PacSci Perspectives

Zika: A Live Case Study

by | Sep 21, 2016

Learn about the history and evolution of the world’s current mysterious health issue.

It is easy for frightening diseases to feel far away, but one has begun to crop up on our home turf: Zika has shown up in Miami. A mosquito-borne disease known for causing birth defects, the virus is making its way around the globe. Dr. Molly Ohainle, a fellow with Pacific Science Center for almost two years, studies viruses like Zika at the molecular level (pathogenetics). She and her colleague, Dr. Kate Williams (who studies immunology and public health), will speak about the Zika outbreak on September 28, 2016 at our PACCAR Theater. Beginning with a screening of the film Outbreak to help show how a virus like Zika can spread, Drs. Ohainle and Williams will explain why this relatively unstudied virus is so unusual, along with some common misconceptions.

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“Mosquitoes vectors are the driving force behind all Zika epidemics,” Ohnaile says. Hot, humid climates where mosquitoes thrive are at the highest risk; places such as Florida, Brazil and Uganda. Although there are other methods of transmission, including sexual contact and blood transfusions, Ohainle emphasizes these instances are rare; we don’t know “just how frequent or relevant they are.”

Zika is rarely fatal in an adult host. In fact, 75% of cases are asymptomatic. Some infected persons exhibit flu-like symptoms such as fever, skin rash, aching muscles, and vomiting for several days to a week. “The dangers come from getting infected while pregnant, particularly during the first trimester,” Ohnaile explains, when Zika “can cause microcephaly in the fetus.” Babies afflicted with microcephaly have much smaller than average heads because of an underdeveloped brain (cases range from mild to severe). Zika is unusual in that in can transmit in vitro; most mosquito-borne diseases, such as malaria, will not infect a fetus.

Zika was discovered in Uganda in the 1920s, but no one thought it was dangerous. “It was probably transmitted by primates,” says Ohainle, and it was recorded to have spread as far as French Polynesia. Because it was not seen as a threat, however, no one studied it. The large-scale epidemic in Brazil in the 21st century showed unprecedented viral evolution.

How did the virus jump across the Pacific Ocean from Africa to South America? That is a mystery. In order to spread with such ferocity, a virus needs the help of the right host. “It’s rare to see a virus like this spread without the help of mosquitoes,” Ohainle says. It’s unlikely, for example, that Zika spread simply because one human was infected and brought it back home. Was a population of mosquitoes brought over by humans? “The virus probably evolved, in a way we haven’t seen before,” notes Ohainle; however, she emphasizes that viruses don’t evolve as dramatically or as quickly as they do in movies (such as Outbreak). “You won’t see a virus evolve from being transmitted through close contact to being airborne over the course of weeks or even a year,” she says.

There is not yet a vaccine or drug to prevent or treat Zika. The most effective way to combat the virus right now is to combat the mosquitoes. Simple tools like mosquito nets and insecticide can be useful. Some scientists want to genetically modify mosquitoes to not carry the virus. “You’re sort of seeing science happen live right now,” Ohainle says. For example, scientists recently linked Zika almost conclusively to microcephaly. While they were eager to share their findings, “it is rare to find a scientist that will present this as fact, because so much is changing.”

Though colder climates like Seattle don’t harbor large mosquito populations and are unlikely to see large outbreaks of Zika, the study of its viral evolution could benefit us. Learning how this virus evolves and spreads may help us combat the next relatively unstudied disease. What if another virus spreads at such an alarming rate, or can cause birth defects? Paying attention to these health issues, whether they affect us directly or not, contributes to an overall healthier world.