For years, the Zika virus was thought to be a mild virus. Yet with recent confirmation that the Zika virus is causing alarming numbers of birth defects and neurological problems in Central and South America, the pandemic has shaped up to be a major public health and ethical challenge.
Zika is a flavivirus, a type of virus related to dengue, west nile virus, and yellow fever. Like its cousins, Zika spreads rapidly through a population.
According to Prof. Laura Harrington, entomology, one of the major barriers to controlling the virus is that it is transmitted by “container-breeding mosquitoes”. Unlike other mosquitoes, the mosquitoes that carry Zika are harder to kill.
“It’s hard to find all the breeding sites, and it’s hard to use insecticide with these mosquitoes,” Harrington said.
The current outbreak is notorious for the rapid emergence of cases of microcephaly, a rare and incurable condition where infants are born with dangerously small heads. Microcephaly can lead to seizures, trouble breathing, eating, and speaking. Early on, it was unclear as to whether a pregnant woman bitten by the mosquito could transmit the virus to the fetus.
Several challenges prevented pinpointing Zika as the true culprit behind massive numbers of birth defects, including the fact that microcephaly was previously not known to be a symptom of Zika.
“When the outbreak started, we did not want to rush to associate Zika with microcephaly if it was not true,” said Dr. Matt McCarthy, assistant professor of medicine and infectious disease specialist at Weill-Cornell/New York Presbyterian Hospital.
Over time, evidence from case reports, animal, cell, and autopsy studies suggested a causal connection between maternal infection with Zika and birth defects. The World Health Organization said the virus is “neurotropic,” more often affecting brain tissue than other tissues. Studies have found Zika virus in fetal brain tissue. Mounting evidence led the Center for Disease Control to recently announce that Zika caused microcephaly.
For physicians, dealing with a new outbreak can be challenging, even in the USA where Zika is not as prevalent as it is in South America.
“At our department of infectious disease at Cornell, in the middle of Manhattan, we had very little experience with Zika — almost none, until this outbreak happened,” McCarthy said. “The next thing we knew, patients were asking us, ‘What’s safe? Can I travel to the Bahamas, or go to the Olympics? What if I’m thinking of becoming pregnant?’ And the truth is, the data was so sparse that we did not really know how to answer people. We like to see robust data — decades worth of data — and we just do not have that yet.”
Prof. Julia Finkelstein, nutritional science, whose research in maternal and child health involves infectious disease surveillance in Ecuador says that a part of the lack of robust data is the “inherent tension” between the time it takes to conduct thorough studies and the need to provide recommendations quickly.
Finkelstein is currently working on a rapid systematic review with colleagues to investigate whether Zika can be transmitted through breastfeeding.
“The normal time it takes for a rapid systematic review is six to 12 months, but this rapid systematic review is set over the course of several weeks,” Finkelstein said. “We are looking at all the evidence to date for Zika virus transmission. WHO is specifically interested in looking at guidelines for mothers who may have been exposed to Zika during pregnancy, and to develop guidelines for breast feeding.”
As of now, experts know that in addition to being transmitted through mosquitoes, Zika can be sexually transmitted and causes microcephaly as well as other birth defects. According to McCarthy, Zika may also contribute to intrauterine growth restriction ( small babies), eye problems, as well as calcified deposits in the brain, which may indicate brain tissue death.
As new evidence emerges, guidelines on Zika change. “I get emails all the time telling me the latest update on what we are supposed to recommend to our patients, and that’s tricky,” McCarthy said, “When someone asks me a question I look at my email and check that nothing has changed.”
Several questions about Zika remain unanswered. This has led to cautious, yet sometimes controversial, recommendations.
“One of the big ethical issues is what to do if you find out your unborn child has microcephaly. The areas hardest hit have some of the most restrictive access not only to abortion but also to birth control,” McCarthy said, “Some countries have told people, ‘Don’t have kids for two years,’ and that is a really hard situation.”
Another ethical issue is whether to use genetically modified mosquitoes to combat transmission of Zika through mosquitoes. For example, one idea is to release modified mosquitoes that are sterile.
“This is a dilemma that we have been talking about in the bioethics world,” McCarthy said, “And these are some of the ethical issues people are going to be tackling in the future”.
Harrington said that while she is not involved at all in releasing genetically modified mosquitoes into the wild, her research does include finding new ways to control them. For example, one of her projects is looking into finding a molecule that may curb female mosquito interest in taking a blood meal.
“There is still a tremendous amount of ethical work that needs to be done to see if it is feasible to release modified mosquitoes,” Harrington said.
Harrington is also investigating geographic variation in the ability of mosquitoes to transmit disease, habitats these mosquitoes breed in, and what factors affect mosquito survival. Such work could have a significant impact on finding new ways to limit the spread of disease-carrying mosquitoes.
“We don’t expect there to be explosive outbreaks in the USA like there are in South or Central America,” Harrington said.
How to communicate public health and disease control efforts, from the country-level to the physician-patient level, is also a major challenge. Trust is central to this effort — both in the USA and in Central and South America.
“Working with the local population to help get past mistrust is really important. In global and public health, we rely on community health workers.” Finkelstein said. “People know their own communities best”.
Current Center for Disease Control and Prevention guidelines for men and pregnant sex partners state that men should abstain from sex during the pregnancy. Day-by-day, however, new research emerges to shape guidelines on the Zika virus.
“We have learned a decent amount, but we still have a ton that we need to learn,” McCarthy said.