Medical advances in the past 100 years mean that many of these diseases no longer pose a risk to the vast majority of people living today. But new threats keep emerging…
Bubonic Plague: 1339-51, Europe and Asia
They called it the Black Death. It was terrifying. Painful, egg-sized swellings on the body signalled the victim had only a week to live. Just being near a sick person was enough to infect you. Churchyards were used as mass graves: the plague bacterium, carried by fleas, killed an estimated 25 million people in China and India before reaching Europe in 1347. Four years later, another 25 million were dead – according to some estimates, half the population of Europe.
Dancing Mania: 1373-1374, Europe.
It was happening in Germany, England and the Netherlands. People hopped, they whirled, they jumped day and night until their feet were bloody and they collapsed from total exhaustion. They could not perceive the colour red; they had a strange aversion to the colour black. Scientists still aren’t sure whether this mysterious illness was a physical or mental phenomenon. Theories range from the rare bacterial illness Sydenham Chorea to ergot poisoning, epilepsy, stress, mass hysteria or even planned religious rituals. Outbreaks occurred from the 7th century until about 1650, then as mysteriously as it had started, the “disease” vanished. The folk tale about the Pied Piper may depict an outbreak of dancing mania.
Measles: 1531-34, Caribbean, Central and South America.
Just a decade after European-brought smallpox first ravaged the New World, another Old World disease cut down millions. In Cuba, two-thirds of the population died; in Honduras, it was 50 per cent. The viral disease is easily transmitted and mainly weakens the immune system, leaving survivors susceptible to pneumonia and infections. Until a vaccine was developed in 1963, measles epidemics occurred every two or three years worldwide. Although today about 85 per cent of children get vaccinated, outbreaks still occur, especially in Africa and Asia.
Smallpox: 1775-1782, North and Central America
When Captain Vancouver explored British Columbia in 1792, he was baffled by the large number of deserted villages. Later historians reconstructed the terrible cause: a smallpox pandemic that began with soldiers in Boston in 1775 and spread along trade routes over the next seven years – north to Montreal, south to Texas and Mexico, and back up the Great Plains to northern and western Canada. North America would never be the same. Viral smallpox was one of the most feared diseases for most of human history. Epidemics afflicted ancient Egypt, China, India and Rome. Early in the 16th-century, it killed upwards of one third of the inhabitants of Central and South America. Paradoxically, smallpox is also a rare pandemic success story. Thanks to global immunization drives, the World Health Organization was able to declare the virus extinct in 1979.
Tuberculosis: 1800-1922, Europe and North America
When Victor Hugo wrote about his heroine Fantine’s death from tuberculosis, he was writing about the most lethal disease of the 19th century. Incredible as it seems, by the end of the century about 80 per cent of city dwellers were infected with TB and 80 per cent of those who developed the full-blown disease died. Even more horrifying is the long shadow this under-the-radar disease casts today. An estimated one third of the global population are carriers of the TB bacterium, and each year nine million fall sick and one million die – many also AIDS victims. A vaccine has been available since 1922; TB can also be cured with antimicrobial drugs.
Cholera: 1817-23, Asia, Middle East and Africa
The cholera bacterium lurks in contaminated water and infects the small intestine, causing severe diarrhea. About 40 per cent of victims die within hours, of dehydration. Although today oral rehydration salts can save lives, it was not so in the past. In 1816, the infection spread beyond India for the first time, carried by British soldiers east as far as Japan and west as far as Syria and Tanzania, killing hundreds of thousands. But that was only the beginning. Six more cholera pandemics swept the globe over the next 150 years, killing millions. Nearly three million cases still occur each year.
Influenza: 1918-19, worldwide
“Spanish flu is the single most devastating disease outbreak in human history,” says Kirsty Duncan, an MP who is also a health studies professor on leave from U of T. It’s the deadliest flu known in the historical record – it killed an estimated 50 million people around the world in the year after the First World War, especially striking down the young and healthy. Flu viruses are so common we have a new pandemic (fortunately, the level of virulence varies) about once a generation. Other recent flu pandemics include the 1968-70 “Asian Flu” that killed as many as four million and the 1889-90 “Asiatic Flu” that felled one million.
Polio: 1952, worldwide.
Although this infectious enterovirus, spread by touch, predates antiquity, it was in the early years of the 20th century that it began to be seen on a pandemic scale. There was – and still is – no cure. The early 1950s peak in particularly virulent cases in the U.S. (nearly 60,000 with one-third resulting in paralysis) was part of the impetus to create a vaccine, developed in 1955 by a team that included University of Toronto researchers. Today, immunization campaigns have almost succeeded in eradicating the disease, although pockets of the virus linger in Nigeria and Central Asia.
HIV/AIDS: 1970s-present, worldwide
Transmitted through bodily fluids, the HIV virus originated in central Africa. For years, the disease spread slowly; the virus wasn’t even identified until the early 1980s after an epidemic began among gay men in western countries. HIV-AIDS destroys the immune system, putting people at risk of death from other diseases such as cancer or pneumonia, or from infections. There is no cure, although anti-retroviral drugs prevent the virus from spreading and killing more immune cells. HIV-AIDS has killed more than half a million North Americans, but in Southern Africa, an estimated 25 million have lost their lives, with 35 million more still infected – including many children born with the virus.
By bringing artificial intelligence into chemistry, Prof. Aspuru-Guzik aims to vastly shrink the time it takes to develop new drugs – and almost everything else