Smallpox was so deadly that Koreans called it, ‘Hohwan Mama (Evil goddess that spreads a disease as horrible as the death from a tiger's bite).’ It killed three out of ten infected people, and 400,000 people used to die from smallpox each year as late as the 18th century.

The plague is spread through parasitic fleas on mice. The reason the plague, which swept across Europe, is particularly terrifying is that it spreads quickly and leads to death in a very short time. The population of Europe before the plague was estimated at 450 million, and 75 to 200 million died due to the disease. Ironically, the Latin phrase, ‘carpe diem,’ was coined during this time.

The Spanish flu was the worse epidemic of the 20th century. It broke out in America during World War I and spread worldwide. At the time, approximately 600 million people out of 1.6 billion people around the world were infected. 25 million people died from the Spanish flu, which is far more than the 9,381,551 people that died during the First World War. It triggered worldwide influenza vaccinations.

It is estimated that the disease killed 70,000 people in America and approximately two million people around the world. It broke out in southern China and spread to the world through Hong Kong. Some influenza vaccines were used for the first time, and the use of antibiotics as treatment for pneumonia began.

It started in Hong Kong and spread to Vietnam, then to America after US soldiers who fought in the Vietnam War returned home, and then to the rest of the world. It is estimated that approximately one million died from the Hong Kong Flu. Later, a full-scale vaccination began.

It broke out independently by the Ebola River in the Democratic Republic of Congo. It manifested 50-90% mortality rate within a week after infection and it causes problems in all organs through the blood vessels that lead to bleeding and eventually death. The cause of the disease was not known at the time, but recent studies strongly indicate fruit bats as the probable cause.

It was first reported from the cases of homosexual and drug addicted patients. The virus was also detected from the blood sample of a Congolese man in 1959 in a reverse trace. Those infected suffer from various diseases due to immune deficiency after a long latency period of 6-12 years and eventually die. Korea is the only country in the world that provides free treatment for AIDS.

SARS first broke out in a traditional marketplace in Guangdong, China. The fact that a bat was the vector of infection is also similar to COVID-19. The infected person showed severe flu and pneumonia symptoms. 8,273 people were infected in 38 countries around the world, and 775 of them died.

It is called ‘swine flu’ because it emerged at a pig farm in Mexico. The risk increased as avian, swine, human influenza viruses were complexly mixed. Although the mortality rate was low while the infection rate was high, 14,286 people died as of January 18, 2010.

MERS is an acute respiratory infection that was first reported in a patient with severe pneumonia in Saudi Arabia. 1,475 people were infected and 515 people died as of September 1, 2015. Korea suffered directly from MERS at the time and had over 100 infected people in less than a month after the first confirmed case in May 2015, incurring domestic and international criticism that its quarantine policies had failed. The cause of failure resulted from the delayed disclosure of information such as the name of the hospital that an infected person visited.

The first pneumonia patient who also suffered from high fever and a severe cough was found in Wuhan, China. It quickly spread throughout the world, infecting tens of thousands of people. Some of its characteristics are that it is spread through the respiratory tract and is highly contagious in the early stage of infection when there are not many symptoms. The World Health Organization declared it as a pandemic in March 2020. The cumulative number of confirmed cases around the world rose to 10,074,630, and the number of cumulative deaths exceeds 500,000 as of June 28, 2020.