Francesca Tomasi received her B.A. from the University of Chicago and is now a microbiologist.
This is the story of a virus. For now, we’ll call it Virus X. You will see why.
Virus X caused a mild disease. People who caught it rarely got seriously ill. They usually developed a rash and some malaise with a low fever. Sometimes some joint soreness occurred too, but within a week everything returned back to normal. Doctors and researchers knew what Virus X was because it spread in many places around the world. And while they didn’t have a grasp on the specific biology of the virus, the disease was self-limiting and mild enough that nobody considered it a serious threat.
Virus X usually occurred in geographical clusters; an outbreak here, and outbreak there. One year, a Virus X pandemic broke out. People were becoming infected left and right. It was no big deal, though: nobody died, and everyone recovered.
Suddenly, however, something strange began to happen. Women were reporting miscarriages, stillbirths, and babies born with neurological deficits at alarming rates. It soon turned out that these women had been infected with Virus X at some point during their pregnancy; somehow, Virus X had crossed the placental barrier from mother to fetus.
The story of Virus X has been told twice so far in modern history. The first version unfolded in the mid-1960s in the United States. Rubella is an acute, highly contagious viral infection that causes generally mild illness in children and adults. It often causes a characteristic rash and clears in 7-10 days. During a rubella pandemic in 1964, however, about 50,000 women were exposed to the virus while pregnant. At least 20,000 babies were born with a condition now called congenital rubella syndrome (CRS), which causes blindness, deafness, brain and heart damage in newborns. Within a decade, a vaccine for rubella entered the market, putting an end to the tragic pregnancies. Now, almost every child is vaccinated at a young age with the MMR vaccine, which gives more than 95% long-lasting immunity. Outbreak clusters still pop up every so often in vaccine-administered regions due to suboptimal vaccination rates, but overall rubella has been eliminated wherever the vaccine is administered. The WHO aims to achieve rubella elimination (along with measles; the MMR vaccine covers both diseases) in at least 5 WHO regions by the end of 2020.
Virus X struck again in 2015 and is causing an ongoing pandemic across North and South America. This time, the culprit’s real name is Zika. The virus was discovered around the same time as rubella, though in completely different regions. Whereas rubella was discovered in Europe, Zika was isolated in the Zika forest of Uganda. Zika is not nearly as contagious from person-to-person as rubella; rubella spreads via airborne droplets from people coughing and sneezing. Zika spreads mainly through the airborne nuisances we call mosquitoes (now, there’s also talk of sexual transmission). Like rubella, Zika virus causes very mild symptoms, if any. Infected individuals may get a rash, some soreness and fatigue, and a mild fever. The virus has also been linked to some neurological syndromes such as Guillain-Barre in a small fraction of infected people.
As you probably know, the Brazilian Health Ministry reported at the end of last year a rise in microcephaly cases. Microcephaly refers to abnormally small head sizes encasing an underdeveloped brain. By February 2016, the WHO declared the ongoing Zika virus pandemic to be a Public Health Emergency of International Concern. The last 3 of such declarations occurred in the 2014 Ebola outbreak, a 2014 resurgence of polio, and the 2009 Swine Flu pandemic.
So far, the link between Zika virus and fetal brain damage is suspected, and scientists are working hard to prove it. But rubella and Zika have enough thematic overlaps that the former may hold some clues for us about the latter. Exactly how these kinds of viruses cross the placental barrier from mother to fetus is not yet fully understood. Taking what we know about rubella and combining it with what we know about the viruses that Zika is more similar to genetically – yellow fever virus, for instance – can take us one step closer to figuring out how this barrier breach occurs. This can be done by comparing the structures of rubella and Zika after taking out similarities shared between Zika and other members of its family. Furthermore, timing of infection during pregnancy and additional risk factors that may exist to exacerbate the effects of maternal infection on a developing fetus are still under heavy study.
One thing, though, is for sure: prevention is key. There are several things we can do to reduce Zika infection. Mosquito control of different forms and restricting travel to Zika-rich regions for pregnant women are two that readily come to mind. A third method is arguably the most effective and efficient, though still a ways away in the R&D world: vaccination. If we can come up with a vaccine for Zika virus, we can knock out yet another virus that has implicated in heartbreaking pregnancy outcomes. Living in a developed country today often causes us to take vaccines for granted. An extreme manifestation of this is the emerging “Anti-Vaxxer” movement, where select parents are worried about the scientifically debunked accusations that vaccines cause adverse outcomes in children including severe allergies and autism, and that the risks of vaccines outweigh the benefits. But in countries where infectious diseases are still a major cause of morbidity and mortality, vaccines are administered without second thought to protect people from a young age. And nothing terrible has happened; in fact, quite the contrary! The meningitis belt in sub-Saharan Africa is on its way to eradicate Meningitis A, for one. Now, a new infectious disease is buzzing its way into regions that may not have seen deadly infections since the advent of modern medicine and nation-wide vaccination campaigns. Public reception of the Zika pandemic (and common sense) implies that families will do what it takes to protect themselves, and their future children, from the risk of neurological effects of the virus. A Zika vaccine would be just as altruistic as the rubella one: immunization would be intended to protect future fetuses from infection, and to reduce the potential development of Guillain-Barre in infected adults.
Infectious diseases are nothing new. They have been around since the dawn of life on Earth. Emerging and re-emerging infectious diseases are a developing theme in our modern, highly-interconnected world. Science and history are our strongest weapons as we take on novel – but not unexpected – microbial challenges.