Influenza - Pandemic

Last Updated: July 31, 2018
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​Pandemic flu is a human flu that causes a global outbreak of illness. Because most people have no immunity to a pandemic virus, infection rates during a pandemic are expected to be higher than those during outbreaks of seasonal flu.

Woman sneezing into a tissue

Pandemic Flu Facts 

  • One hallmark of influenza viruses is that they are constantly changing. If a non-human (novel) influenza virus gains the ability for efficient and sustained human-to-human transmission and spreads globally, an influenza pandemic occurs.
  • Given the virus is new and there is little natural immunity, the disease can easily spread from person to person.
  • On average, pandemics occur about every 30 to 40 years. Three pandemics occurred in the previous century: "Spanish influenza" in 1918, "Asian influenza" in 1957, and "Hong Kong influenza" in 1968. The most recent is the outbreak of novel H1N1 influenza in 2009.
  • Since most people will have no immunity to the pandemic virus, infection and illness rates during a pandemic are expected to be higher than those during seasonal outbreaks of normal flu.
  • Pandemic flu is spread similarly to seasonal flu, from person to person through sneezing and coughing or through contact with objects such as doorknobs, eating utensils and telephones that are contaminated with flu viruses.
  • The flu is a virus and antibiotics are not an effective form of treatment. Antibiotics are, however, useful in treating secondary bacterial infections that can result from or occur with the flu
  • CDC's pandemic preparedness efforts include ongoing surveillance of human and animal influenza viruses, risk assessments of influenza viruses with pandemic potential, and the development and improvement of preparedness tools that can aid public health practitioners in the event of an influenza pandemic.

Pandemic Influenza: 2009 H1N1 Influenza

  • In 2009, the H1N1 virus emerged and caused the first global pandemic in more than 40 years and resulted in substantial illness, hospitalizations and deaths.
  • This virus was originally referred to as "swine flu" because laboratory testing showed that many of the genes in this new virus were very similar to influenza viruses that normally occur in pigs (swine) in North America. Further study, however, has shown that this new virus is very different from what normally circulates in North American pigs.
  • On August 10, 2010, the World Health Organization (WHO) International Health Regulations (IHR) Emergency Committee declared an end to the 2009 H1N1 pandemic globally.  (See H1N1 in Post-Pandemic Period.)
  • The 2012-13 seasonal influenza vaccine provides protection against H1N1 influenza.

 Pandemic Potential: Avian (H5N1) Influenza

  • The avian flu virus is an example of an influenza virus with pandemic potential.
  • Avian influenza refers to the disease caused by infection with avian (bird) influenza (flu) Type A viruses. Low pathogenic avian flu is common in birds and causes few problems in humans. Highly pathogenic H5N1 is deadly to domestic fowl, can be transmitted from birds to humans, and can be deadly to humans.
  • Most cases of avian influenza infection in humans have resulted from direct or close contact with infected birds or surfaces contaminated with secretions and excretions from infected birds. You cannot get avian influenza from properly handled and cooked poultry and eggs.
  • On April 17, 2007, the U.S. Food and Drug Administration (FDA) announced its approval of the first vaccine to prevent human infection with one strain of the avian influenza (bird flu) H5N1 virus. The vaccine has been purchased by the federal government for the U.S. Strategic National Stockpile; it will be distributed by public-health officials if needed (see FDA Approves First U.S. Vaccine for Humans Against the Avian Influenza Virus H5N1External Link). For information about other H5N1 and pandemic flu vaccine research activities visit Flu.gov - Vaccine ResearchExternal Link.

Preventing the Flu

Ways to prevent catching and spreading the flu include:

  • Clean your hands often with soap and warm water or alcohol-based hand cleaners. Avoid touching your eyes, nose
    or mouth.
  • Use a tissue to cover your mouth and nose when you sneeze or cough then put used tissue in the waste basket. If a tissue is not available, then sneeze or cough into the inside of your elbow, not your hand.
  • Avoid close contact with people who are sick and keep your distance or stay home if you are sick.

Health information products (brochures, posters, etc.) on influenza are available online in the APHC Health Information Products eCatalog.


Resources - Pandemic Influenza Guidance, Recommendations and Policies



General/Family Members

Additional Information on Pandemic Flu


Sources: Center for Disease Control and Prevention (CDC); Flu.gov; World Health Organization