Analyze This: Zika and microcephaly | Science News for Students

Analyze This: Zika and microcephaly

Hoping to learn more about Zika, scientists compared spikes in infections and in a birth defect
Mar 29, 2017 — 6:55 am EST
zika timelag

Zika infections among pregnant women (solid line and scale on left) in the nation of Colombia spiked in January 2016 (around week 4). About six months later, the country saw a drastic increase in the number of infants and fetuses with microcephaly (dotted line and scale on right). 


Zika is a viral disease that humans can contract after being bitten by mosquitoes. It is a very serious problem for pregnant women and their babies. Evidence has been mounting that this virus can cause a birth defect called microcephaly. Babies born with the condition have abnormally small heads and other problems. Scientists at the Centers for Disease Control and Prevention (CDC) and elsewhere have been collecting data on Zika and how it is impacting families.

This graph takes data collected in Colombia on pregnant women, fetuses and infants. Zika has taken a big toll in this South American country. The number of babies born with microcephaly in 2016 there was four times what it was in 2015. In the graph, the rate of pregnant women infected with Zika is shown with a solid line. The rate of infants and fetuses who had microcephaly in Colombia from 2015 to the end of 2016 is shown with a dotted line.

“This provides very compelling evidence that every country that experiences a large Zika outbreak is likely to see devastating outcomes on fetuses and infants,” says CDC epidemiologist Peggy Honein.

Data dive:

How does this graph support what the scientist said?

When was the largest spike in reports of pregnant women with Zika? How many women were diagnosed with the disease?

When was the largest spike in reports of infants and fetuses with microcephaly?

How many weeks apart are these events?

Was this graph difficult to understand? Why?

Is there a way to improve this graph or make it easier to read?

Analyze This! explores science through data, graphs, visualizations and more. Have a comment or a suggestion for a future post? Send an email to

Power Words

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Centers for Disease Control and Prevention     (or CDC) An agency of the U.S. Department of Health and Human Services, CDC is charged with protecting public health and safety by working to control and prevent disease, injury and disabilities. It does this by investigating disease outbreaks, tracking exposures by Americans to infections and toxic chemicals, and regularly surveying diet and other habits among a representative cross-section of all Americans.

epidemiologist     Like health detectives, these researchers figure out what causes a particular illness and how to limit its spread.

infection     A disease that can spread from one organism to another. It’s usually caused by some sort of germ.

microcephaly     A condition that leaves babies with abnormally small heads and partially developed brains.

outbreak     The sudden emergence of disease in a population of people or animals. The term may also be applied to the sudden emergence of devastating natural phenomena, such as earthquakes or tornadoes.

virus     Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.

Zika     A viral disease that can be transmitted to humans via mosquitoes. About 20 percent of infected people get sick. Symptoms include a slight fever, rash and pinkeye and usually fade quickly. A growing body of evidence suggests that the virus could also cause a devastating birth defect — microcephaly. Evidence suggests it may also cause neurological conditions such as Guillain-Barré syndrome.


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Further Reading