Review article

Influenza: Clinical Presentation and Complications

Ilija Kuzman ; Klinika za infektivne bolesti ''Dr. Fran Mihaljević''

Abstract

Influenza or flu is an acute respiratory disease caused by influenza viruses. Influenza viruses are continuously changing, and antigen changes of influenza A virus are responsible for epidemics occurring each winter and for pandemics occurring every several decades. The clinical features of influenza primarily include general symptoms, i.e. high temperature and headache, muscle pain and fatigue. Respiratory symptoms, primarily dry cough and sore throat, usually occur after a day or two. Generally, influenza is a serious disease due to a number of complications that may be caused by either influenza virus itself or secondary bacterial infections. The most frequent complications are respiratory complications, especially pneumonias, but other organ systems may be also affected. Pneumonia is a very common, severe and often fatal complication of influenza because it is responsible for the majority of fatal outcomes. Clinically and pathophysiologically, there are two forms of pneumonias in influenza. These are primary viral pneumonia caused by influenza virus, which occurs at the onset of the disease, and secondary bacterial pneumonia, which usually occurs during the second week of the disease. In children, pneumonia occurs much more rarely than in adults. Laryngitis, croup and bronchiolitis have been observed relatively frequently, as well as exacerbation of chronic bronchitis and asthma. Bacterial superinfections with otitis and sinusitis have been also frequently observed. Nervous system is more frequently affected in children than in adults. Neurological complications of influenza include convulsions, encephalopathy, meningitis and encephalitis, Guillain-Barré syndrome, transverse myelitis and Reye’s syndrome. Hepatic impairment has been observed relatively frequently, while myositis, myocarditis and pericarditis have been observed rarely. Rhabdomyolysis with acute renal failure has been recorded in some patients. The clinical features of the disease caused by pandemic virus A (H1N1) are not significantly different from those of seasonal influenza. The most important difference is a higher morbidity and a greater number of complications and fatal outcomes in patients below the age of 55, while in seasonal influenza, the majority of complications and fatal outcomes have been recorded in patients above the age of 65 years. The most frequent complication of pandemic influenza is primary viral pneumonia, often accompanied by acute respiratory distress syndrome (ARDS), while secondary bacterial infections occur rarely.

Keywords

influenza; clinical presentation; complications; pandemic

Hrčak ID:

76432

URI

https://hrcak.srce.hr/76432

Publication date:

3.1.2011.

Article data in other languages: croatian

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