Influenza, or the "flu", is an infection of the respiratory tract (breathing tubes and lungs), caused by the influenza virus. In some persons, complications of influenza can be severe, including pneumonia.
Pandemic influenza is a widespread outbreak of disease from a new influenza A virus that is unlike past influenza viruses. Because people have not been infected with a similar virus in the past, most or all people will not have any natural immunity (protection) to a new pandemic virus.
A flu pandemic has little or nothing in common with the annual flu season. Pandemic flu would be a new strain and a much more serious flu virus. Humans would have no natural resistance to a new strain of influenza. Also, there is a vaccine for seasonal flu, but there is no vaccine available at this time for pandemic flu.
Because most or all people would not have immunity to a new pandemic virus, large numbers of persons around the world can be infected. If the pandemic virus causes severe disease, many people may develop serious illnesses.
Once a pandemic virus develops, it can spread rapidly, causing outbreaks around the world. The U.S. Centers for Disease Control and Prevention (CDC) predicts that as much as 25% to 30% of the U.S. population could be affected.
Southeastern Idaho Public Health is working with federal, state, and local government agencies to respond to pandemic influenza if an outbreak should occur. The Idaho Pandemic Influenza Response Plan identifies Idaho-specific activities that may occur during a flu pandemic. Governments around the world are preparing for the possibility of a pandemic outbreak under the leadership of the World Health Organization.
It may not be possible to prevent or stop a pandemic once it begins. A person infected with influenza virus can be contagious for 24 hours before the onset of symptoms, and for seven days thereafter, making it extremely easy for the virus to spread rapidly to large numbers of people.
Although the federal government is stockpiling medical supplies and antiviral drugs, no country in the world has enough antiviral drugs to protect all its citizens. Antiviral drugs may be used to treat severe cases or prevent additional cases as long as supplies are available. Antiviral drugs might also be prioritized for people who work in essential occupations, such as health care workers.
There currently is no vaccine to protect humans against a pandemic influenza virus because it is not known which virus will spark the next pandemic. However, vaccine development efforts are under way to protect humans against a pandemic influenza virus that might develop from the current bird flu virus in Asia, A/H5N1. (See information on bird flu below).
Influenza pandemics occur naturally. There were three pandemics in the 20th century. The pandemic of 1918-19 was the most severe pandemic on record, in which 50 million or more persons around the world died, including approximately 650,000 Americans.
It is not possible to predict accurately when influenza pandemics will occur or how severe they will be. However, the current outbreak of avian influenza in Asia has influenza experts concerned that a pandemic could be developing.
New human influenza viruses arise from bird influenza viruses that then change to a form that can infect humans and spread readily from person to person. The current bird flu outbreak in Asia is caused by a type of influenza A virus called "H5N1." The H5N1 outbreak among domestic chickens and ducks in Asia is widespread and uncontrolled. Human infections and deaths due to the avian H5N1 virus have occurred, although the virus has at this time not developed the ability to pass easily from person to person and cause outbreaks in humans.
The reported symptoms of bird flu in humans have ranged from typical influenza-like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections (conjunctivitis), pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications.
Information on this page has been adapted from Public Health - Seattle & King County, August 17, 2005.
