Death in Cuba: Revisiting the theory that CIA biological warfare caused the deadly 1981 Dengue outbreak.


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In 1981, an outbreak of dengue fever swept across Cuba, leading to tens of thousands of cases and hundreds of deaths. In the years that followed, some Cubans began to believe that the outbreak was not a natural occurrence, but rather the result of a secret biological warfare program conducted by the United States government.

This conspiracy theory centers around the alleged involvement of the Central Intelligence Agency (CIA) in the outbreak, and has persisted to this day despite official denials and lack of evidence.

By all counts, it was a severe outbreak and traumatized the entire nation. Maria G. Guzman, a researcher who, as a young scientist, was involved in the national response to the outbreak recalled the scale of the outbreak in an article in Science,

In the 1981 epidemic in Cuba, more than 344,000 cases were reported, of which 10,000 were deemed severe and very severe. There were 158 fatalities. All but 57 of these were children, a chilling factor that only added to the national dread elicited by this epidemic. Once the first cases were detected, I found myself—despite my youth and inexperience—playing a crucial national role in the diagnosis of a severe viral disease that had been relatively unknown in Cuba or the region before. (Although a milder dengue epidemic had been reported in Cuba in 1977-1978, I was not involved in the country's scientific and medical response at that time.)

At the time, Fidel Castro was quick to pounce on the theory that the United States had waged biological warfare on the island nation. According to a New York Times report at the time

On July 26, in the midst of the outbreak of the mosquito-borne disease, Fidel Castro, the Cuban leader, publicly suggested that the United States might have bee n responsible for the introduction of a new strain of dengue fever, known as dengue-2, into Cuba.

In a televised speech celebrating his revolution, Mr. Castro said: "We share the people's convictions and strongly suspect that the plagues that have been punishing our country, especially the hemorrhagic dengue, could have been introduced into Cuba, into our country, by the C.I.A."

Mr. Castro also recounted previously published accounts of efforts by the Central Intelligence Agency to commit sabotage or assassinations in Cuba. He also read reports published through the years on United States research into biological warfare.

"We urge the United States Government to define its policy in this field, to say whether the C.I.A. will or will not be authorized again- or has already been authorized - to organize attacks against leaders of the revolution and to use plagues against our plants, our animals and our people," he said.

On July 27 the State Department said Mr. Castro's charges of possible United States involvement in the epidemic were "totally without foundation."

The origins of the conspiracy theory can be traced back to a number of factors. Firstly, there is a long history of covert US involvement in Cuba, dating back to the early days of the Cold War. This has included attempts to overthrow the government of Fidel Castro and support for anti-Castro groups. Additionally, the US government has a well-documented history of conducting secret biological and chemical warfare experiments, such as the infamous Tuskegee Syphilis Study and the MK-Ultra mind control program.

Against this backdrop, it is perhaps not surprising that some Cubans would be suspicious of US intentions, particularly in the aftermath of the dengue outbreak. However, the conspiracy theory gained particular momentum due to the actions of a few key individuals.

One of these was Dr. Manuel Carballo, a Canadian epidemiologist who was working in Cuba at the time of the outbreak. In 1991, he published an article in the Journal of the American Medical Association in which he suggested that the strain of dengue that had caused the outbreak was unusual and may have been artificially created. He later retracted this claim, stating that he had no evidence to support it, but by then the damage had been done.

Another key figure in the conspiracy theory is a woman named Alina Fernández, who is the daughter of Fidel Castro’s former mistress. In 1993, she published a book called “Castro’s Daughter” in which she claimed that the dengue outbreak was the result of a deliberate US plot to undermine the Cuban government. Fernández, who now lives in the United States and is a vocal critic of the Cuban regime, has continued to promote this theory in interviews and public appearances.

Despite the lack of concrete evidence to support the conspiracy theory, it has gained a significant following in Cuba and beyond. Supporters point to a number of supposed “smoking guns” that they believe prove the CIA’s involvement. One of these is the fact that in 1981, a Cuban defector named Eduardo Arocena was arrested in the United States and charged with terrorist activities. Arocena was the leader of a militant anti-Castro group known as Omega 7, and it is alleged that he had connections to the CIA. Supporters of the conspiracy theory argue that Arocena may have been involved in the dengue plot, although there is no direct evidence to support this.

Another supposed piece of evidence is the fact – really a misconception as many parties have patents on attenuated strains of countless viruses – that the US government has a patent on a strain of dengue fever. Conspiracy theorists argue that this proves that the US was able to create a new, more virulent strain of the disease and release it in Cuba. However, the patent in question is for a specific method of creating a vaccine for dengue, not for the virus itself.

Interestingly, the Dengue outbreak wasn’t the only instance where the Castro government accused the United States of engaging in biological warfare in the country. A decade before in 1971, a viral outbreak had infected most of the country’s pigs and led to a mass culling. A 2020 episode of Gimlet Media’s Science Vs. podcast recounted the events

And all around the country pigs were getting killed by the Government. In total more than 400,000 pigs were killed - more than a quarter of all the pigs in Cuba at the time.  And that made people angry. Many Cubans didn't believe there was a virus at all… some thought Castro just killed the pigs to terrorize and control the people.  

Was that the epidemic that the soldiers were talking about? It was real...  Cuban scientists had detected that a virus was killing pigs … and to stop the spread -- they burned pigs in virus hot spots. And it worked. Cuba controlled the outbreak. But having to kill so many of them was devastating.

And soon people started asking questions. About where this mysterious virus came from -- that got into Cuba and all of a sudden started killing their pigs?  Cuba was pretty isolated at the time… and this virus had never been in the country before --- in fact it had never been anywhere near the region... So how did it get to Cuba in the first place?

An idea took hold. People started saying that the virus was intentionally released into the country… by one of the most powerful Governments in the world. The United States.

As with the origins of the Dengue outbreak in 1981, many Cubans still believe the 1971 incident to be the handiwork of the CIA.

Despite the lack of evidence, the conspiracy theory about the CIA and dengue fever in Cuba continues to persist. It is fueled by a number of factors, including distrust of the US government, the history of covert US involvement in Cuba, and the actions of a few key individuals who have promoted the theory. While it is unlikely that the truth about the outbreak will ever be definitively proven one way or the other, it is important to maintain a healthy skepticism of such conspiracy theories until incontrovertible facts emerge supporting the narrative.

WORDS: Scientific Inquirer Staff.


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