Zika virus’ status as a global health threat may officially be over, but the disease’s impact is far from contained.
The World Health Organization decided in November to end its designation of Zika virus as a public health emergency, but that doesn’t mean that Zika virus has disappeared, explained Dr. Carlos Pardo-Villamizar, a clinical neurologist with an expertise in infectious disorders at Johns Hopkins Medicine.
Alongside pressing concerns about how to prevent a resurgence of the disease, health care systems in Brazil and other countries that saw births of babies infected with the disease in utero now have to find a way to fund and facilitate expensive, intensive therapy and care for thousands of children who have been born with birth defects. As the WHO itself acknowledged, the outbreak will remain a “significant public health challenge.”
And regions of the world that dodged a large Zika virus outbreak in 2016 are still at risk for them in 2017, said Pardo-Villamizar, because the Aedes aegypti mosquito has not been eradicated. This includes other Central and South American countries that didn’t see many infections, countries in Asia that regularly experience dengue outbreaks and the southern region of the U.S.
Dr. Thomas Frieden, director of the U.S. Centers for Disease Control and Prevention, says the U.S. still has a lot of work to do when it comes to controlling Zika virus, protecting pregnant women from the disease and conducting basic research on how the virus works, spreads and hurts those it infects. Pockets of the U.S. that harbor the Aedes aegypti mosquito that spreads the virus continue to have mini-outbreaks, leading the CDC to issue travel warnings about those regions for pregnant women.
Currently, new infection numbers are down due to colder temperatures (and thus, less hospitable environments for mosquitoes), but countries that experienced the biggest outbreaks last year have to deal with the aftermath of those infections, while countries that didn’t experience outbreaks could find that it’s their turn to grapple with a Zika outbreak as temperatures warm.
And Zika virus’ ability to spread sexually ― unique among mosquito-borne viruses ― has transformed men and women into vectors for the disease, which means it can persist even through the colder months when mosquitoes usually die out.
Here are some of the ways that Zika virus will remain a global health problem:
1. Brazil must now provide extra health care services to babies born with Zika virus congenital syndrome.
Brazil, which was hit hardest by births affected by Zika, has seen 1,749 babies born with either microcephaly or other central nervous system birth defects as of late July. The CDC estimates that adequate care for each child affected by congenital Zika virus syndrome will cost between $1 million and $10 million, but it’s unclear how Brazilian families, most of them concentrated in the poorest regions of the country, will be able to come up with these resources.
Babies born with congenital Zika virus syndrome may need physical therapy, treatment for seizures, feeding tubes, eyeglasses and other medical services to help them and their parents cope with symptoms.
And while microcephaly, or an unusually small head, has become a telltale sign of Zika infection in the womb, not all babies born to mothers with Zika virus will show obvious physical evidence of a birth defect. A November study found that babies of mothers who had Zika during pregnancy can develop microcephaly or other brain damage in the months after birth, and researchers anticipate that the effects of the virus on developing fetuses won’t be fully understood until years later, when these children are evaluated for mental illness and learning disabilities in early childhood.
“The lasting effect of the infections that have taken place in utero are going to stay with us for years as these kids grow up,” said Nikos Vasilakis, an assistant professor of pathology and an expert on zoonotic viruses like Zika at the University of Texas Medical Branch.
2. While Brazil has been hit hardest by the epidemic, other countries have affected babies, too.
Colombian scientists confirmed in December that their country experienced a significant increase in microcephaly since the Zika outbreak in 2016. The report confirms that countries that had a widespread Zika virus outbreak should expect a significant increase in congenital birth defects, especially the neurological ones associated with Zika virus congenital syndrome.
Specifically, from Jan. 31 to mid-November, Colombia recorded 476 cases of microcephaly, which is a four-fold increase in cases from the same time period in 2015. July 2016 in particular was a peak month for microcephalic births and miscarriages, and saw a nine-fold increase in microcephaly compared to July 2015. Before this report, health experts were looking hopefully to Colombia for a sign that perhaps Zika virus did not have to go hand in hand with devastating birth defects, as it appeared to do in Brazil. But while the country didn’t see an explosion of microcephalic births linked to Zika virus as Brazil did, Colombia did record an increase in miscarriages. Colombian women may have also delayed pregnancy or sought abortions in higher numbers than Brazilians, as Colombia’s abortion laws are more lenient.
Colombians began contracting Zika virus in October 2015, and the country experienced a peak of infections in early February, reports Stat, but the country declared its epidemic over by July. This could mean that Colombia may yet experience another wave of births or miscarriages affected by congenital Zika virus syndrome, says Pardo-Villamizar.
3. Dozens of babies in the U.S. have been born with Zika virus-related birth defects.
According to a CDC report published in December, 34 babies have been born in the U.S. with birth defects linked to the Zika virus, which include things like microcephaly, brain damage and deformities, excess brain fluid, deafness, eye problems and nerve and joint conditions. In total, 1,246 pregnant women in the U.S. have tested positive for a possible Zika virus infection, which means that the country can expect more babies with Zika virus congenital syndrome to be born in the coming months.
4. Expect small, sporadic Zika virus outbreaks in the U.S. from here on out.
Since late November, Texas has recorded six cases of Zika virus that officials suspect were transmitted by local mosquitoes instead of mosquitoes the patients encountered through travel. This is an important distinction because it means that a local mosquito population in the U.S. appears to have the virus and is now passing it to U.S. residents. The first local case was announced Nov. 28, and health officials found four other cases after going door to door near the neighborhood where the first patient lived.
In response, the Texas Health and Human Services Commission has expanded indefinitely the Medicaid benefit for mosquito repellant for residents in Cameron County. And the CDC issued a travel advisory for Brownsville, Texas, as it did in August for several Miami Beach neighborhoods in Florida. The travel warning recommends that pregnant women, women of reproductive age and their partners get tested for Zika if they were in Brownsville on or after Oct. 29.
A small local outbreak at the southernmost tip of Texas is no surprise (experts predicted both this cluster and the Florida cluster back in January), but it does show that certain U.S. neighborhoods, especially those with prior outbreaks of other mosquito-borne diseases, are vulnerable to Zika.
“You should expect to see a repeat of what we have seen with West Nile virus, dengue and Chikungunya when they were introduced in the continental United States,” Vasilakis explained. “Basically you’re going to have very focal epidemics that are self-limited and burn out.” This is because the U.S.’s higher standard of living, which includes widespread use of air conditioning units and window screens, cuts down on people’s exposure to mosquitoes.
5. We still don’t have a vaccine or cure for Zika virus, and we need one badly.
Zika virus remains without a cure, but there is hope that an effective vaccine will emerge in just a few short years. While it normally takes 10 years to develop a new vaccine, experts estimate that a vaccine for Zika virus could be ready in two years, reports The New York Times. This is partly because so many different companies and government agencies are trying to be the first to create a safe, effective and scalable vaccine that can protect people, and especially pregnant women, from getting the disease.
The National Institute of Allergy and Infectious Diseases, for instance, is working on four different vaccines, all in various stages of development, to see if one can prevent Zika virus infection. Two of the vaccines are still in the preclinical research stage, but in November, NIAID announced the first of five clinical trials to test one of these vaccines, made with inactivated Zika virus, in a group of 75 people who have never had any type of flavivirus before. Another NIH vaccine candidate, based on research for a West Nile vaccine, is scheduled to begin phase 2 clinical trials in Zika-endemic areas in early 2017.
Although research on Zika virus vaccines has surged, little funding for research is focused on the basic concepts of the virus, or on anti-viral treatments for the disease, says Pardo-Villamizar, who is involved in Latin American studies of Zika virus and Guillain-Barre syndrome.
“Despite the fact that some money was dedicated to Zika research, mostly oriented to the public health measures U.S. is taking, there is need for additional funding for improving the research capability of viral infections like Zika,” he said. “Developing antiviral medications and understanding pathogenesis of the disease is extremely important and needed, and the funding is basically negligible.”
“There are a lot of unanswered questions that need to be answered,” he said. “What are the effects of symptomatic versus asymptomatic infection? What are the long-term effects in humans? What is the contribution of sexual transmission of Zika in the overall scheme of virus transmission?”
“We are trying to understand as much as we can about this virus, but it’s not going to be a one-inning fight.”