Introduction to Influenza
Influenza is a common disease with uncommonly lethal potential. In the United States alone, a typical flu season kills more than 30,000 people each winter, according to the CDC. A serious worldwide outbreak—or pandemic—of flu could lead to millions of deaths around the globe as well as breakdowns in the economy, social order and everyday life.
In the past decade, officials around the world have tried to prepare nations and individuals for the next flu pandemic. There has never been any doubt it will happen—influenza pandemics date back to Hippocrates and occurred three times in the 20th century—but there has been significant debate over how severe the next pandemic will be.
Now we know that at least in its first wave, the first influenza pandemic of the 21st century caused only mild disease in most people. Additionally, mortality rates were not higher than during seasonal influenza. The second wave of the pandemic started equally mild. Winter 2009-10 will show how the story continues, what the impact of a mild pandemic might be and if the strain will change into a more lethal version.
This chapter provides a basic introduction to both seasonal and pandemic influenza, including the origin of the name, why seasonal influenza typically strikes in winter, and why people and officials have different things in mind when they hear the term pandemic.