Sign Up Now For
Our FREE E-mail Newsletter

In each issue of HEALTHbeat:

  • Get trusted advice from the doctors at Harvard Medical School
  • Learn tips for living a healthy lifestyle
  • Stay up-to-date on the latest developments in health
  • Receive special offers on health books and reports
  • Plus, receive your FREE Bonus Report, Living to 100: What's the secret?

[ Maybe Later ] [ No Thanks ]

Check out these newly released Special Health Reports from Harvard Medical School
Learn How

New Releases

You can't buy good health but you can buy good health information. Check out these newly released Special Health Reports from Harvard Medical School:

Stages of an influenza pandemic - Harvard Health Publications

Home > Flu Resource Center > Stages of an influenza pandemic

Stages of an influenza pandemic

There were three pandemics of human influenza in the 20th century. By far the worst was the 1918 “Spanish flu,” which gained virulence in the close quarters of World War I trenches, hospitals, and transports, and circled the globe, killing more than half a million people in the United States and many millions worldwide in a single year.

Stages of an influenza pandemic

As part of its preparedness plan, the World Health Organization has defined the stages of a pandemic. As of June 11, 2009, we are in phase 6.


Pandemic alert


Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

Phase 6: Our current phase

New virus in animals. Human risk is low.

Circulating animal virus poses higher risk of human cases.

Human infection(s) have occurred, but no or very limited human-to-human transmission.

Localized cluster(s) of human cases; increased evidence of human-to-human transmission.

Larger cluster(s) of human cases; evidence of significant human-to-human transmission.

Increased and sustained human-to-human transmission in a general population.

Sources: World Health Organization; Centers for Disease Control and Prevention.

With past pandemics, doctors couldn’t do much. The outbreaks took everyone by surprise, rapid diagnosis was not possible, and there were no antiviral drugs. Fortunately, a lot has changed. We have new technologies for diagnosing and treating the disease, and we know more about how to contain it in birds. Surveillance methods are in place, and communications are faster. Health authorities are also more knowledgeable about the spread of disease; scientists have a better understanding of viruses; and researchers can use computers to model outbreaks and test response plans. We have antiviral medications that can ease the symptoms of influenza and reduce its spread, and vaccines are being tested.

Such advances don’t mean we can become complacent — vigilance is as critical as preparedness when a pandemic looms. But it may be reassuring to know that some important strategies are in motion. There are also things individuals can do to help protect themselves. For information on preventing flu infection, visit the Harvard Health Flu Resource Center.


Low Back Pain Special Report

Viruses and Infectious Diseases: Protecting yourself from the invisible enemy

Have you ever wondered whether you are truly protected from infectious diseases ranging from the common cold to more deadly threats like rabies or bird flu? This report describes the most up-to-date information on infectious disease and how to protect yourself from everything from stomach flu to HIV/AIDS. Read more »