Stopping and Preventing Influenza Pandemics
A vaccine probably would not be available in the early stages of an influenza pandemic. When a new vaccine against an influenza virus is being developed, scientists around the world work together to select the virus strain that will offer the best protection against that virus. Manufacturers then use the selected strain to develop a vaccine. Once a potential pandemic strain of influenza virus is identified, it takes several months before a vaccine will be widely available. If an influenza pandemic occurs, the U.S. government will work with many partner groups to make recommendations guiding the early use of available vaccine.
There are four different antiviral medications (amantadine, rimantadine, oseltamivir, and zanamivir) that are approved by the U.S. Food and Drug Administration (FDA) for the treatment and/or prevention of influenza. All four drugs usually work against influenza A viruses. However, the drugs may not always work, because influenza virus strains can become resistant to one or more of these medications.
For example, the influenza A (H5N1) viruses identified in humans in Asia in 2004 and 2005 have been resistant to amantadine and rimantadine. Researchers are continuing to monitor avian viruses for resistance to other antiviral medications.
Many scientists believe it is only a matter of time until the next influenza pandemic occurs. The severity of the next pandemic cannot be predicted, but modeling studies suggest that the impact of an influenza pandemic on the United States could be substantial.
In the absence of any control measures (vaccination or drugs), it has been estimated that in the United States, a "medium–level" pandemic could cause:
- 89,000 to 207,000 deaths
- 314,000 to 734,000 hospitalizations
- 18 to 42 million outpatient visits
- 20 to 47 million cases of illness.
Between 15 percent and 35 percent of the U.S. population could be affected by an influenza pandemic, and the economic impact could range between $71.3 and $166.5 billion.