What're the complications of influenza?
In general, the flu is usually self-limited and not serious. Influenza is responsible, however, for 15% to 30% of the excess number of hospitalizations that occur in winter. About 1% of people who contract the flu end up in the hospital and, on average, 20,000 Americans die every year from complications of influenza. Influenza complications usually arise from bacterial infections of the lower respiratory tract.
Influenza may increase the risk for death in people with existing heart, lung, or circulation disorders. In fact, the higher than average number of winter deaths in people with heart disease may be due only to the occurrence of influenza during those months. Influenza can be dangerous to the elderly, especially those who live in residential homes where there is more risk of contracting the virus through contact with others. People with lung and heart diseases are also more likely to develop complications due to an attack of flu. Those at risk are advised to get a yearly vaccination.
Pneumonia is the major serious complication of influenza. It can develop about five days after viral influenza. It is an uncommon event, however, and nearly always occurs in susceptible individuals about five days after onset. This can be viral pneumonia, in which the influenza virus itself spreads into the lungs, or bacterial pneumonia, in which unrelated bacteria (such as pneumococci) attack the person's weakened defenses. In both cases, the person may have a worsened cough, difficulty breathing, persistent or recurring fever, and sometimes bloody sputum. Pneumonia is more common in older people and in people with heart or lung disease. As many as 7% of older people in long-term care facilities who develop influenza have to be hospitalized, and 1 to 4% die. Younger people with chronic illnesses are also at risk of developing severe complications.
Children under 1 years old have a very high risk, not only for pneumonia but also for other complications, including meningitis and encephalitis (inflammations in central nervous system). The risk declines after age one but is still elevated in children aged three to five. It is often difficult to tell whether pneumonia in small children is related to influenza or caused by respiratory syncytial virus (RSV), the major viral cause of infant pneumonia. Experts estimate that about 25% of severe lung infections are due to influenza.
Every year, influenza strikes millions of people worldwide. Influenza epidemics are most serious when they involve a new strain against which most people are not immune. Such so-called pandemics can infect more than one fourth of the world's population within a three-month period.
This (Pseudocolored) negative-stained (false-colored) transmission electron micrograph (TEM) depicts the ultrastructural details of an influenza virus particle, or “virion”. A member of the taxonomic family Orthomyxoviridae, the influenza virus is a single-stranded RNA organism
This media comes from the Centers for Disease Control and Prevention's Public Health Image Library (PHIL), with identification number #10073.
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