The History of Influenza
Deadly pandemics, health crises, scientific discoveries, vaccine innovations and disease prevention.
Explore a historical timeline of major influenza events.
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Origins of influenza
When did the influenza virus first infect humans? Some scientists hypothesize that humans probably acquired influenza when they began to domesticate animals like birds and pigs. The rise of agriculture and permanent settlements provided ideal conditions to trigger a flu epidemic.
Did you know?
When an infectious disease becomes zoonotic, it can jump from a non-human animal to a human. Contact with domestic, agricultural or wildlife animals can sometimes transmit deadly pathogens and trigger an outbreak.
Early evidence of influenza
While the flu has most likely been around for ages, there are no definitive historical records. In his sixth book of “Epidemics,” the Greek physician Hippocrates describes a highly contagious disease with flu-like symptoms. Modern doctors believe this may be the first reference of influenza.
"La Influenza" Is Coined
La influenza comes from Italian, meaning "visitation" or "influence."
In 1357, people called an epidemic in Florence, Italy “influenza di freddo,” which translates to “cold influence.” This may be a reference to the possible cause of the disease.
Many astrologers in the Middle Ages believed that the periodic return of the disease was related to the "influence of heavenly bodies" or "influenza di stelle," meaning "influence of the stars."
The first flu pandemic
Most epidemiologists agree that the 1580 influenza outbreak is the earliest recorded flu pandemic. It began in Asia during the summer before spreading to Africa, Europe, and eventually across the seas to the Americas. While the total death toll is unknown, it killed 8,000 people in Rome.
18th to 19th Century
The first influenza pandemic of the 18th century started in Russia. It spread throughout Europe within six months and the world within three years.
After starting in China, this influenza outbreak spread to Russia, eventually reaching Europe and North America over the next year. At the height of the pandemic, 30,000 were infected every day in St. Petersburg.
This pandemic spread by ships from China to the Philippines, India and Indonesia. After crossing Russia to Europe, it eventually reached North America. While the mortality rate was low, it impacted 20%–25% of the population.
The world's first vaccine
Can an infection from cowpox produce immunity to smallpox?
On May 14, 1796, British physician and scientist Edward Jenner tested this hypothesis and pioneered the first vaccine. He inoculated an 8-year-old boy named James Phipps with pus scraped from cowpox blisters on a milkmaid's hands. The boy fell ill with a mild case of cowpox but fully recovered. In July, Jenner inoculated Phipps with scabs of smallpox. The boy remained healthy and had developed immunity.
Jenner's method was eventually called vaccination. “Vacca” is the Latin word for cow.
Did you know?
Inoculation has been around for hundreds of years. There’s evidence that the Chinese and Indians used smallpox vaccination as early as the 16th century.
First laboratory vaccine
Louis Pasteur produced a vaccine for chicken cholera called Pasteurella Multocida. It is celebrated as the first laboratory-developed vaccine.
Pasteur was studying fowl cholera and injecting chickens with live bacteria. He accidentally stumbled on a great scientific discovery when his assistant left out a fresh culture of bacteria over a holiday. Upon their return to the lab, Pasteur discovered exposure to oxygen weakened the bacteria so that chickens could survive infection and develop immunity.
First modern flu pandemic
One of the deadliest pandemics in history, the so-called Russian Flu infected 40% of the world’s population and killed about 1 million people. While it’s the last flu pandemic of the 19th century, it is the first to rapidly spread around the whole world due to the modern transport infrastructure of railroads and transatlantic sea travel.
The 1918 influenza outbreak was the deadliest pandemic of the 20th century.
About one-third of the world’s population was infected and 20 million to 50 million people were killed.
After reports in Europe, Asia and the United States, it rapidly spread around the world.
It was caused by a new strain of the influenza A virus that started in birds (H1N1).
The average life expectancy in the United States dropped by about 12 years.
Did you know?
The Spanish Flu did not originate in Spain. During World War I, many countries were suppressing news of the pandemic to preserve morale. Because Spain was neutral during the war and freely reporting on the pandemic, many concluded it originated in Spain.
Halting the spread
At the time, there were no vaccines or drugs to treat influenza. People got very sick, very quickly. Hospitals were overwhelmed. Many communities imposed quarantines and closed churches, schools, and public spaces. The public used gauze masks to stop the spread of the disease.
Protecting the public health
How do you control a deadly contagious disease in an era of mass transportation, crowded cities and world war?
Implementing social distancing measures played a big role in reducing the spread. Cities that acted early and sustained preventive measures longer suffered lower death rates.
Influenza virus isolated
The significant losses endured in the 1918–1919 pandemic inspired a period of great scientific research and discovery. In the 1920s, some scientists started to suspect that bacteria were not the real cause of influenza disease.
In 1933, scientists at the National Institute for Medical Research in London isolated the influenza A virus from nasal secretions of infected human patients. This discovery would lead to the innovation of inactivated vaccines in the late 1930s and 1940s.
Region: North America
Influenza vaccine approved
The immense loss of soldiers during the 1918 pandemic made the flu vaccine a priority for the U.S. military. The development of the first inactivated flu vaccine was led by Thomas Francis, Jr., and Jonas Salk of the University of Michigan. Their vaccine used fertilized chicken eggs — a method still used today to produce most flu vaccines. The first influenza vaccine was approved in the United States for military use in 1945 and civilian use in 1946.
Region: North America
WHO creates first system for surveillance
During the seasonal flu epidemic of 1947,
small changes in the composition of influenza viruses had made existing vaccines ineffective.
The World Health Organization (WHO) Influenza Centre was established in 1948 to identify new influenza viruses and
control the spread of disease.
In 1952, the WHO launched the first system for the surveillance of circulating influenza virus strains. This helped researchers to determine the composition of seasonal influenza vaccines.
The 20th century saw two more influenza pandemics: the Asian Flu of 1957 and the Hong Kong flu of 1968.
Asian Flu pandemic
A new influenza A virus struck East Asia in 1957, unleashing a devastating global pandemic. First reported in Singapore, it quickly spread to Hong Kong in April and the United States by summer. The estimated number of deaths was 1.1 million worldwide and 116,000 in the United States. The rapid development of a vaccine and the availability of antibiotics limited the spread and death toll.
Hong Kong Flu
The 1968 global outbreak of influenza originated in China. The virus was highly contagious — in Hong Kong, 500,000 cases of illness were reported within two weeks. It quickly spread throughout Southeast Asia and reached the United States within months, transported by soldiers returning from Viet Nam.
Experts suspect that it evolved from the strain of influenza that caused the 1957 pandemic. Many exposed to the 1957 virus retained immunity against the 1968 virus. The pandemic killed between one and four million people globally.
20th to 21st Century
Idoxuridine, the first antiviral drug, was approved. Since this scientific breakthrough, antiviral drugs have helped millions people around the world.
Scientists developed the first trivalent flu vaccine, which protected against three different strains of influenza. Today, quadrivalent flu vaccines are commonly used every flu season to protect against four different flu strains.
Did you know?
The Messenger RNA (mRNA) vaccines teach our cells how to make a protein that will trigger an immune response inside our bodies.
The first study is published demonstrating mRNA vaccination in mice.
New studies show that mRNA vaccines induce long-lived and protective immunity to influenza.
A new influenza H1N1 virus was detected in the United States in April 2009 before quickly spreading worldwide. Swine flu primarily affected children and young adults who had no immunity to the new virus. There were 60.8 million cases and and 12,469 deaths in the United States alone. Due to the rapid response of the CDC and WHO, a vaccine was quickly developed. The first doses were administered on October 5 of the same year.
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Beyond Flu to Coronavirus
Between 2019 and 2020, flu vaccines have prevented about 7.5 million illnesses, 3.7 million doctor visits, 105,000 hospital stays and 6,300 deaths in the U.S. alone.
On January 2020, scientists began work on the vaccine in response to the COVID-19 pandemic.
Because organizations like the National Institutes of Health (NIH) have been researching coronaviruses for years, scientists were able to innovate much faster.
On August 23, 2021 the U.S. Food and Drug Administration approved the first COVID-19 vaccine.
How do you create a better flu vaccine?
Researchers have been exploring new mRNA vaccine technology which can provide biological instructions for cells to produce proteins that trigger an immune response. A mRNA influenza vaccine could enable a faster response to outbreaks and potentially save more lives.
How Flu Spreads
How Can You Prevent the Flu?