Influenza (the flu) is caused by the influenza virus. According to the Centers for Disease Control (CDC), 5 to 20 percent of Americans are infected by the virus every year, causing about 200,000 hospitalizations and 36,000 deaths. The virus typically attacks the respiratory system, where it can cause a viral pneumonia in severe cases or destroy the lungs enough to allow the development of secondary bacterial pneumonia.
The virus is usually transferred by droplet infection, with sneezing, coughing or spitting. Soiled material or napkins and surfaces can also serve as avenues of infection. Touching infected hands to the eyes, mouth or nostrils transfers the virus into the body.
How the Virus Reproduces
The influenza virus sticks to the cells lining the respiratory tract by means of a special protein called hemagglutinin. On contact with the cells, the virus is drawn into the cell and sheds its coat. The viral genetic material (RNA) enters the nucleus of the host cell, and initiates the replication of viral RNA and production of enzymes that hijack the mechanisms of the cell to produce other viral components. These viral components include enzymes which further the viral domination of the cell.
The produced viral components including genetic materials, enzymes and cell wall components are assembled close to the cell membrane into infective units. These are released from the cell, leaving the cell intact, or released as the cell dies from viral activity and bursts. Maturation of the infective units takes place as they leave the cell or later as they float around in extracellular fluid.
Large numbers of the virus are produced even before widespread destruction of the cells of the respiratory tract. Thus, the infected individual can spread the virus even before he actually feels sick. Typically, the infected person can spread the infection from one day before, to five to seven days after the onset of symptoms.
Prevention and Treatment
Vaccination is the backbone of prevention. Vaccination allows the body to build up sufficient immunity to prevent an infection, or a severe infection if one does occur.
Proper hygiene is recommended to further limit the spread of the infection. Proper coverage of the face when coughing or sneezing is encouraged as is the disposal of soiled napkins. Regular hand washing and use of alcohol based sanitizers also reduce spread of the infection. Proper washing of soiled clothing and linen with regular hand-washing while handling such laundry will reduce the chances of contacting the infection amongst those taking care of the sick.
Antivirals like Relenza, Tamiflu and amantadine are used in the treatment of the flu. These reduce the severity of illness, minimize the chances of complications and shorten the course of the illness.