Pandemic influenza

Sometimes a new strain of influenza virus emerges to which humans have no natural protection. If the new influenza virus is easily transmitted from person to person, it can result in serious disease affecting people worldwide. This is called an influenza pandemic. Influenza pandemics occurred in 1918, 1957 and 1968. The next influenza pandemic will occur when a new strain of influenza virus emerges that is easily transmitted from person to person.

What's the difference between a pandemic and a seasonal outbreak of flu?

A pandemic is caused by a new influenza A virus that most people have never been exposed to, so everyone is susceptible. Pandemic strains also often cause more serious disease. Because of this, past flu pandemics have led to high levels of illness, death, social disruption and economic loss.

Seasonal outbreaks of flu are caused by strains of flu virus similar to those of past years. Some people may have built up immunity, and there is also a vaccine for each year's flu season.

When is the next flu pandemic expected?

Three pandemics occurred in the 20th century, all of which spread around the world within one year of being detected. Of these, the pandemic of 1918-1919 was the most severe, with 50 million or more deaths worldwide.

No one can predict when a pandemic might occur, but many scientists believe it is only a matter of time before the next one arises. Experts from around the world are watching the H5N1 Avian (bird) Flu situation in Africa, Europe and Asia very closely and are preparing for the possibility that the virus may begin to spread more easily and widely from person to person.

Flu pandemics are different from many of the threats for which public health and the health care system are currently planning:

  • The pandemic will last much longer than most other emergency events and may include waves of flu activity separated by months (in 20th century pandemics, a second wave of flu activity occurred three to 12 months after the first wave).
  • The numbers of health care workers and first responders available to work can be expected to be reduced as they will be at high risk of illness through exposure in the community and in health care settings, and some may have to miss work to care for ill family members.
  • Resources in many locations could be limited because of how widespread a flu pandemic would be.

Does a flu shot protect against pandemic flu?

Current flu vaccines will not protect against a new pandemic strain of flu virus. Because it takes several months to develop and distribute vaccine for a new strain, a vaccine probably would not be available in the early stages of a pandemic. If a pandemic occurs, it is expected that the U.S. government will work with many partner groups to make recommendations to guide the early use of vaccine. Vaccines that may be effective against H5N1 virus are being developed and tested.

Will the seasonal flu shot protect me against pandemic influenza?

  • No, it won't protect you against pandemic influenza. But flu shots can help you to stay healthy.
  • Get a flu shot to help protect yourself from seasonal flu.
  • Make sure that your family immunizations are up-to-date.

Are there any other treatments for pandemic flu?

Antiviral medications can be used to treat and/or prevent influenza A viruses. However, flu strains can become resistant to antiviral medications. For example, only one antiviral medication works against the H5N1 Avian Flu virus identified in human patients in Asia in 2004 and 2005. The supply of this antiviral medication is very limited worldwide, and no pharmaceutical company in the United States manufactures it.

What should you be doing?

Protect yourself against the spread of the flu and other germs and viruses:

  • Cover your nose and mouth with a tissue when coughing or sneezing, or cough into your elbow.
  • Wash hands thoroughly and often.
  • Avoid touching eyes, nose or mouth.
  • Stay home when you are sick.
  • Visit for more information.
  • Prepare yourself and your family with planning tools - Family Pandemic Planning.