9 Worst Pandemics in Human History

This outbreak of cholera was the most massive pandemic of the 19th century in terms of mortality rate. The disease originated in India and spread to Asia, Europe and the Russian Empire. In tsarist Russia, there were more victims than in other countries: 1,772,439 people fell ill and 690,160 died. The main cause of the disease was the neglect of sanitary practices, in particular the use of contaminated water: toilets could be located near springs and therefore people could bathe in faeces-contaminated rivers. It was only in 1854 that the English physician John Snow noticed a pattern between infection and the water used by those infected. On one of London streets 500 people died in ten days. All of them drank water from the same spring into which, as it turned out, sewage water leaked from the cesspool of a house where a child had recently been ill with cholera.

Most researchers believe that the disease originated in China. Thanks to the advanced transportation system, the Asian flu quickly spread to other countries: more than 70 thousand people died in the United States alone. In total, two to four million people died from the new disease, according to various estimates. The Asian flu was caused by a new virus A subtype (H2N2). This flu pandemic was one of the three that occurred in the 20th century, and it turned out to be the least deadly, as scientists quickly managed to develop a vaccine. The public was long suspicious of the virus, and only after a detailed article by The Times people began to take action. The symptoms were typical for a flu: fever, muscle pain, cough. Fatal cases were associated with development of pneumonia.

This infection is transmitted from a sick person to a healthy one by an ordinary body louse. So the war that came with unsanitary conditions, crowds of people living together and the lack of quality medical care became the beginning of the epidemic. Patients with typhus complain of back pain, high fever and chills, and a few days later a pink rash appears on the body. On the Western Front, lice treatment stations were installed everywhere. Such measures were not taken on the Eastern Front and several million Russian, Polish, and Romanian soldiers died of typhus. The infection continued to haunt the Russians during the Civil war. Typhus killed about three million people. That’s more than the number of war casualties from all the military confrontations between the “Whites” and the “Reds”.

The Spaniards, who first arrived in Mexico in the 16th century, brought not only progress, but also deadly diseases. The worst was cocoliztli (“plague” in Nahuatl). The Spaniards easily tolerated the disease as, according to scientists, they managed to develop immunity. But the mortality rate among the Aztecs was 90%. In 1545-1548, 12-15 million people died from cocoliztli, and another 2 million in 1576-1578. The ancient Aztec civilization was virtually destroyed. The symptoms of the disease included fever, headache, darkened tongue, convulsions, nose and ear bleeding. Scientists still have not identified the real cause of the disease: some researchers consider it a kind of haemorrhagic fever, others see the cause in the Salmonella bacterium which was found in the remains of the dead.

The plague became the first pandemic in human history. The Plague of Justinian which originated most likely in Egypt followed the trade routes to Constantinople, then to Africa, Europe and Asia. Only in 2013, scientists came to the conclusion that the causative agent of the disease was Yersinia pestis, the same bacterium responsible for the Black Death. Symptoms of the disease were diverse: fever, nausea, light sensitivity, and many others. There was almost no working-age population left in the Byzantine empire, handicraft and trade were suspended, most of the survivors were busy arranging funerals — 66% of Constantinople population died. In the following years, the Plague of Justinian went to Europe where, according to various estimates, it killed 25 to 50 million people.

This time the plague originated in the Chinese province of Yunnan and then spread all over the world. In China and India alone, 12 million people became victims of the disease. However, this time the researchers had the opportunity to study the disease more effectively. By the end of the 19th century, the causative agent and the carrier of the disease were finally identified, and the plague ceased to be one of the most dangerous enemies of the mankind: antibiotic treatment is effective against plague bacteria, and rats can be exterminated. The microorganism that causes the plague was called “Yersinia pestis” in honour of the French doctor who discovered it, Alexander Yersen.

HIV is believed to have originated in non-human primates and was transferred to humans in the 20th century. The spread of the disease began in the 1980s. In 1981 several articles appeared about cases of rare diseases — Pneumocystis pneumonia and Kaposi’s sarcoma — in young homosexual men. These illnesses were previously common in completely different age and social groups. Initially, a false opinion spread in the society that only homosexuals and drug addicts were susceptible to the disease, but later it became obvious that anyone can get infected by sexual contact or contaminated blood; children can get the virus by mother-to-child transmission during breastfeeding. Without treatment, an infected person can live an average of 9-11 years, and modern medications can extend this period to 70-80 years. 

In 18 months, the disease killed 90-100 million people. The specific feature of this virus is that it affects healthy young adults, whereas usually the flu is considered dangerous for children, elderly people and the weak. The virus was named “Spanish” by accident — military censorship of the countries participating in World War I did not allow the press to talk about the pandemic, but neutral Spain did not have such restrictions. The history of the Spanish flu clearly shows the importance of effective state anti-pandemic measures. In 1918, Philadelphia authorities did not postpone the parade held to raise money for warring compatriots, and two days later the city had 635 new cases of the disease. Philadelphia became one of the leading American cities in terms of mortality rate from the Spanish flu.

The second pandemic wiped out 30% to 60% of the European population. In some cities, the death rate reached 90% and there was not enough land to bury all the dead. Among the causes of such a large scale disease are protracted wars, droughts and rodent migration. Whole families died in a few days. Symptoms often included the appearance of black and blue spots on the skin, buboes and carbuncles. Modern doctors recommended sexual abstinence, wine with spices and positive thoughts as preventive measures. The disaster left its mark on the further history of mankind: the positive consequences include the admission of women to medical practice and increased requirements to labour organization and remuneration. The plague also came to Rus' (Old Russia) and almost destroyed Smolensk, Pskov and some other cities.