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Influenza
Causes
Two types of viruses cause influenza: influenza A virus and influenza B virus. Each of these types encompasses several different strains of the virus, which are named for the place where they were first identified (for example, Hong Kong flu virus and Russian flu virus).
The unusual characteristic of the flu viruses is that once a strain has spread throughout a population, it changes in structure, or mutates, becoming capable of causing a new form of influenza. The antibodies that are produced by the body to combat the virus are no longer effective because the virus has taken on different qualities. Scientists are generally able to predict what type of altered virus to expect each year, but their predictions are not always on target, and about every ten years an entirely new strain of the virus appears.
Because influenza is thought to be transmitted by airborne particles from an infected person's respiratory tract, large numbers of people can easily contract the disease in a short period of time. Overcrowded living conditions promote the transmission of the virus. Since the flu spreads most easily when temperatures and humidity are low, most cases of influenza occur in the fall and winter.
Symptoms
Flu symptoms usually develop one to three days after exposure to the virus. Some people experience symptoms in as short a time as 18 hours after exposure. Fever, chills, headache, muscle aches, and total exhaustion can occur suddenly. Fevers associated with influenza infection generally do not exceed 104 degrees Fahrenheit, but they can rise to 106 degrees.
Frequently, people experience a dry cough and a runny or congested nose as their initial symptoms begin to subside. These respiratory symptoms worsen and remain for three to four days. The cough and fatigue may persist for two weeks or more after the other symptoms of infection have disappeared.
Treatment
In most cases, influenza cannot be cured and is treated only with measures designed to help relieve symptoms and make the patient more comfortable.
Treatment for the flu is generally the same as treatment for a bad cold or fever. Physicians recommend bed rest, extra fluids, and an aspirin substitute to reduce fever and muscle aches if needed. Because an association has been established between aspirin use during a viral infection and Reye's syndrome in children, it is recommended that aspirin not be given to a child who has or is suspected of having influenza. Acetaminophen, however, has not been linked to Reye's syndrome and can be used.
Nasal sprays or drops (when used sparingly so that nasal tissues are not damaged) and cough medicines can help relieve coldlike symptoms. Using a vaporizer in the patient's bedroom to add moisture to the air helps relieve congestion.
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