Brenda Andrews, age 12, of Biloxi, Miss., for her question:
CAN FLU BE PREVENTED?
The disease commonly called flu is technically called influenza, and it is caused by the influenza virus. Health authorities try to prevent the spread of the flu by means of vaccination.
Most influenza vaccines consist of killed influenza viruses. These vaccines offer some protection but are not as effective as scientists would like them to be.
During the mid 1970s, vaccines made with live viruses were developed and became available in some parts of the world. Scientists believe such vaccines may offer better protection than killed viruses vaccines do. It may be that one day flu will be completely under control, thanks to a vaccine.
We all know the symptoms of the flu: chills, fever, headache, aches in the joints and weakness. The symptoms usually disappear in about a week or 10 days.
Sometimes the flu will lower a person's resistance so that secondary infections, such as bacterial pneumonia, follow the influenza.
Influenza is mainly a respiratory disease. The virus is inhaled and comes in contact with cells of the upper air passages. It penetrates the cells that line these passages and reproduces within them. In time, new influenza viruses are released from the infected cells and infect other cells along the respiratory tract.
Influenza may be spread deep within the lungs and to other parts of the body. The virus may also be carried away in exhaled air and infect other people.
People develop immunity or resistance to influenza viruses and prevent them from infecting cells. However, the virus may change its chemical composition so that the antibodies no longer work. New kinds of antibodies must then be formed by the cells of the body.
Treatment of flu patients consists largely of combating the secondary infections which cause most of the deaths associated with influenza. Doctors control these infections with antibodies'and other drugs.
Cold weather does not directly cause influenza, as many people believe. But influenza outbreaks do occur most frequently in winter in temperate zones. These outbreaks are thought to be related to the crowding of people indoors in cold weather. In such crowded situations, the virus has a greater chance than usual to spread from one person to another.
Flu has a tendency to occur in epidemics. Each new outbreak of the disease is caused by a virus slightly different from the earlier ones.
Scientists often name the different strains or types of the virus after the place where the strain was first identified. For example, Asian flu was first identified in Asia, and it later spread to every corner of earth.
One of the worst global epidemics of influenza occured in 1918 1919. About 20 million persons, including more than 500,000 Americans, died in this epidemic.