Colombian health officials are tracking a cohort of about 2,000 pregnant women who have contracted Zika to see if their babies are born with abnormally small heads, according to the Pan American Health Organization.
Researchers suspect Zika may be related to a surge in microcephaly—a condition where a baby is born with a smaller-than-average head and can have an underdeveloped brain—in Brazil, and are anxiously watching to see if the virus causes spikes in the birth defect in other affected countries, such as Colombia.
As the Zika virus spreads rapidly in Latin America, alarming news stories and photos of children with undersized skulls have also been spreading. The link between Zika and microcephaly has not yet been proven, but Brazil is currently sifting through thousands of reported cases of Zika-related microcephaly, and many pregnant women are panicked about the potential risk.
Zika was previously a little-known virus that had only been reported as causing mild, flu-like symptoms. It was first reported in Brazil in May of last year, but it wasn't until the fall that alarm bells starting going off as doctors noticed an unusual increase in the number of babies born with microcephaly, and started to suspect Zika might be associated. Despite the uncertainty, scientists and doctors are urging women in affected areas to avoid getting pregnant, or if they're already expecting, to avoid getting Zika.
For thousands of women in Colombia, though, that advice comes too late. The country's health officials say there have been over 30,000 reported cases of Zika infection, including 5,000 expectant mothers.
Because the virus didn't arrive in the country until October of last year, it's still too early to tell if it will have significant impact on microcephaly rates—microcephaly can only be diagnosed in the third trimester and so far the country has had no reports of Zika-related microcephaly. If microcephaly does spike, it will lend further evidence to the hypothesis that Zika comes with birth risks.
"If Zika is proven to be the cause—and the evidence keeps growing—then we should expect to see cases of microcephaly in Colombia by June," said Dr. Marcos Espinal, the director of communicable diseases and health at the Pan American Health Organization, during a teleconference Thursday.
However, proving that Zika is causing microcephaly isn't easy. For one, Zika only causes symptoms in about one in every four infected individuals, and even those with symptoms often don't realize they have it, Espinal said. This is because the symptoms resemble other kinds of illnesses, and are usually mild. The virus only stays in the system for about a week, and the window for testing is only about five days, Espinal explained. Because of this, Zika can go unreported. It's also hard to know what other factors might contribute to microcephaly without being able to track a pregnancy from the start and compare to healthy births. That's why following this specific cohort in Colombia is so crucial.
By collecting data on these women, and comparing them to non-Zika-related births, researchers should be able to establish not only whether or not there's a link between microcephaly and Zika, but also how high the risk is.
"The second country in line is Colombia because we were the second country after Brazil [to report cases of Zika]," Espinal said. "The studies will be telling at that time, but certainly it would be strong evidence that this is really due to Zika."
Zika is now being reported in 28 countries across Latin America. "There are more cases [of Zika] to come," Espinal said. "We have not seen, yet, the peak."