In 1958, a lab in Denmark noticed a strange smallpox-like disease in monkeys that had arrived from Malaysia. Tests were done at the State Serum Institute in Copenhagen, and scientists realised they had discovered a brand-new virus.
Because the virus and the disease occurred in monkeys, they named it monkeypox.
Tracing link to Africa
Between 1958 and 1968, several outbreaks of monkeypox occurred in lab monkeys, and because all the monkeys had come from Asia, scientists at first thought the virus reservoir was in Asia.
To test this theory, they took blood samples from more than a thousand monkeys in India, Indonesia, Malaysia and Japan, but found that none of the animals had monkeypox antibodies. This was odd because a viral infection produces antibodies that can be found in an animal’s blood even years later.
The mystery of the monkeypox virus’s natural reservoir was solved in the 1970s after the first case of monkeypox in a human was confirmed in Zaire – now known as the Democratic Republic of the Congo – in central Africa.
This time scientists collected blood samples from animals in central and western Africa, and sure enough 7 species of monkeys and 2 species of squirrels had monkeypox antibodies.
While the mystery of monkeypox’s origin had been solved, one question remained – how had Asian monkeys become infected with it?
The answer was that, along with the Asian monkeys, the European and American labs had also imported some monkeys from west Africa, scientists Frank Fenner, Riccardo Wittek and Keith Dumbell wrote in their 1989 book, ‘The Orthopoxviruses’.
The Asian and African monkeys had either come in contact with each other or the virus had been transferred through their human handlers. After strict handling rules were enforced in 1968, monkeypox outbreaks in labs stopped.
But the discovery of human monkeypox set alarm bells ringing for other reasons.
Threat to smallpox fight
A global campaign to wipe out smallpox had started in 1967. It was so successful that by 1972, Americans didn’t need smallpox vaccinations. And on the 8th of May, 1980, the World Health Organization declared the whole world was smallpox-free. It’s the only disease we have been able to eradicate so far.
However, in 1970 scientists feared that if the monkeypox virus – which was similar to smallpox and produced almost identical symptoms – infected humans, it would jeopardise the ‘Intensified Smallpox Eradication Program’.
WHO asked the labs affected by monkeypox in America and Europe if they had recorded cases of animal-to-human transmission, but none of them had. And yet, a 9-month-old village boy who was admitted to the Basankusu Hospital in Zaire on the 1st of September, 1970 had tested positive for monkeypox.
His village had been vaccinated for smallpox, and nobody else in the area had reported fever with a rash, so smallpox was ruled out. But the boy himself was not vaccinated. He was the only unvaccinated member of his family. He got fever on the 22nd of August and developed a rash on the 24th.
While he was at the Basankusu Hospital, his pox scabs were collected and sent to Moscow, where tests showed he had monkeypox. He made a slow recovery over the next two months, but just when doctors were thinking of discharging him, he caught measles in the hospital on the 23rd of October and died 6 days later.
A poor spreader
Now that it was clear that monkeypox could infect humans, scientists became more vigilant. In 1971, suspected cases of smallpox in Liberia, Nigeria, Sierra Leone and Ivory Coast turned out to be monkeypox infections.
But the good news was that monkeypox didn’t affect humans outside its natural reservoir in central and western Africa. Of the 404 cases reported between 1970 and 1986, about 90% occurred in small villages inside tropical rain forests where people led a hunter-gatherer life and had frequent contact with wild animals.
In one case a chimpanzee abducted a 6-month-old child from a Zaire village. People chased and rescued the child but a week later it came down with fever and a rash that turned out to be monkeypox. Zaire had the maximum cases of monkeypox – 386 out of the 404
Data also showed that monkeypox was not very contagious among humans. With smallpox, 58% of the contacts of a patient used to get infected, but with monkeypox this percentage was just 9% among people who had not taken the smallpox vaccine
In case you are wondering, the smallpox vaccine does provide a high degree of protection against monkeypox because the two viruses are so similar. And in the 1980s data from Africa showed that most of the severe monkeypox infections and deaths occurred in unvaccinated children.
Another interesting and reassuring finding was that monkeypox outbreaks naturally died out after a maximum of 11 steps of human-to-human transmission. That explains why even after lurking in the rain forests of Africa for centuries monkeypox could not become a common human disease even when the smallpox vaccine wasn’t around
But if monkeypox was always a disease of central and western Africa, how has it spread in Europe now?
Clues from America
We don’t know for sure, but the 2003 monkeypox outbreak in America might provide clues. That year, 82 infections were recorded in the US during May and June. New York Times journalist Denise Grady has described the chain of events in her book ‘Deadly Invaders’.
She says the first US cases appeared in the state of Wisconsin. A family got infected from its pet prairie dog, which is not really a dog but a squirrel. The family recovered but the sick pet didn’t.
In another case, an 11-year-old boy got monkeypox after his friend’s prairie dogs bit him. Later, it was found that every single US case had started from contact with a prairie dog. One particular animal managed to infect 18 people. A 10-year-old girl who owned 3 prairie dogs in Illinois became so sick she had to be given morphine to suppress her pain. She had sores inside her throat, Grady writes.
So how did prairie dogs, which are an American species, become carriers of monkeypox? Grady says owning prairie dogs was a fad in 2003, with people paying up to 150 dollars for one.
A Chicago pet store called Phil’s Pocket Pets sold them in large numbers, but it also had a giant Gambian pouched rat imported from Ghana in west Africa. The prairie dogs probably got infected from the African rat.
And Phil’s was just one shop. Altogether 800 animals had been sent from Ghana in one shipment in April 2003. All the imported animals had to be traced and put down. Prairie dogs exposed to the imported animals also had to be killed.
Had the disease spread among America’s wild animals it would have become impossible to eradicate. Luckily, the outbreak ended without any human death, but the US banned the import of African rodents after it, and also the sale of prairie dogs as pets.
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