Smallpox, which has ravaged the world for thousands of years, is the only infectious disease that has been eradicated by humans.

In medieval Europe, people often said that there were two things that were inevitable: one was the sweetness and bitterness of love, and the other was smallpox.

Today marks the 44th anniversary of the eradication of smallpox. Let us learn about that history together.

How terrible was smallpox back then?

Before people learned to prevent smallpox by vaccination, 400,000 people died of smallpox in Europe every year. Even in the nearly 200 years since the smallpox vaccine was invented, hundreds of millions of people around the world still died of smallpox. This disease is very harmful. Some European historical records show that 60% of people who contracted smallpox would lose their lives. But at the same time, such a dangerous smallpox is the first infectious disease in human history to be eradicated. What kind of struggle and achievement is this?

Mummies also "get" smallpox?

Smallpox has a long history. We can find traces of it on mummies from 3,000 years ago. In ancient China, people also spread the saying: "It is not difficult to give birth to a child, but only when you can survive smallpox can you be considered to have grown up." This is because smallpox not only has a high mortality rate, but also leaves deep scars on those who survive. Some people will become blind, some will become deaf and dumb, some will even become paralyzed, and many more will have pits like pockmarks on their faces and bodies.

Traces of smallpox pustules were found on the head of the mummy of Pharaoh Ramses V 3,000 years ago. Source: WHO

At the end of the 19th century, with the communication with the outside world, China began to have detailed records about smallpox. For example, in 1909, a local chronicle in Wuhan wrote: That year, smallpox was very prevalent in Hankou. If children under the age of 10 were infected with smallpox, there was a 90% chance that they would not survive. For example, in 1938, Shanghai was also ravaged by smallpox, and the mortality rate at that time was as high as 32.7%. A British historian, Gilead, once described smallpox like this: "Although the mortality rate of plague or other diseases is high, they occur relatively rarely. But smallpox has always been with people, bringing them long-term fear."

The incurable "death"

Smallpox is an infectious disease caused by the smallpox virus. The virus is highly contagious and can survive in the outside world for months even after the patient dies. The smallpox virus is different from other viruses because it is particularly stable in the external environment and can remain infectious for a long time. The most common way of transmission is droplet transmission, but it may also be transmitted through direct contact, aerosols or other routes. When the human body is exposed to the smallpox virus, the virus will multiply rapidly and spread to various parts of the body. The incubation period is usually 7 to 17 days, with an average of about 12 days. Compared with other viruses, smallpox is generally not contagious during the incubation period. But from the beginning of the fever until all the blisters scab and fall off, the patient is contagious.

Smallpox virus. Image source: US CDC

Symptoms of smallpox start with a high fever, fatigue and headache. Later, red spots appear on the body, which gradually develop into fluid-filled blisters. These blisters will scab over and eventually fall off, but may leave permanent scars.

Smallpox symptoms. Image source: US CDC

Although modern medicine has made great progress, we still have no specific medicine to treat smallpox. Throughout history, people have tried various methods to treat smallpox, such as using herbs, cryotherapy, and even wrapping patients in dyed cloth, but these methods have failed to achieve substantial results. In some historical periods, in order to prevent the spread of smallpox, some leaders even ordered the killing of all smallpox patients, but this extreme method still failed to successfully control the spread of the disease.

There is no cure, but there are other ways to overcome it

Although there is no cure for smallpox, people have discovered a strange phenomenon: those who have been infected with smallpox and survived seem to have a "lifelong immunity" to smallpox. They will never be attacked by smallpox again. According to records in ancient Rome, when smallpox was prevalent, the government would even summon those who had survived smallpox, because they were no longer afraid of the threat of smallpox, so they would let them provide nursing services for current patients. This kind of record, in Chinese history, smallpox is called "pox". The book "The Final Discussion of Smallpox" describes a prime minister named Wang Dan in the Song Dynasty. He had many children who died of smallpox, so he was determined to find a way to prevent smallpox. He heard that there was a Taoist priest in Mount Emei who had a "magic method" to prevent smallpox, so he immediately sent someone to invite him. The Taoist priest used the powder ground from the dry scabs of smallpox patients and blew it into the child's nose. Sure enough, the child had mild symptoms of smallpox, but after getting through it, he was able to recover. More importantly, these children did not get smallpox again when they came into contact with patients. This method is called "vaccination", which is an early vaccination method. However, this method of "vaccination" was not widely used at the time, and was more of a secret spread among the people. It was not until the 18th century that British doctor Edward Jenner observed that cows could also have a disease similar to smallpox, which could also be transmitted to humans, but the symptoms were much milder than real smallpox, and that dairy women who had been infected with cowpox would never be infected with smallpox again.

Edward Jenner (1749-1823). Image source: the National Library of Medicine

He gradually formed the hypothesis that "vaccination can prevent smallpox". In order to verify his idea, he conducted an experiment and inoculated the cowpox virus into a healthy child. He found that the child also developed immunity to smallpox. This discovery laid the foundation for modern vaccination. With the development of medicine, we began to understand that smallpox is a double-stranded DNA virus. Unlike RNA viruses such as influenza, SARS, and HIV, it has hardly mutated in human history. This stability makes the development and application of smallpox vaccines relatively simple, and also allows humans to have the upper hand in this smallpox war.

The first infectious disease to be eradicated by humans

There is a lot of popular science about infectious diseases such as smallpox and vaccines, which may give us the illusion that "smallpox will be eradicated once the vaccine is released". In fact, the eradication of smallpox is by no means a one-time effort. Even with a powerful weapon like the smallpox vaccine, the world has worked hard for decades to eradicate smallpox. In 1967, the World Health Organization (WHO) launched a grand plan with the goal of completely defeating smallpox. Their main battlefields were Africa, South Asia, and South America, because at that time, smallpox was under control in most parts of the world due to the widespread use of smallpox vaccines, but in those places, smallpox was still rampant.

Timeline of smallpox eradication. Source: U.S. CDC

First, WHO led local experts to carry out large-scale vaccination in the local area to ensure that everyone was protected regardless of region, rich or poor. At the same time, WHO established a global monitoring system. Whenever a case of smallpox appeared, they would quickly intervene, isolate and track it to ensure that the epidemic would not spread. In order to let everyone understand the harm of smallpox, governments and WHO carried out a lot of public publicity to educate the public on how to prevent the disease.

Cooperation between countries also played a key role. Many countries generously donated funds, vaccines and technical support. Scientists also joined the fight, studying smallpox in depth, developing vaccines that were easier to store and transport and more effective, and providing scientific strategies to fight this tenacious enemy.

In my country, experts such as Mr. Qi Changqing successfully developed a smallpox vaccine. Later, Academician Zhao Kai of the Chinese Academy of Engineering further improved the smallpox vaccine, making it safer, more efficient, and easier to transport and store. Scientific and technological workers, vaccine manufacturers, and medical workers across the country also made unremitting efforts. From the early 1950s to the early 1960s, three national vaccinations and two vaccinations were carried out. Combined with other isolation and immunization measures, it took only 11 years after the founding of New China to eradicate smallpox in China.

And on a global scale, after a fierce struggle, on May 8, 1980, the 33rd World Health Assembly officially announced: "The people of the world have won the victory and eradicated smallpox." In this war with nature, with wisdom and unity, mankind has won a slight victory.

The threat is never far away, and the battlefield is on fire again

Since 2022, monkeypox, a new disease, has come into people's attention and gradually become an epidemic sweeping the world. Monkeypox disease is caused by monkeypox virus (usually abbreviated as MPXV), which is an enveloped double-stranded DNA virus of the genus Orthopoxvirus in the family Poxviridae. The so-called Orthopoxvirus genus also includes the familiar smallpox and cowpox.

Obviously, monkeypox has become a shadow over human health in a new form. Although smallpox has been declared eradicated, similar threats and warnings have never really gone away. The emergence of these new infectious diseases is not only a challenge to our daily lives, but also a test of our awareness of epidemic prevention and solidarity and cooperation.

The fight against smallpox shows that when faced with these unpredictable infectious disease threats, there is no hope without the help of science, and victory cannot be achieved alone. We should always remember that the global human race is a community with a shared future. Only by working together and in unity can we effectively respond to and defeat the threats of these diseases. Because science plus unity is our most powerful weapon to defeat the threats.

References

[1] Zhu Shisheng, “Old Stories of Smallpox”

[2]WHO: Commemorating smallpox eradication – a legacy of hope for COVID-19 and other diseases: https://www.who.int/en/news/item/08-05-2020-commemorating-smallpox-eradication-a-legacy-of-hope-for-covid-19-and-other-diseases

[3] Zhu Chungu. Conclusions on Smallpox[M]. Shanghai Ancient Books Publishing House, 2002.

[4]RiedelS.EdwardJennerandthehistoryofsmallpoxandvaccination.Proc(BaylUnivMedCent).2005Jan;18(1):21-5.doi:

[5]CDC:HistoryofSmallpox:https://www.cdc.gov/smallpox/history/history.html

[6]CDC:Smallpox/MonkeypoxVIShttps://www.cdc.gov/vaccines/hcp/vis/vis-statements/smallpox-monkeypox.html

[7]WorldHealthOrganization: Smallpoxeradication:https://www.cdc.gov/smallpox/pdfs/smallpox-eradication-map.pdf

[6]CaoX.ImmunologyinChina:thepast,presentandfuture[J].NatureImmunology,2008,9(4): 339-342.

Author: Chen Mo'ao, a popular science author

Reviewer: Tang Qin, Director and Researcher of the Medical Science Department of the Chinese Medical Association