A study is based on records from 1979 to 2001 from about 500 hospitals across the United States concluded that, on average, more than 200,000 people are hospitalized each year for respiratory and heart conditions associated with influenza virus infections in both previously healthy persons and those with prior underlying conditions. In Austria, in 1990, a total of 3,808 patients with influenza were hospitalized for treatment (49/100,000). In this group the age-specific incidence rates showed three peaks: < 5 years (132/100,000), adolescents (15 to 19-year-olds, 112/100,000), old-age groups (85-year-olds, 103/100,000). Complications occurred in 1,479 (38.8%) of patients.
Young children may suffer middle ear infection (30% to 45%), gastrointestinal discomfort or croup. They can also have initial symptoms mimicking bacterial blood poisoning with high fevers, and up to 20% of children hospitalized with influenza can have seizures caused by fever.
Usually the most serious consequences are seen to increase with age, particularly above about 65 years. The body needs to be strong to battle the influenza virus. For people with weaker health such as aging people, diabetics or people with heart disease, an attack of influenza may ask too much strength and energy. In these persons, influenza can be lethal. During influenza epidemics the attack rate of influenza can be as high as 60-75%% in certain closed communities such as nursing homes, with a mortality rate sometimes exceeding 30%.
1. The lungs
Influenza complications usually arise from bacterial infections of the lower respiratory tract. Croup, exacerbation of chronic obstructive lung disease (chronic bronchitis, asthma, emphysema and cystic fibrosis), and pneumonia are all seen during influenza infections. The most life-threatening of these is pneumonia. If not resolved, death may result from obstruction of air flow to the lungs, arrhythmias of the heart, blood poisoning and shock characterized by low blood pressure, mental dulling, high fever, vomiting, diarrhea and inflammation of the mucous membranes, Rapid onset of high fever and the progression of cough to severe shortness of breath, and bluish discoloration of skin and lips are consistent with a diagnosis of severe influenza virus pneumonia. Lack of response to therapy for lung edema and heart failure due to accumulation of an excessive volume of blood in the heart may occur in persons with underlying heart disease. There are three types of complicating pneumonia:
Bacterial pneumonia is the most common and may occur in previously healthy persons after the influenza virus has damaged the surface cell in the airways, as well as in those with underlying disease rendering them more susceptible to bacterial infections. The presence of a bacterial infection should be strongly considered in patients who report a severe fever or the reappearance of fever or other symptoms of bacterial infection in the respiratory tract after their initial influenza illness has improved. Combined viral and bacterial pneumonia is less common, but it may be more common in patients with chronic cardiovascular and lung diseases. It has a case mortality rate of 10-15%. Pure viral pneumonia is rare, but nearly always fatal.
Bronchiolitis is an inflammation of the small air passages (bronchioles). It usually affects children under the age of 2 years. It is the leading cause of serious lower respiratory illness in infants. Symptoms of bronchiolitis include labored, rapid breathing with wheezing and a "tight"-sounding cough. If the infection becomes severe, the infant's breathing rate may increase noticeably. If severe difficulty in breathing occurs, immediate medical attention is needed.
2. The heart
Inflammation of the heart muscle (myocarditis) and the sac around the heart (pericarditis) may occur. The most common cardiac complication is arrhythmia of the heart chambers particularly in older persons, but cardiac complications have also been observed in healthy young adults. It may indicate the presence of a heart disease due to an inadequate blood flow. ECG changes during acute influenza are noted in patients who have a heart disease but these ECG changes are caused by exacerbation of the underlying heart disease rather than by a direct effect of the influenza virus on the heart muscle
3. Inflammation (myositis) and destruction of skeletal muscles
Involvement of muscles has been reported most commonly after influenza B infection of children. Leg pains and muscle tenderness last for 1-5 days. Destruction of the skeletal muscles may result in acute renal failure. Specific treatment may be necessary.
4. Central nervous system
Inflammation of the spinal cord and brain rarely occurs (encephalitis). Mania and schizophrenia were associated with the 1918 influenza pandemic.
5. Reyes syndrome
Reye's syndrome causes fatty accumulation in the organs of the body, especially the liver. This is a rare liver and central nervous system complication seen after viral infections, in particular influenza B, almost exclusively occurring in children, and linked with use of salicylates (aspirin). Symptoms are a change in mental status, nausea and vomiting due to edema of the brain. It may be fatal in up to 40% of cases.
6. Fatigue
Fatigue and a lack of energy that persist after influenza symptoms are gone. People may take several weeks to fully recover, although no cause for the symptoms has been identified.
Thus the potential damage of influenza infections should not be underestimated. For all matters relating to prevention and treatment of influenza, always check with your doctor or other health care provider for professional medical advice.
