Wikimedia Commons // Public Domain
Wikimedia Commons // Public Domain

7 Questions About the Zika Virus, Answered

Wikimedia Commons // Public Domain
Wikimedia Commons // Public Domain

In just a few weeks, the Zika virus has gone from relative obscurity to a major concern of the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), and other giants in global disease control. What’s happening with Zika, and why has it exploded now?


Zika is a virus transmitted by mosquitoes. It’s in the same family as several other mosquito-borne viruses that also can cause human disease, including yellow fever, dengue, and chikungunya. There is no treatment or vaccine available.


Most people who are infected with Zika virus don’t even know it; as many as 80 percent of the cases are asymptomatic. For those who do show symptoms, fever, headache, rash, and joint and muscle aches are the most common signs of infection.


Zika is an arbovirus—a virus that is “arthropod-borne.” It is transmitted by mosquitoes—most commonly a mosquito called Aedes aegypti. This mosquito lives mainly in tropical areas of the world, including parts of the United States. A. aegypti is well-adapted to live with humans, laying eggs in stagnant water that can be found around homes—old tires, bird baths, cans, or pots. They feed almost exclusively on humans and can be day-biters, so some interventions to keep mosquitoes away, such as bed nets, aren’t as helpful. They also travel well and can spread via boats or potentially airplanes that move around the world.

While A. aegpyti is the main vector for Zika, there is concern that other mosquitoes may be able to transmit the virus. Another invasive mosquito, the Asian tiger mosquito (Aedes albopictus) is a common disease vector. It can spread viruses related to Zika, and was the main vector of a large Chikungunya outbreak in 2006. This mosquito also was involved in a Zika outbreak in Gabon in 2007, but that was a different strain of Zika than the one currently circulating in the Americas. Researchers in Brazil are also testing the possibility that another mosquito species of the Culex family could spread Zika. While A. aegypti is geographically limited, A. albopictus and various species of Culex mosquitoes are more widely distributed, living in colder climates.

Human-to-human transmission is also theoretically possible. There are two reports of Zika virus transmission via sex. One report involved an American who had contracted Zika in Senegal and developed symptoms upon his return to Colorado, and whose wife developed Zika infection after exposure. A second case found Zika virus in the semen of a man in Tahiti long after the virus had been cleared from the blood. However, even if this is possible, it seems to be a rare mode of transmission.


We’ve known about Zika since 1947, when it was discovered in a monkey in the Zika forest in Uganda. A year later, the virus was found in a mosquito in the same location, and blood samples from humans showed antibodies to Zika, evidence they had previously been infected with the virus. The first documented human case was identified in Nigeria in 1968. Blood testing in the 1950s and 1960s showed infection with the virus was widespread in humans across Africa and many parts of Asia. The first outbreak of Zika outside of Africa or Asia was on Yap Island in 2007, infecting almost 75 percent of the island’s population of 6900 people. A second outbreak in French Polynesia in 2013–2014 may have infected as many as 19,000 people.


Zika first appeared in Brazil in mid-2015, possibly introduced from French Polynesia during 2014’s World Cup soccer tournament or other international sporting events. Active transmission of the virus has been confirmed in 22 countries as of January 28. Many of them are popular travel destinations.

Because they are tourist spots, individuals infected during travel have returned home, incubating the virus. Travel-associated cases have been diagnosed in Denmark, Spain, Portugal, Italy, and the United Kingdom. The United States has seen approximately a dozen cases of imported Zika infections. No local spread has been documented in these countries. The WHO has suggested the outbreak could eventually affect up to 4 million people; approximately 1 million have already been infected.


First, the outbreaks are very large and have infected large proportions of the population where they’ve occurred. Because this virus has never been identified in this geographic location before, the population has no immunity to it—meaning everyone is vulnerable.

In Brazil, there has been an increase in reports of microcephaly in babies. This means that the babies are born with an abnormally small head, and problems with brain development. This has been linked to Zika virus infections in the mother during pregnancy; almost 4000 babies have been diagnosed with the condition since October 2015. A baby born in Hawaii to a mother who had been infected with Zika was also born with microcephaly. As a consequence, the CDC has issued interim guidelines for travel during pregnancy, suggesting that pregnant women do not travel to areas experiencing a Zika outbreak. Other countries experiencing outbreaks have suggested that women delay pregnancy for months or years, until the outbreak subsides—a difficult proposition in an area where many pregnancies are unplanned and access to birth control is limited.

Increases in another neurological condition, Guillain-Barré syndrome, has also been reported in Colombia, and that is thought to be due to Zika virus infections. Though microcephaly has not been reported in association with previous Zika outbreaks, Guillain-Barré syndrome was identified in the 2013 outbreak in French Polynesia.


A lot. Right now, there appears to be a correlation between microcephaly and Zika infection, but we can’t be 100 percent sure that Zika is causing it—or that there really is an increase in microcephaly cases at all. If Zika is indeed causing microcephaly (and/or Guillain-Barré syndrome), we have no idea how the virus is doing this. Assuming the virus is responsible, we don’t know if infection needs to be in a certain developmental window during the pregnancy, or if the infection would have to be symptomatic in order for microcephaly to result. We have no vaccine or treatment for Zika, though the outbreak has spurred interest in developing them. For now, control efforts are concentrated on mosquito elimination and education of the population about the potential risks of infection.

Emery Smith
Stones, Bones, and Wrecks
The 'Alien' Mummy Is of Course Human—And Yet, Still Unusual
Emery Smith
Emery Smith

Ata has never been an alien, but she's always been an enigma. Discovered in 2003 in a leather pouch near an abandoned mining town in Chile's Atacama Desert, the tiny, 6-inch mummy's unusual features—including a narrow, sloped head, angled eyes, missing ribs, and oddly dense bones—had both the “It's aliens!” crowd and paleopathologists intrigued. Now, a team of researchers from Stanford University School of Medicine and UC-San Francisco has completed a deep genomic analysis that reveals why Ata looks as she does.

As they lay out in a paper published this week in Genome Research, the researchers found a host of genetic mutations that doomed the fetus—some of which have never been seen before.

Stanford professor of microbiology and immunology Garry Nolan first analyzed Ata back in 2012; the mummy had been purchased by a Spanish businessman and studied by a doctor named Steven Greer, who made her a star of his UFO/ET conspiracy movie Sirius. Nolan was also given a sample of her bone marrow; his DNA analysis confirmed she was, of course, human. But Nolan's study, published in the journal Science, also found something very odd: Though she was just 6 inches long when she died—a typical size for a midterm fetus—her bones appeared to be 6 to 8 years old. This did not lead Nolan to hypothesize an alien origin for Ata, but to infer that she may have had a rare bone disorder.

The current analysis confirmed that interpretation. The researchers found 40 mutations in several genes that govern bone development; these mutations have been linked to "diseases of small stature, rib anomalies, cranial malformations, premature joint fusion, and osteochondrodysplasia (also known as skeletal dysplasia)," they write. The latter is commonly known as dwarfism. Some of these mutations are linked to conditions including Ehlers-Danlos syndrome, which affects connective tissue, and Kabuki syndrome, which causes a range of physical deformities and cognitive issues. Other mutations known to cause disease had never before been associated with bone growth or developmental disorders until being discovered in Ata.

scientist measures the the 6-inch-long mummy called Ata, which is not an alien
Emery Smith

"Given the size of the specimen and the severity of the mutations … it seems likely the specimen was a pre-term birth," they write. "While we can only speculate as to the cause for multiple mutations in Ata's genome, the specimen was found in La Noria, one of the Atacama Desert's many abandoned nitrate mining towns, which suggests a possible role for prenatal nitrate exposure leading to DNA damage."

Though the researchers haven't identified the exact age of Ata's remains, they're estimated to be less than 500 years old (and potentially as young as 40 years old). Genomic analysis also confirms that Ata is very much not only an Earthling, but a local; her DNA is a nearest match to three individuals from the Chilote people of Chile.

In a press statement, study co-lead Atul Butte, director of the Institute for Computational Health Sciences at UC-San Francisco, stressed the potential applications of the study to genetic disorders. "For me, what really came of this study was the idea that we shouldn't stop investigating when we find one gene that might explain a symptom. It could be multiple things going wrong, and it's worth getting a full explanation, especially as we head closer and closer to gene therapy," Butte said. "We could presumably one day fix some of these disorders."

Just Two Cans of Soda a Day May Double Your Risk of Death From Heart Disease

If you've been stocking your refrigerator full of carbonated corn syrup in anticipation of warmer weather, the American Heart Association has some bad news. The advocacy group on Wednesday released results of research that demonstrate a link between consumption of sugary drinks—including soda, fruit juices, and other sweetened beverages—and an increased risk of dying from heart disease.

Study participants who reported consuming 24 ounces or more of sugary drinks per day had twice the risk of death from coronary artery disease of those who averaged less than 1 ounce daily. There was also an increased risk of death overall, including from other cardiovascular conditions.

The study, led by Emory University professor Jean Welsh, examined data taken from a longitudinal study of 17,930 adults over the age of 45 with no previous history of heart disease, stroke, or diabetes. Researchers followed participants for six years, and examined death records to determine causes. They observed a greater risk of death associated with sugary drinks even when they controlled for other factors, including race, income, education, smoking habits, and physical activity. The study does not show cause and effect, the researchers said, but does illuminate a trend.

The study also noted that while it showed an increased risk of death from heart disease, consumption of sugary foods was not shown to carry similar risk. One possible explanation is that the body metabolizes the sugars differently: Solid foods carry other nutrients, like fat and protein, that slow metabolism, while sugary drinks provide an undiluted influx of carbohydrates that the body must process.

The news will likely prove troublesome for the beverage industry, which has long contended with concerns that sugary drinks contribute to type 2 diabetes and tooth decay. Some cities, including Seattle, have introduced controversial "soda tax" plans that raise the sales tax on the drinks in an effort to discourage consumption.


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