Influenza is an infectious disease of the respiratory
             tract caused by the specific virus of the genus
             Orthomyxovirus. It is a highly contagious infection, that
             affects all age groups. Influenza is most dangerous in
             the very young, the elderly and people with chronic
             diseases. It is probably the last remaining world wide
             infection of humans. Influenza is also known as the flu
             The flu results from three different types of the
             virus Myxovirus influenza. A person can catch it by
             inhaling respiratory droplets throughout the air from an
             infected person or just by drinking out of the same
             glass. The virus invades the respiratory tract, causing
             inflammation. There are three virus strains. Type A is
             the most prevalent. It strikes every year, undergoing
             major changes that cause epidemics every three years.
             Type B also strikes annually, but only causes epidemics
             every four to six years. Type C causes only sporadic
             cases. A person infected with type A or type B becomes
             immune to that strain but is still susceptible to the
             infection with new strains of the virus. New forms of the
             type A virus arise throughout the world. These strains
             have caused the worldwide spread of influenza. Type A
             influenza caused the Spanish flu of 1918 which was one
             of the most destructive outbreaks of disease ever
             recorded, killing 20 million people in a few months.
             Since Influenza is caused by a virus, it must run its
             course, usually lasting seven to ten days. Symptoms
             appear about 24 to 49 hours after a person is exposed
             to the flu virus. They include sudden chills, a high
             temperature, headache, malaise, muscle ache, cough,
             and occasionally, laryngitis, hoarseness, eye
             inflammation, runny nose and nasal congestion. These
             symptoms usually go away in three to five days, but a
             cough and weakness may continue. Influenza may also
             worsen chronic lung disease and cause other serious
             Early cases of the fl...