The ability of the United States to respond to a potential spike in Zika virus infection rates is a cause for concern, according to a top federal health official.
“The big question is will we get local transmission, and my response to that is very likely we will,” Dr. Anthony Fauci, director of the National Institute of Allergies and Infectious Diseases, told reporters during a joint media briefing with the Pan American Health Organization (PAHO) on May 3.
As many as 500 million people in the Americas are at risk for being infected by the Zika virus, PAHO’s Zika incident manager, Dr. Sylvain Aldighieri, said during the briefing .
In the continental United States to date, there have been about 400 travel-related cases of infection. In Puerto Rico, there have been nearly 700 locally reported cases , and one Zika-related death.
Countries at highest risk for Zika include those that have experienced any outbreaks of dengue fever or chikungunya in the past 15 years, Dr. Aldighieri said. Hawaii and U.S. territories in the Caribbean have experienced local dengue outbreaks during that time. Florida has had local outbreaks of both illnesses.
In the United States, Zika is poised to gain a stronger foothold even as funding for the study and prevention of the virus remains stalled in Congress, and a lack of cohesive public health messaging leaves the public vulnerable to misunderstanding the potential threat of the disease, according to Dr. Fauci .
A vaccine to fight Zika virus is currently under development. “Don’t confuse that with readiness,” Dr. Fauci cautioned.
Dr. Fauci said he believes the disbursement by Congress of President Obama’s requested $1.9 billion in Zika-related funds would facilitate a more comprehensive approach to preventing and treating the virus’s spread, but so far, the funding remains stalled.
As a result, Dr. Fauci said he has reallocated funds intended for other infectious disease research needs to cover Zika-related costs, but is concerned that continued congressional inaction could mean he is left with holes across many budgets. “That 1.9 billion dollars is essential,” he said.
Vaccine progress
In April, $ 589 million in funds primarily earmarked for the Ebola crisis were redirected by the Obama administration to fight the Zika virus. That money is now being used in part to fund development of a vaccine that is expected to be ready for a phase I study of 80 people by September 2016. If successful, a phase II-b efficacy study of the vaccine would be conducted in the first quarter of 2017 in a country or region that has a high rate of infection.
Dr. Fauci said that although the study is not be as high-powered as would be ideal, researchers might be able to determine the vaccine’s efficacy with several thousand volunteers, taking into consideration that during the 1-3 years needed to gather conclusive data, herd immunity could skew rates of infection downward, bringing into question the vaccine’s actual efficacy.
“That’s just something we have to deal with,” Dr. Fauci said, saying that fewer people being infected is a good thing, either way.
Research gaps
Other pressing Zika research needs to include learning more about the virus’s impact on a developing fetus.
“We don’t know exactly what the percentage is of [infants born with] microcephaly,” Dr. Fauci said. “We don’t know beyond microcephaly what the long-range effects are on babies that look like they were born [without microcephaly] but might have other defects that are more subtle.”
Dr. Fauci said current data are unhelpful in that they show anywhere from 1% to 29% of infected mothers will give birth to children with congenital defects. However, he said that a coalition of nations affected by the virus is currently enrolling thousands of pregnant women in a cohort study to determine risk ratios.
“When we get the data from that study, we will be able to answer precisely what the percentage is, but today in May 2016, we don’t know the answer,” he said.
Predicting which infants are most susceptible, and at what point in utero abnormalities develop, are questions still under investigation, although a study published earlier this year supports the theory that infection during the first trimester poses the highest risk to a developing fetus.
Communicating risk
Another problem facing health officials is how to communicate the potential seriousness of an illness that, if it presents at all, does so only mildly, Dr. Fauci said. “In general, it’s a disease in which 80% of people don’t have any symptoms.”
The World Health Organization advises physicians to suspect Zika – particularly if a person has been in Zika-affected regions – if clinical symptoms include rash, fever, or both, plus at least one of these: arthralgia, arthritis, or conjunctivitis. Aside from bed rest, hydration, and over-the-counter analgesics, there are no specific treatments for the virus.
How to counsel women about avoiding pregnancy where Zika is a concern also poses challenges, particularly if the pregnancy is unintended, as about half of all American pregnancies are , or if, as Dr. Fauci told reporters, pregnancy is “guided by laws and religion.”
Although federal policy has not been to advise persons about whether to delay pregnancy, Dr. Fauci said U.S. officials are unwilling to contradict authorities in local regions such as Puerto Rico where such statements have been issued.
On April 28, the Food and Drug Administration authorized the emergency use of a commercial in vitro diagnostic test for use in individuals with symptoms of the virus, or those who have traveled to affected regions. Earlier this year, the FDA granted emergency authorization for use of a single test that can detect Zika, dengue, and chikungunya. Still, serology tests for Zika are often inconclusive, since the virus can mimic dengue or chikungunya, according to Dr. Aldighieri. “It can be complex to know if there is a Zika or dengue or chikungunya outbreak,” he said.
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