FLU

Also known as influenza, the flu is an infection of the throat, airways and lungs and causes more severe symptoms and complications than the common cold.

Most adults have about two to four colds a year, while an average of 200,000 people are hospitalized yearly as a result of influenza and as many as 36,000 Americans per year die from the flu and its complications.

According to Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota in Minneapolis, all influenza viruses originate in wild birds. Pandemic variants often occur when a bird or avian virus infects pigs. The virus may then recombine, or mutate, to form a new virus that is able to infect humans and possibly pass from person to person.

The disease we consider the normal flu, which tends to hit America every winter, is left over from the 1968 pandemic.

There are two main ways the flu virus mutates or evolves: antigenic shift and antigenic drift.

Antigenic shift is when two different strains of the flu combine to form a subtype, or a combination of the two originals. This only occurs in type A influenza, because it affects multiple species (birds, pigs and humans, for example). Antigenic drift is the change of a virus over time as it tries to evade the immune system of the organism it is infecting. This is why a new flu vaccine has to be prepared each year.

The symptoms of the flu are similar to the common cold, but are much more severe and can be life threatening. Common symptoms include fever, body aches and pains, dry cough, nasal congestion, sneezing, sore throat, chills, fatigue and stomach symptoms (nausea, vomiting, diarrhea).

Further complications from the flu include bacterial pneumonia, dehydration and an exacerbation of other existing medical conditions.

The best way to prevent the flu? A flu shot. Vaccines prevent the person inoculated from getting the disease by simulating a weak infection, allowing the body to create antibodies for that disease that are used to fight the flu if the person is actually infected.There are two types of vaccines. The first is the widely known flu shot, containing an inactivated virus. There is also a nasal spray vaccine that contains weakened live influenza viruses instead of killed viruses. Both forms of the vaccine contain three vaccine strains -- two types of influenza A and one B.

Anti-viral drugs interfere with a virus' ability to reproduce, so they can aid a person who is already infected with the disease by reducing the duration of the symptoms and complications associated with the disease. But they do not cure influenza outright. An upside to anti-viral drugs is that they are not specific for a particular strain of the flu (unlike a vaccine), and can be used to combat a new strain before a vaccine could be produced. The four antiviral drugs (amantadine, rimantadine, zanamavir and oseltamivir) approved for use in the United States are prescription only.