HAVANA, Cuba (AP) — Six months after President Raul Castro declared war on the Zika virus in Cuba, a militarized nationwide campaign of intensive mosquito spraying, monitoring and quarantine appears to be working.

Cuba is among the few countries in the Western Hemisphere that have so far prevented significant spread of the disease blamed for birth defects in thousands of children. Only three people have caught Zika in Cuba. Thirty have been diagnosed with cases of the virus they got outside the island, according to Cuban officials.

 Many are now watching to see whether Cuba is able to maintain control of Zika or will drop its guard and see widening infection like so many of its neighbors. The battle against Zika is testing what Cuba calls a signal accomplishment of its single-party socialist revolution — a free health-care system that assigns a family doctor to every neighborhood, with a focus on preventive care and maternal and pediatric health. That system has come under strain in recent years as thousands of specialists emigrate to the U.S., Europe and South America for higher pay and the allied government of Venezuela reduces the flow of subsidized oil that has been keeping Cuba solvent.

U.S. government scientists fly to Havana in November for a two-day meeting on animal-borne viruses such as Zika, the first conference of its kind since the re-establishment of diplomatic relations a year ago. American researchers say they are eager to learn more and help incorporate Cuba into U.S.-backed international health programs after a half-century without significant professional interaction.

“Probably in the last decade we’ve had two people that have gone down there for anything,” said F. Gray Handley, associate director for international research affairs at the U.S. National Institute of Allergy and Infectious Diseases. “It has been pretty much of a black box.”

So far, there have been about 40 cases of Zika caused by mosquito bites in Florida. Health officials don’t expect widespread outbreaks in the mainland U.S. but there are thousands of cases in Puerto Rico and countries such as Brazil and Venezuela are struggling with large-scale infection.

International medical experts familiar with Cuba say other countries can learn from Cuba’s intense focus on preventing disease, which led the government to decimate the mosquito population by spraying virtually every neighborhood in Cuba this spring.

“Cuba’s response has been strong and effective,” said Dr. Cristian Morales, the World Health Organization’s representative in Cuba. “It has to do with the capacity to organize the population. Applying it to other countries, other contexts, would be extremely difficult.”

Other elements of Cuba’s success so far against Zika may simply not apply to other nations because they are inextricably tied to a form of government unique in the Western hemisphere.

Most aspects of life in Cuba are controlled by a single-party state that rigorously monitors citizens’ activities. From neighborhood doctors to reporters to block watch captains, most people in Cuba work for a massive government apparatus whose components all ultimately answer to a single unelected leader, Raul Castro, who heads the military, the state and the Communist Party.

In February, as Zika spread through South America, Castro announced that he would be deploying the army to spray homes and workplaces because of the failings of civilian government fumigators, whom Cubans frequently brushed off to avoid the smelly, noisy filling of their homes with insecticidal fog.

“Our people will be able to demonstrate their ability to organize to maintain the levels of health achieved by the revolution and avoid our families suffering,” he wrote. “As never before in similar efforts, we must be ever-more disciplined and demanding.”

In the following weeks, Cubans cities, towns and villages filled with olive-clad soldiers moving door-to-door with handheld foggers, and using sprayer trucks to blanket entire streets with clouds of insecticide.

Cuba’s approach compares favorably to the effort in Florida, where officials are spraying areas where Zika cases have already started cropping up, said Carlos Espinal, director of the Global Health Consortium at Florida International University in Miami.

“They started very early in advance of the Zika virus,” he said. “Once you start going behind the cases then it’s complicated, you’re just detecting once the transmission is already in place.”

The Cuban state has officials from immigration agents to neighborhood doctors watching for Zika, especially in the thousands of doctors, nurses and support staff who work overseas in programs that earn the Cuban government billions of dollars a year in badly needed hard currency. 

“The neighborhood family doctor is told, ‘In your community there are 10 people who’ve gone to Jamaica. Two are doctors, three are nurses and the other six or five are business people, tourists, whatever.’ And he has to keep an eye on them, go to their homes, call them,” said Professor Jorge Perez, director of the Pedro Kouri Tropical Medicine Institute in Havana.

Perez said 1,700 people with fever or other symptoms had been quarantined for 24-48 hours while being tested for Zika. All pregnant women are tested for Zika in their first trimester, he said. Every worker sent overseas on a government “mission” is quarantined and tested before returning to the island.

“We’re surrounded by Zika, everywhere,” he said. “We’ve learned that it’s better to prevent than to treat.”

The Cuban government holds regular video conferences among top health officials, military officers, Communist Party officials and sanitation and water experts in the capital and in Cuba’s 14 provinces. Even elementary- and middle-school students had been drawn into the campaign, with teams of children as young as 10 sent door-to-door to check for standing water where mosquitoes breed and distribute information about Zika. Those who defy orders to eliminate standing water or trash or allow inspections or fumigation are fined.

“In our neighborhood people watch out for surges of mosquitoes, keep things clean and work with the neighborhood to raise their awareness,” said Gerardo Olvera, 51, a self-employed vendor of phone cards in Havana. “Meanwhile the authorities are visiting, fumigating. It’s all designed to get everyone involved.”