A pandemic (from Greek, pan, "all" and demos, "people") is an epidemic of an infectious disease that has spread across a large region, for instance multiple continents or worldwide, affecting a substantial number of people. A pandemic is an epidemic occurring on a scale that crosses international boundaries, usually affecting people on a worldwide scale. A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance, cancer or other chronic diseases such as diabetes or hypertension are responsible for many deaths, but they are not considered a pandemic because the disease is neither infectious nor contagious.

How about the solutions to the pandemic? While protective measures at the individual level are crucial, real solutions come with collective action. Pandemics affect “all people,” so should the solutions be. “Every sheep is hung by its own leg,” says the Turks, meaning that everyone pays for their own mistakes, not for the mistakes of others. In the case of pandemics, mistakes are paid for by all. Nevertheless, when the threat is big and resources are limited, individuals, as well as nations, may choose to act on their own instead of globally.

There is a tale which gives many lessons to us based upon this proverb. Bahlul Dana was a well-known judge and scholar who lived at the time of the mighty Caliph Harun al-Rashid. Bahlul advised people to avoid doing wrong things and invited everyone to be kind and wise. Some people did not like his warnings and they went to Harun al-Rashid. They complained about Behlul Dana and said that “My sultan, tell him to leave us alone and not to warn about everything. Each sheep is hung by its own leg.” Upon these complaints, Harun al-Rashid summoned him to his court and warned him not to disturb people with his warnings. Bahlul Dana left the palace without saying anything. He slaughtered a few sheep and hung them from their legs on a corner of the street and told people not to touch them. As days passed, the hanging carcasses started smelling very bad. When the smell became unbearable, the same people went to Harun al-Rashid again. “We cannot stop the smell of the sheep Bahlul hung. It bothers us very much. Tell him to dispose of them!”

Harun al-Rashid wondered why Bahlul did such a thing. “Bahlul, why did you do such a strange thing? He answered: “I did not do anything. I just hung each sheep by its own leg. But it seems that even if each sheep is hung by its own leg, it still disturbs the whole environment and harms everyone. A villain does not hurt only himself; he harms everyone."

The story gives an important lesson: Sometimes the consequences of our ignorance and selfish behaviors may harm other people first, and we may choose to ignore them; however, as selfish as it is, we rarely can do away with selfish behaviors, not least when the consequences are global as in a pandemic. When we look at the pandemics throughout the history, we can see the same perspective. During human history, there have been a number of pandemics which have affected millions of people and which probably could have been curbed if people could have acted collectively.

Pandemics in history

Antonine Plague (165 AD): The Antonine Plague (Plague of Galen) was an ancient pandemic that affected Asia Minor, Egypt, Greece, and Italy, and is thought to have been either Smallpox or Measles. This unknown disease, which was brought to Rome by soldiers returning from Mesopotamia around 165 AD, was the cause of high death toll: 5 million people dead and the Roman army was literally decimated.

Justinian Plague (541-542): The Plague of Justinian was an outbreak of the bubonic plague that affected the Byzantine Empire and Mediterranean port cities. It was carried over the Mediterranean Sea from Egypt. The plague decimated Constantinople and spread like wildfire across Europe, Asia, North Africa and Arabia, killing an estimated 25 to 100 million people, perhaps half of the world’s population. It was spread was by infected fleas and perhaps body lice. Its mortality rate was around 10% with treatment, up to 90% without.

The Black Death (1346-1353): Another outbreak of Plague was seen in Europe, Africa, and Asia, with an estimated death toll between 75 and 200 million people between 1346-1353. In the 14th century the world’s population was estimated to be 443 million. That means the Black Death killed between 17-45% of the entire global population. This plague is estimated to have resulted from the increased rat populations and fleas.

Ports were major urban centers at the time and they were the perfect breeding ground for these rats and fleas. To stop the spreading of the disease in the Venetian-controlled port city of Ragusa, they decided to keep newly arrived sailors in isolation until they could prove that they weren’t sick.

At first, sailors were held on their ships for 30 days, which became known in Venetian law as a trentino. The Venetians increased the forced isolation to 40 days or a quarantino, which is the origin of the word “quarantine” after which its practice started in the Western world.

Third Cholera Pandemic (1852–1860): There have been seven cholera pandemics in history and the third cholera pandemic has been considered the deadliest one. It lasted from 1852 to 1860 and it originated from India, spreading from the Ganges River Delta to Asia, Europe, North America and Africa. Around one million people died during this pandemic.

Flu Pandemic (1889-1890): The “Asiatic Flu” or “Russian Flu” was thought to be an outbreak of the Influenza A virus subtype H2N2 or Influenza A virus subtype H3N8, which are subtypes of influenza A viruses. These viruses are divided into subtypes on the basis of two proteins; hemagglutinin (HA) and neuraminidase (NA), which are present on the surface of the virus. There are 18 known HA subtypes and 11 known NA subtypes. Many different combinations of HA and NA proteins are possible and different subtypes of influenza viruses caused many pandemics during history.

The first cases of this pandemic were observed in 1889 in three separate and distant locations: Bukhara in Central Asia (Turkestan), Athabasca in northwestern Canada, and Greenland. Rapid population growth of the 19th century in urban areas helped the spread of the flu, resulting a death toll of about one million people.

Sixth Cholera Pandemic (1910-1911): It originated in India and killed over 800,000 people. It had spread to the Middle East, North Africa, Eastern Europe and Russia. It was the last American outbreak of cholera between 1910–1911. American health authorities quickly took precautions and isolated the infected. By the end of the pandemic, only 11 deaths occurred in the US, which showed the importance of precautions and preparedness.

Spanish Flu (1918): Between the spring of 1918 and the summer of 1920, a deadly outbreak of influenza tore across the globe, infecting over a third of the world’s population (500 million) and ending the lives of 30-50 million people. The mortality rate was estimated at 10% to 20%, with up to 25 million deaths in the first 25 weeks alone. It was caused by the H1N1 influenza A virus and transmitted by airborne transmission from coughing, sneezing, and breathing. Although previous flu pandemics killed juveniles, the elderly or already weakened patients, Spanish flu affected completely healthy young adults. Modern advancements in transportation and troop movements during World War One helped its spread. The true origin of the virus could be France, England, China, and the United States and it is estimated that the virus originated in birds, and either jumped to humans directly or used pigs as an intermediary before jumping to humans.

Asian Flu (1956-1958): It originated in China in 1956 and lasted until 1958. In these two years, the Asian Flu traveled from the Chinese province of Guizhou to Singapore, Hong Kong, and the United States. It was a pandemic of Influenza A of the H2N2 subtype and World Health Organization believe it caused approximately 2 million deaths, around seventy thousand in United States alone.

Hong Kong Flu (1968): The flu pandemic in 1968 was caused by the H3N2 strain of the Influenza. The first case was reported on July 13th, 1968 in Hong Kong, and it took only 17 days before outbreaks of the virus were reported in Singapore and Vietnam. Only after three months it was seen in the Philippines, India, Australia, Europe, and the United States. Although it had a low mortality rate (0.5%), it still resulted in the deaths of more than a million people, including 500,000 residents of Hong Kong, approximately 15% of its population at the time.

Recent pandemics

Swine flu (2009-2010): It was an infection caused by one of several types of swine influenza viruses. This virus is any strain of the influenza family of viruses that is endemic in pigs. Transmission of the virus from pigs to humans is not common and does not always lead to human flu, often resulting only in the production of antibodies in the blood. If transmission does cause human flu, it is called zoonotic swine flu. People with regular exposure to pigs are at increased risk of getting infected by swine flu.

It is estimated that in the 2009 flu pandemic, there were 18,449 confirmed fatalities from swine flu. However, in a 2012 study, the Center for Disease Control (CDC) estimated more than 284,000 possible fatalities worldwide, with a range from 150,000 to 575,000 deaths. In August 2010, the World Health Organization declared the swine flu pandemic officially over.

Severe Acute Respiratory Syndrome (SARS): It is a viral respiratory disease caused by a SARS-associated coronavirus. SARS was first reported in Asia in February 2003. The illness spread to more than two dozen countries in North America, South America, Europe, and Asia before it was contained the same year.

SARS is an airborne virus and can spread through small droplets of saliva in a similar way to the cold and influenza. It was the first severe and readily transmissible new disease to emerge in the 21st century and showed a clear capacity to spread along the routes of international air travel. SARS can also be spread indirectly via surfaces that have been touched by someone who is infected with the virus.

Most patients identified with SARS were previously healthy adults aged 25–70 years. A few suspected cases of SARS have been reported among children under 15 years. The case fatality among persons with illness for probable and suspected cases of SARS is around 3% and 770 people died from SARS. No cases of SARS-CoV have been reported worldwide since 2004. As of 2020, SARS is considered eradicated in humans, but considering that the virus also infects animals it is possible that it will re-emerge in the future.

Ebola Virus Disease (EVD): EVD is a rare and deadly disease seen in humans and animals like bats, monkeys, gorillas, and chimpanzees. It is caused by viruses located mainly in sub-Saharan Africa. People can get EVD through direct contact with an infected animal or a sick or dead person infected with Ebola virus.

The disease was first identified in 1976, in two simultaneous outbreaks: one in South Sudan and the other Democratic Republic of the Congo. EVD outbreaks occur intermittently in tropical regions of sub-Saharan Africa. From 1976 to 2012, the World Health Organization reports 24 outbreaks involving 2,387 cases with 1,590 deaths. The largest outbreak to date took place in West Africa from December 2013 to January 2016, with 28,646 cases and 11,323 deaths. It was declared no longer an emergency on 29 March 2016.

Middle East Respiratory Syndrome (MERS): It is an illness caused by a virus (more specifically, a coronavirus) called Middle East Respiratory Syndrome Coronavirus (MERS-CoV). It is a virus transferred to humans from infected dromedary camels (zoonotic virus). It is contactable through direct or indirect contact with infected animals. MERS-CoV has been identified in dromedaries in several countries in the Middle East, Africa, and South Asia. Health officials first reported the disease in Saudi Arabia in September 2012. A total of 27 countries have reported cases since 2012, leading to 858 known deaths due to the infection and related complications. About 3 or 4 out of every 10 patients reported with MERS have died.

Zika: Zika virus is a mosquito-borne flavivirus that was first identified in Uganda in 1947 in monkeys. It was later identified in humans in 1952 in Uganda and Tanzania. From 2007 to 2016, the virus spread eastward, across the Pacific Ocean to the Americas, leading to the 2015–2016 Zika virus epidemic. In 2015, and strongly intensified throughout the start of 2016, with more than 1.5 million cases across more than a dozen countries in the Americas. The World Health Organization warned that Zika had the potential to become an explosive global pandemic if the outbreak was not controlled. Zika is spread mostly by the bite of an infected mosquito. Zika can be passed from a pregnant woman to her fetus, and an infection during pregnancy can cause certain birth defects. There is no vaccine or medicine for Zika yet but there are several clinical trials going on.

Ongoing pandemics

Although we are primarily focused on the COVID-19 pandemic nowadays, there is another major pandemic that has been going on for many years.

HIV/AIDS: HIV originated in Africa and spread to the United States via Haiti between 1966 and 1972. AIDS is currently a pandemic in Africa, with infection rates as high as 25% in southern and eastern Africa. In 2006, the HIV prevalence among pregnant women in South Africa was 29%. Currently there are between 31 and 35 million people living with HIV, the vast majority of those are in Sub-Saharan Africa, where 5% of the population is infected (21 million people).

Since its clinical discovery in 1981, approximately 32 million people died from HIV/AIDS – around 865,000 people on average each year – ranking it as the fourth-leading cause of death. Although extensive research on HIV has been conducted there is unfortunately no vaccine yet.

COVID-19: Coronaviruses have been known to exist for many years, but a new strain of coronavirus was first identified in the city of Wuhan, China, in December 2019. It has caused a cluster of cases of an acute respiratory disease, which is referred to as coronavirus disease 2019 (COVID-19). It was characterized as a pandemic by the World Health Organization on March 11^th, 2020. As of February 26, 2021, more than 113 million people were infected and nearly 2,5 million people lost their lives.

When COVID-19 first started, it spread rapidly worldwide within months between people because no one on earth had any immunity to Covid-19. It was a novel virus that took the entire world by storm. Now after a full year, and after a number of vaccines have been introduced by the end of 2020, many nations still impose measures like social distancing and stay-at-home orders as schools and businesses are mostly closed.

Although several vaccines are in the market and have started to be administered, it is still hard to predict the consequences of this pandemic at the time of writing this article. But we can learn from pandemics in history to determine our best courses. The main goal is to achieve herd immunity, which means that enough people in a community are protected from getting a disease because they have already had the disease or they have been vaccinated. Herd immunity makes it difficult for the virus to spread from person to person, and it even protects those who cannot be vaccinated, like newborns. The percentage of people who need to have protection in order to achieve herd immunity varies from disease to disease, and at this point we still don’t know this percentage for COVID-19 – this means we may have long way to go.

Every shortcoming or failure to comply with measures only brings more harm towards our collective health. We have to keep in mind that we are living in a global world that is akin to a village now. National crisis plans are not enough, and international collaborative plans should be available for the management of any pandemic. Nations need to collaborate by taking precautions jointly, and countries who are under the heavy effects of the pandemic should be supported. A fair distribution of vaccines or other possible treatment options is necessary. We can overcome this type global threats if we can act collectively with all nations.

• WHO Statement Regarding Cluster of Pneumonia Cases in Wuhan, China". WHO. 31 December 2019. Retrieved 12 March 2020.
• Stawicki, Stanislawp; et al. (2020). "The 2019–2020 novel coronavirus (Severe acute respiratory syndrome coronavirus 2) pandemic: A joint american college of academic international medicine-world academic council of emergency medicine multidisciplinary COVID-19 working group consensus paper". Journal of Global Infectious Diseases. 12 (2): 47–93. doi:4103/jgid.jgid_86_20
• https://www.worldometers.info/coronavirus/
• https://en.wikipedia.org/wiki/Pandemic
• https://www.visualcapitalist.com/history-of-pandemics-deadliest/