An epidemic is a breakout of disease in a community within a short period. A pandemic is an outbreak of disease over a wide area or worldwide. Most pandemics are viral, although bacteria and parasites can also cause major outbreaks. Regardless of the cause, many of the pandemic deaths result from sepsis.

COVID-19 is the fifth major pandemic to hit in the past 100 years, but there have been smaller ones too.

1918 pandemic first found among the military

In 1918, the world was hit by an H1N1 influenza virus. Experts don’t know for sure where the virus started, but it swept across the globe, killing at least 50 million people; about 675,000 people in the United States. Unlike most flu strains, H1N1 killed more young people than older ones. Since this virus struck before the advent of antibiotics, many died of sepsis, from secondary bacterial infections like pneumonia, caused by the flu.

The 1918 pandemic hit the world with three waves, the first wave, which occurred in spring 1918, the second wave in the fall, and a third in the winter, lasting into spring 1919. The second wave was the deadliest.

According to the Centers for Disease Control and Prevention (CDC), this pandemic killed more people than everyone – civilian and military – who died in World War I.

H2N2 virus pandemic, 1957

Thirty-nine years after the H1N1 pandemic, the world saw another one. This H2N2 flu virus killed 1.1 million people across the world; 116,000 in the U.S. At this time, doctors had antibiotics to help treat patients who developed secondary bacterial infections and sepsis, which kept the death rate lower than it might have been, perhaps similar to the 1918 numbers. This flu also affected more young people, pregnant women, and the elderly.

The first wave wasn’t as severe in the U.S., but the second wave hit hard, making up most of the deaths.

H3N2 virus pandemic, 1968

Yet another influenza virus struck the world in 1968. This one hit older people the hardest; they made up the largest number of people who died. About 1 million people died worldwide, with about 100,000 in the U.S.

While H3N2 didn’t kill as many people as the two previous flu pandemics, there was a lot of fear surrounding this one because it seemed to be particularly infectious. It took only two weeks to spread from its origin to neighboring countries, and by the end of the year, the virus was found throughout the world. Again, the second wave was the deadliest.

H1N1 virus pandemic, 2009

The most recent pandemic before COVID-19 struck, was the H1N1 influenza pandemic in 2009. As with the 1918 H1N1, this flu killed and injured more young people than older ones. About 80% of H1N1 deaths were among those under age 65. The CDC estimates 151,700-575,400 people worldwide died in the first year. Again, like 1918, as well as 1957, most deaths were among younger people – about 80% of deaths.

COVID-19, 2020

Reports of COVID-19 began circulating early in 2020, but the virus was first detected in 2019, which is why it was named COVID-19.

Two other pandemics that occurred within recent memory are:

  • 1981 to present: AIDS, which has claimed about 33 million people worldwide, is still present in society today.
  • 2014-2016: Ebola, killed almost 12,000 people in Africa during these two years alone and still has outbreaks to this day.

Earlier pandemics

Ever since viruses could spread, there have been epidemics and pandemics. Historians found evidence of a virus in China in 3000 BC that wiped out a prehistoric village. And a plague occurred in Athens, Greece, in 430 BC during the Peloponnesian war, and it lasted five years. The virus spread to Libya, Ethiopia, and Egypt. Historians estimate it may have killed 100,000 seemingly healthy people.

Others include:

  • 165-180 AD: Possibly smallpox, brought by the Huns to Germany and then to Rome.
  • 250-271 AD: Rome, killing about 5,000 people
  • 541-542 AD: Byzantine Empire (Middle East to Western Europe), killing perhaps up to 10% of the population
  • 11th century: Leprosy, a bacterial infection spread throughout Europe. The disease still exists in modern time and is fatal if not treated with antibiotics.
  • 1346-1353: Asia to Europe, “the Black Death,” a plague that some suggest wiped out over half of all people in Europe. Unlike other epidemics and pandemics, this was caused by bacteria spread by fleas.
  • 1492: The Columbian Exchange, refers to smallpox, measles and bubonic plague brought from Spain to the Caribbean. AS many as 90% of the indigenous people died from these diseases as they had no immunity.
  • 1545-1548: Mexico and Central America, a viral hemorrhagic fever, but many of the victims also may have had a form of salmonella. It’s believed 15 million people died.
  • 16th century: “American Plagues” caused by diseases brought over from Europe, wiping out ancient civilizations of the Inca and Aztec.
  • 1665-1666: Great Plague of London, another outbreak of the Black Death. It killed 15% of the London population and about 100,000 people overall.
  • 1720-1723: Great Plague of Marseille lasted three years. This plague also killed an estimated 100,000 people.
  • 1770-1772: Russian Plague, which claimed another 100,000 people.
  • 1793: Philadelphia yellow fever epidemic, spread by infected mosquitoes, the epidemic killed more than 5,000 people.
  • 1817: Cholera, this was the first of seven cholera pandemics, this one killing more than 1 million people.
  • 1855: Third Plague Pandemic, a bubonic plague that killed 15 million people as it spread across China, India, and Hong Kong.
  • 1875: Fiji Measles Pandemic occurred when a Fijian chief traveled to Australia for an official state visit. His entourage contracted measles and brought the virus back to their homeland. The virus killed a third of the population, about 40,000 people.
  • 1889-1890: Worldwide flu pandemic, starting in Russia and spreading across the globe. It is considered to be the first modern flu pandemic. An estimated 13,000 people in the U.S. died during this pandemic and 1 million people worldwide.
  • 1916: Polio, started in New York City and caused 6,000 deaths, and thousands of survivors who were left with life-long disabilities, such as paralysis.


News of epidemics and pandemics can be frightening. We can’t always prevent infections. But with care and consistency with good hygiene practices, as well as not proper use of antibiotics, we can reduce our risk of becoming sick when infections spread.

Antimicrobial resistance, or AMR (also called antibiotic resistance), is a serious threat to human health. The 1918 influenza death toll was so high because many died of secondary bacterial infections. COVID-19 can cause bacterial pneumonia. If AMR becomes too prevalent, we no longer will have the means to treat these infections.


If you suspect sepsis, call 9-1-1 or go to a hospital and tell your medical professional, “I AM CONCERNED ABOUT SEPSIS.” 


Suggested Citation: Sepsis Alliance. Sepsis and Pandemics. 2022.

Updated November 7, 2022.


An epidemic is a breakout of disease in a community within a short period of time. A pandemic is an outbreak of disease over a wide area or worldwide. Most pandemics are viral, although bacteria and parasites can also cause major outbreaks. Regardless of the cause, many of the pandemic deaths result from sepsis.