Influenza, or the flu, is an acute infection usually involving the upper and lower respiratory tract. Outbreaks of influenza occur each winter and last for three or four months, leading to infection on average in approximately 5 to 20 percent of the population.
Influenza can worsen the symptoms experienced by people who have chronic obstructive pulmonary disease (COPD) or asthma. It can also make a person more prone to a bacterial infection that causes pneumonia, or the flu virus itself can cause pneumonia. Influenza is the only epidemic infectious disease that annually increases the death rate in the United States, killing thousands each year.
What causes the flu? The cause of flu is a viral infection. There are several types of influenza viruses: Influenza A, B, and C can all cause the flu in humans. Influenza A is responsible for most of the outbreaks and causes more severe disease and more deaths than either influenza B or C. Influenza C is rare.
What are the symptoms?The symptoms of the flu are headache, fever, and muscle aches, often accompanied by chills, cough, sore throat, and weakness. These symptoms usually last for about two to five days and then slowly start to improve.
How is the flu diagnosed? The diagnosis of flu depends primarily on whether someones symptoms match those described for the flu and whether an outbreak of the disease is present in the community at the time of diagnosis. Rapid tests are easily perf formed by swabbing the nasopharynx. They are relatively accurate for making the diagnosis and are useful for determining whether the individual has influenza or a different virus.
Who should get a flu shot? The Centers for Disease Control and Prevention (CDC) recommends annual flu shots for everyone age six months and older to prevent flu or at least reduce its symptoms when it occurs. However, some people put themselves at risk for severe illness or death every year when they avoid the flu shot because of misconceptions about the vaccine. They also put others at risk as they can spread influenza.
It is especially important for high-risk individuals to get an annual flu shot. The high-risk group includes people age 65 and older, those with lung diseases (such as COPD or asthma-even if its mild and under control), and people with certain other chronic illnesses, such as heart disease, diabetes, cancer, or HIV infection. There is evidence that suggests high-dose flu vaccines may boost immune response in the elderly.