The flu is a common ailment that comes around every year. Learn about this condition and how to prevent it.
Influenza is a common infectious disease, generally occurring in the winter months in the United States. The condition is often highlighted in the media when it pertains to exotic forms of influenza, such as avian flu. The flu may be mild or severe, as exemplified by past outbreaks (e.g., flu pandemic of 1918-1919). Understanding influenza may be important in preventing future occurrences.
Virus
The flu is caused by a virus of the family Orthomyxoviridae. The structure of the virus consists of ribonucleic acid (RNA) encased in a protein capsule. Influenza A contains 10 proteins while influenza B contains 11 proteins. Hemagglutinin and neuraminidase are two of the proteins on the surface of the virus and are the basis for typing influenza strains (e.g., H1N1, H3N2).
During infection, the body's immune system attacks the virus and becomes trained to fight the exact same virus more aggressively. However, the influenza virus mutates frequently. As the virus reproduces, the content of the RNA can change slightly, which in turn alters the surface proteins. The immune system does not recognize this new viral strain because it does not possess the exact same proteins already recognized by the immune system from the previous infection.
Symptoms
The clinical presentation can vary in the symptoms that occur and their severity. Most commonly, the flu causes fever, weakness, fatigue, muscle aches (myalgias), headache, sore throat, and running nose. Cough is also a symptom if the infection reaches the lower respiratory tract. Infection of the brain (encephalitis) is an uncommon feature of the flu. Children with influenza can sometimes present with nausea, vomiting, diarrhea, and abdominal pain.
A physician can diagnose the flu based on the symptoms. However, a nasopharyngeal swab can be taken and sent for viral culture if it is necessary for confirmation.
Prevention
The influenza vaccine is administered in the fall in preparation for the winter months. It usually contains components of two strains of influenza A and one strain of influenza B. Because of how often the virus mutates, the contents of the vaccine change every year to protect against the viral strains most likely to cause infection in the upcoming winter months. Individuals who should have the vaccine include those who are more than 65 years of age, have cardiopulmonary disorders, have diabetes mellitus, live at chronic care facilities, and work in health care. Children on long-term aspirin and pregnant women expected to be in the second or third trimester in the winter months should also receive the vaccine.
Even if influenza occurs, it is self-limiting most of the time. There are antiviral medications for the flu, including oseltamivir (Tamiflu) and zanamivir (Relenza). Amantadine and rimantadine are also treatment options, but there is increasing resistance to these medications.
