Brief review of other pandemics and epidemics

More than two months after the first case of coronavirus was diagnosed in China in late December, the World Health Organization declared COVID-19 a worldwide pandemic on March 11.

“Pandemic is not a word to use lightly or carelessly,” WHO Director-General Tedros Adhanom Ghebreyesus said. “It is a word that, if misused, can cause unreasonable fear, or unjustified acceptance that the fight is over, leading to unnecessary suffering and death.”

Previous pandemics and epidemics have killed tens of millions of people and caused worldwide havoc for centuries. So yes, the words “pandemic” and epidemic” can be scary. Here’s what you should know about both terms and about pandemics and epidemics throughout history.

What’s the difference between an epidemic and a pandemic?

An epidemic is an outbreak of a disease that is beyond “what is normally expected in that population in that area,” according to the CDC. But epidemics don’t affect people on a global scale. The outbreak is confined to a specific area or even an entire country, but an epidemic isn’t as widespread as a pandemic.

A pandemic, meanwhile, is defined by the CDC as “an epidemic that has spread over several countries or continents, usually affecting a large number of people.” Basically, a pandemic is like an epidemic but spread further around the globe.

Previous pandemics

  • The Spanish Flu pandemic of 1918: This was the most destructive pandemic of the 20th century. It was caused by an H1N1 virus, and it had a mortality rate of 2.5%, killing as many as 50 million people worldwide and 675,000 in the U.S. Unlike most influenza, which has a deadlier effect on the very young and the very old, the Spanish flu was most deadly for people between the ages of 20-40.
  • The H1N1 swine flu pandemic of 2009: After it was first detected in the U.S., the virus spread and killed between 150,000-575,000 people globally (about 12,500 in the U.S.). According to the CDC, the virus “contained a unique combination of influenza genes not previously identified in animals or people,” and it was deadlier for people younger than 65 years old. In most seasonal influenza epidemics, people who are 65 years or older account for 70-90% of the deaths. For H1N1, 80% of deaths globally were in people younger than 65. The CDC believes that anomaly is due to many older people having an antibody against the virus because they had been exposed to an H1N1 virus earlier in their lives.

Previous epidemics

  • Smallpox: It was a disease that could kill three out of 10 people, and leave physical scars on the people who survived), and in the 16th century, Europeans moving to what is now the U.S. spread the disease to the native people already living there. Historians believe that smallpox wiped out as much as 90% of the indigenous people living in North and South America.
  • The typhoid fever epidemic in New York in 1906: Mary Mallon—better known as Typhoid Mary—shoulders some of the blame for this outbreak in New York City 114 years ago. She was a cook in the residence of a rich New York banker, and she apparently had a moderate form of the virus (she was asymptomatic). She proceeded to contaminate everything around her, through her cooking and during her trips outside of the home in Manhattan. The NIH said 3,000 New Yorkers were infected, and “probably Mary was the main reason for the outbreak.” At the time, the mortality rate of typhoid fever was 10%, and she’s believed to have infected more than 120 people on her own before she was quarantined.
  • The SARS outbreak of 2003: This was the first major disease scare of the 21st century, and though it only infected 8,000 people in 26 countries, its mortality rate of 10% was high. This was not classified a pandemic because it was contained relatively successfully.

Sources: WHO, CDC, U.S. News and World Report, Stanford, National Institute of Health, PBS

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