The outbreak of Zika virus in the Americas is “the most complicated health emergency” the U.S. Centers for Disease Control and Prevention has ever handled, said a top senior federal official Tuesday at a special Zika press briefing organized by the ASTMH leadership for the 2016 Annual Meeting.
“We have never had a mosquito-borne virus that can cause birth defects,” said Anne Schuchat, MD, the CDC’s Principal Deputy Director. “We have never had a mosquito-borne virus that can be spread sexually. We don’t have a great track record with controlling Aedes aegypti (the mosquito that carries Zika). And we have an unprecedented frequency of people traveling to every part of the world and back. ”
Schuchat led off a panel of experts who are confronting all aspects of an outbreak that is confounding some the best minds science. ASTMH President Stephen Higgs, PhD, director of the Biosecurity Research Institute at Kansas State University and an expert in mosquito-borne diseases, played a key role in organizing the briefing, . which was moderated by ASTMH Executive Director Karen Goraleski.
Higgs said the 4300 attendees at this year’s Annual Meeting “probably have more combined expertise related to Zika than anywhere else in the world; it’s truly unequaled.” He noted that society members can be found “serving in the field,” tracking the disease and assessing its consequences, and working in the laboratory to develop new ways of treating, diagnosing and preventing Zika.
“We also have not been silent about concerns over funding,” Higgs said. He pointed out that earlier this year, the society took the unusual step of drafting a letter signed by 22 current and former ASTMH presidents urging members of the U.S. Congress to adequately fund the fight against Zika.
Higgs and other experts on the panel were unanimous in their assessment that the Zika outbreak is a major challenge.
“I have never seen anything similar to this Zika virus epidemic in my 35 years of infectious disease practice,” said Pedro Fernando da Costa Vasconcelos, MD, PhD, director of Brazil’s Evandro Chagas Institute. Vasconcelos has been grappling with a number of mysteries, including why the high rates of microcephaly tied to the Zika outbreak in northeastern Brazil are not being recorded in other areas experiencing high rates of infections.
He said that in addition to the fetal risk, he is also concerned about the potential for high rates of severe disease in people with auto-immune disorders like lupus. And he is worried about a new wave of Zika outbreaks hitting Brazil. Thus far, most of the infections in Brazil have been in the northeast of the country. But Vasconcelos said he also is concerned about outbreaks hitting large population centers in the south, chiefly Sao Paolo and Rio de Janeiro.
Vasconcelos’ colleague Albert Ko, MD, an infectious disease expert at Yale School of Public Health and a collaborating researcher with the Brazilian Ministry of Health, said there is reason to fear that Zika is capable of causing several types of birth defects, not just microcephaly. Ko said there is also evidence of infants born with lesions that affect hearing and sight.
“There is an enormous amount of fear among pregnant women,” Ko said.
Ko acknowledged that studies in different patient groups have led to a wide range of estimates for the rate of microcephaly tied to Zika infections. He said he hopes in the near future there at least will be a test for women who live in areas where the disease is common that would show whether they were already exposed to the Zika virus, which often causes very mild symptoms that can go unnoticed. Such an exposure could mean that they have developed immunity, Ko said, and can “safely become pregnant.”
Ivan Gonzalez, MD, a pediatric infectious disease specialist and co-director of the Zika Response Team at the University of Miami Health System, said pregnant women in his practice are understandably nervous. But he said the process for testing for the Zika virus has at least been shortened, down from four to six weeks to seven to ten days.
For any women who give birth after being infected with Zika, Gonzalez said that triggers the Zika response team and “we do a huge workup and are prepared to follow these babies for a very long time.”
ASTMH Councilor Ann Powers, Chief of the Alphavirus Laboratory with the CDC’s Division of Vector-Borne Diseases, said it’s especially important to have tests that can distinguish Zika from dengue. The two viruses are closely related and some of the existing tests for Zika routinely have had trouble distinguishing one from another.
“It is very critical to have something that is fast and also very specific,” she said. “We are concerned that if there is a large outbreak of dengue, will that look like a large population infected with Zika?”
Peter Marks, MD, PhD, Director of the Center for Biologics Evaluation and Research at the U.S. Food and Drug Administration (FDA), said FDA is committed to “regulatory flexibility” and already has used its emergency authority to expedite approvals for new Zika diagnostic tests. He said the agency also is prepared to expedite approvals of new drugs or vaccines for Zika and assisting efforts to screen blood supplies to ensure Zika infections are not transmitted via infusions.
One reporter wondered whether there will still be large populations experiencing significant outbreaks of Zika by the time there is a vaccine is ready for testing. Conventional late stage vaccine trials typically seek to determine whether a candidate can protect a large group of volunteers who are at of infection. Marks said FDA would consider alternate approaches to testing vaccine efficacy, and is committed to ensuring vaccine development progresses even if there is a pause in Zika outbreaks.
But he said he doubts there will be a pause.
“I tend to agree with (the CDC’s Schuchat) that we will continue to have plenty of opportunities to test vaccines,” he said, noting that unfortunately, Zika is unlikely to fade away anytime soon.
Ko said many Zika experts are keeping a nervous eye on large population centers in Singapore, Thailand, and Vietnam, countries where Zika has been detected and where there are concerns that major outbreaks could occur.