Colombia declares end of Zika epidemic, as other experts urge caution

The Zika virus epidemic in Colombia — which has seen more infections than any country other than Brazil — is over, health officials there said Monday.

Fernando Ruíz, the country’s vice minister of health, told reporters that the country was entering a “post-epidemic phase,” less than a year after the virus was first identified in the country. New cases will continue to appear and could spike again, officials said, but for now, the outbreak has been controlled.

Officials in Colombia said they were also ending their recommendation that couples delay pregnancies.

During the peak of the epidemic in Colombia, back in early February, more than 6,000 cases were reported in a week. But since then, the number of reported cases each week has been dropping, and according to the most recent weekly survey, fewer than 1,000 cases were reported. With the epidemic declared over, Zika is now considered endemic, meaning some level of the virus is still circulating in the country.

A study published this month suggested that the Zika outbreak, which has been primarily driven by mosquitoes, could run through Latin America and the Caribbean within another 18 months. Scientists believe that people who contract Zika can’t get infected again for years — and possibly for life — so the virus could burn itself out in a certain place within about a year, the modeling study found.

But some experts believe the recent decline in cases in Colombia and other countries could be more of a seasonal drop than the true dying embers of an outbreak.

“We’d all like it to be the peak of the outbreak, that would be wonderful,” said Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy. “At the same time, I see nothing that supports that.”

Osterholm said he thought it would take several years for enough people to gain immunity to the virus to prevent it from sweeping through the same area again.

“That is really premature for them to say that,” Osterholm said of the Colombian health officials.

Matthew Aliota, a scientist at the University of Wisconsin who was part of the team that first detected Zika in Colombia, said the virus could be in an “inter-epidemic period” and that cases could surge again at some point.

“This isn’t totally unexpected with Zika virus,” Aliota said, given that people acquire immunity after an infection.

Aliota said a major question is whether Zika will be able to persist in Latin America by surviving in wild monkeys. If that’s the case, the monkeys could serve as a reservoir for the virus, allowing mosquitoes to become infected after biting them and then spread the virus to people who do not have immunity.

Zika typically only causes mild symptoms, including fever and rash. But when a pregnant woman contracts the virus, it can infect the fetus and cause serious birth defects.

The virus was first identified in Colombia last fall and, since then, almost 100,000 people have been infected, including almost 18,000 pregnant women. (Most experts say the total number of cases is higher because so many people who contract Zika do not get symptoms or do not feel sick enough to visit a doctor, where the case would be reported.)

Colombia has been closely watched because it has had the most Zika infections of any country besides Brazil, considered the epicenter of the outbreak. Brazil has had more than 1,700 cases of suspected Zika-related birth defects at this point, but so far, Colombia has seen just 21.

There are a number of possible explanations for that difference. First, other factors in Brazil could play a role in the high number of cases there; possibilities include genetic causes and the interaction between Zika and another disease found in Brazil.

Secondly, not enough time has passed: Zika arrived in Colombia months after it appeared in Brazil. And given that there is a lag between when a pregnant woman contracts the virus and when she delivers her baby, Zika-affected babies would continue to be born for several months even if the virus stopped circulating entirely. Ruíz said Monday that officials expect the peak of babies born with Zika-related defects to come in August or September.

Another reason: Colombia for some time was only reporting defect cases when a baby was born alive, whereas other countries have been reporting defects even if the pregnancy was terminated or resulted in a miscarriage or stillbirth. (Colombia, unlike some Latin American countries, has allowed women who contract Zika to get legal abortions, although advocates say access remains a problem.)

Ruíz said Monday that Zika did not have as large of an impact as officials expected and that it burned through Colombia faster than chikungunya, a related virus spread by the same mosquitoes. In February, health officials forecasted 400 to 600 cases of Zika-related birth defects.

Zika, like a number of other infections, has also been shown to cause Guillain-Barré syndrome, a typically temporary paralysis that sometimes requires patients to get attached to a breathing machine. Colombia has seen 350 cases of Zika-related GBS, Ruíz said, including some fatal cases.