How Zika Evolved

A study published this week in the journal Science may finally give some answers as to why the Zika outbreaks in 2016 have caused major brain abnormalities in more than 3,500 babies born across the Americas. Researchers have identified a tiny mutation in this mosquito-borne virus that may have transformed it from a minor annoyance to a serious public health threat.

Zika virus is not new — it was named for Uganda’s Zika Forest, where it was discovered in 1947. There have been outbreaks across Africa and Asia in the decades since, but most were not notable because those who contracted the virus had mild, flu-like symptoms and no long-term health issues. But when it hit Brazil in 2014, it became apparent that something had changed as the virus seemed to bring with it an increase in microcephaly, a once-rare condition in which babies are born with small heads and underdeveloped brains. (The U.S. Centers for Disease Control and Prevention officially declared Zika the cause of these cases of microcephaly in April 2016.)

Science had paid very little attention to the Zika virus until that point, and researchers were suddenly sprinting to find out all they could about it so that they could determine how to test for it, treat it and most importantly, prevent it from spreading rapidly.

Researchers in China, who published this most recent study, wanted to understand if the virus had always had the potential to cause birth defects in developing fetuses and the numbers were just too small for us to have noticed until now, or if something was different about the virus itself. After all, viruses mutate all the time in an effort to get stronger and multiply faster.  

To identify any mutations, researchers compared samples of the virus taken from patients in the current outbreak to samples collected during a 2010 outbreak in Cambodia not linked to birth defects. They identified seven changes in the structure of the virus and then made a series of clones of the virus that each had only one of these changes. These man-made viruses were then given to pregnant mice.

They found that one of the versions — which contained a change to a single amino acid — was most destructive. When they compared this strain to the 2010 strain, they found that it multiplied faster and killed more brain cells. 

These findings give researchers a greater understanding of the virus and may help efforts to develop vaccines and screening tests. For example, the lead author of the study suggests that any live-virus vaccines that are tested in humans would be safer if they use a version of the virus that has removed this mutation. In addition, future blood tests may be more accurate if they look for this specific mutated protein. Current tests are missing some cases of Zika and turning up false-positives in people who have been exposed to other mosquito-borne infections.

While our scientific understanding of the virus is increasing, as of now, the day-to-day advice for women who are pregnant or planning to become pregnant has not changed. If you’re worried about Zika virus, prevention is your best bet. Here’s how you can protect yourself: 

  • Be cautious about travel. If possible, avoid travel to regions most affected by the outbreak including South America, Mexico, Cuba and Puerto Rico as well as much of Africa. In the United States, Zika is most common in parts of Texas and Florida. 
  • Protect yourself from mosquitoes. Try to prevent mosquito bites by wearing long pants and long-sleeved shirts outside, using mosquito repellent, staying inside at dusk when mosquitoes are most active, and sleeping in a room with air conditioning or window screens whenever possible.
  • Practice safe sex. If you or your partner have recently traveled to a Zika-affected area, consider waiting six months before trying to conceive. If you are pregnant, use condoms or dental dams or avoid sex for the duration of your pregnancy. 
  • Get tested if you show symptoms. The CDC no longer suggests that all pregnant women be tested, but if you are pregnant and live in or travel to Zika-impacted areas, you should get tested as soon as possible if you have any symptoms such as headache, rash, red eyes, pain behind the eyes or joint pain.


Why Is It So Hard to Get Tested for Zika?

How Close Are We to a Zika Vaccine?

CDC Issues New Zika Testing Guidelines for Pregnant Women

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