Influenza's Impact on the Biosphere
Influenza pandemics have had a substantial effect on human mortality. The Spanish flu pandemic of 1918–1919, for example, caused a huge increase in the mortality rate due to infectious diseases. Since 1980, the mortality rate has been increasing primarily due to HIV but is also the result of respiratory infections in the increasing number of elderly people.
After researching flu pandemics of the 19th century, scientists have discovered four main patterns in which the disease usually spreads. Patterns of rapid frontal diffusion over a large area, or "massive frontal movements," are associated with high mortality rates. The "multiple sequester" pattern entails outward expansion from a few small areas during a flu season, but usually does not spread as far and entails lower mortality rates."Seasonal epicenter relocation" is similar to the multiple sequester, but involves the movement of the outbreak centers every season. The last type of outbreak, the "herald explosion," encompasses the three other main types of outbreaks and hits both initially during the spring and again later in the fall or winter of the same year and has high mortality rates. The pandemic of 1842-43 is a good example of this type of outbreak.
At this point in time, the threat of an avian flu pandemic is unlikely because its main strains are still not capable of physically interacting with the human cells in the respiratory tract. However, if such a mutation were to occur it could prove very deadly; the flu virus mutates very quickly making it near impossible to kill with modern vaccinations and medicine. Scientists are also unsure what strain of flu will arise each year, making it hard to predict what vaccination to administer with each new season. However, research is being done to find new antivirals or even a DNA-based vaccine that will wipe out the disease forever.