A Century of Flu Pandemics

The Spanish Flu was the worst but by far not the only flu pandemic in the 20th century. This page offers a quick overview of two more pandemics that struck in the past century. It also explains the swine flu scare that is frequently quoted as a bad example of government intervention in the discussions about appropriate responses to the 2009 swine flu pandemic.

On this page…
  The Asian Flu, 1957-58 »
  The Hong Kong Flu, 1968-69 »
  The Swine Flu Scare, 1976 »

The Asian Flu, 1957-58

A new strain of influenza (H2N2) emerged in the Far East, killing between one and two million people worldwide, about 70,000 of them in the United States.1

After identifying the viral strain causing the outbreak in February, scientists were able to develop a vaccine by August. During that summer, there were small pockets of infection throughout the United States. But when children went back to school in September, the pandemic took hold as they spread the disease in their classrooms and took it home to their families.2

The rate of infection eased by Christmas, but in the new year a second wave targeted the elderly in particular. This pattern of successive waves of illness affecting different populations is characteristic of flu pandemics.

The Hong Kong Flu, 1968-69

With a death toll of 750,000 worldwide and 33,800 in the United States, the Hong Kong Flu strain (H3N2) caused the mildest pandemic in the 20th century.

The illness was first detected in Hong Kong early in 1968 and made it to U.S. shores in September. But the disease did not peak in this country until late December, a time when many children were on vacation from school and thus less likely to transmit it.

In addition to this fortuitous timing, a higher mortality rate was probably averted because of the similarity of the Hong Kong virus to the Asian Flu virus that had been circulating since 1957. (Although the H antigen was different, both strains shared the same N2 antigen.) Many people may have retained some immunity to the new strain.

Medical care also improved in the 1960s along with the availability of more antibiotics to combat the secondary bacterial infections that often plague flu victims.3

The Swine Flu Scare, 1976

The ability of a virus to frighten health authorities and the general public was perfectly demonstrated with the emergence of a flu-like illness at Fort Dix, New Jersey. Federal researchers isolated a flu virus with the same H1N1 antigenic signature as the Spanish Flu. Thirteen soldiers became seriously ill, one young man died.4

With vigilance in mind, the Centers for Disease Control recommended a massive vaccination campaign. Within 10 weeks, 40 million Americans were inoculated.5

That so many people were vaccinated so quickly was an impressive public health achievement. But any satisfaction with this effort quickly dissipated with reports of temporary paralysis, and death, among the newly injected. By January 1977 more than 500 cases of Guillain-Barré syndrome were counted, with 25 deaths.6

The so-called "swine flu” never spread beyond the Fort Dix area, and later research showed that it was much less deadly than the Spanish Flu.7 The panic over a pandemic that never materialized, the rush to vaccination, and the serious side effects provide a cautionary historical backdrop for public health officials today.

Subtypes of 20th Century Pandemics

Spanish Flu, 1918 H1N1
Asian Flu, 1957/58 H2N2
Hong Kong Flu, 1968/69 H3N2

Source: Center for Nonproliferation Studies


  1. Monterey Bay's Pandemic Flu Watch, History.

  2. U.S. Department of Health & Human Services, National Vaccine Program Office: Pandemics and Pandemic Scares in the 20th Century, revised February 2004.

  3. U.S. Department of Health & Human Services, op. cit.

  4. Joel C. Gaydos, Franklin H. Top Jr, Richard A. Hodder, “Swine Influenza A Outbreak, Fort Dix, New Jersey, 1976,” Emerging Infectious Diseases 12:1, (January 2006): 23-28.

  5. Richard E. Neustadt, Harvey V. Fineberg, The Epidemic That Never was: Policy Making in the Swine Flu Scare, Vintage Books, 1983.

  6. Elissa A. Laitin, Elise M. Pelletie, “The Influenza A/New Jersey (Swine Flu) Vaccine and Guillain-Barré Syndrome: The Arguments for a Causal Association,” December 1997.

  7. U.S. Department of Health & Human Services, op. cit.

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