that their findings likely raise more questions than answers, given the variability in the number of GBS cases among the 11 locations included in the analysis. Interestingly, another recent study, published May 21 in JAMA Neurology, looked at GBS in 123 patients both with and without Zika and found that those with the neurological condition and the mosquito-borne virus were more likely to experience symptoms such as facial weakness, facial paresthesia, dysphagia, shortness of breath, elevated protein levels in cerebrospinal fluid, and severe pain.

However, despite these findings, Leonelo E. Bautista, MD, MPH, DrPH, associate professor, department of Population Health Sciences, University of Wisconsin, who has published extensively on Zika and has argued that a causal relationship between the virus and GBS has yet to be adequately demonstrated told Contagion^® that he remains skeptical of study findings linking the 2 conditions.

In a paper he co-authored, which was published on May 24 in BMC Public Health, he noted that virus current surveillance guidelines, developed based on a causal relationship between Zika, GBS, and microcephaly (a birth defect that has been linked with the virus), “have a low probability of detecting outbreaks” of the 3 conditions, and “could result in significant increases in health care burden, due to the detection of large numbers of false positive[s].”

“In a nutshell, current evidence does not support a causal link between Zika and GBS or Zika and microcephaly,” Dr. Bautista said. In his view, then, “the public health response to Zika was premature, supported by questionable casual links, and with little support from existing data and scientific knowledge.

“In terms of health and well-being, the public health response to Zika may have been more harmful than beneficial, particularly for the population of Latin America,” he added.

A sobering thought for regions still considered at high risk for Zika outbreaks—and/or those traveling to these areas. As reported by the World Health Organization, there was a small Zika outbreak in India last year, and officials there remain concerned about future cases. And the US Centers for Disease Control and Prevention still considers much of South America, Africa, and Southeast Asia as areas with elevated risk for the virus.

We’ll see what this summer has in store…

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous health care-related publications. He is the former editor of Infectious Disease Special Edition.