[Influenza--always present among us].Med Pregl. 2000 Mar-Apr; 53(3-4):154-8.MP
Influenza virus infects about 10 million persons worldwide each year. Two important characteristics of influenza are its epidemic outbreak and high mortality rate, mostly caused by complications. Influenza virus is characterised by a great antigenic variability. Major modifications, called antigenic shifts or type changes, occur approximately three times per century and result in worldwide epidemics--pandemics. Minor modifications, called antigenic drifts or strain changes demand new vaccine compositions each year.
Pandemics and epidemics caused by influenza virus, such as the "Spanish Flu", the "Asian Flu", the "Hong Kong Flu" killed many people worldwide. Presently the epidemic, caused by influenza A virus Sydney/97 H3N2 is spreading over USA and most of Europe, including Yugoslavia. EPIDEMIOLOGY AND CLINICAL FEATURES: In humans influenza virus spreads over respiratory secretions, thrown out by coughing and sneezing. Children and older people, as well as immunosuppressed patients are prone to the infection. The onset of illness is sudden, with fever usually over 39 degrees C. Headache and myalgia are prominent. Other signs include fatigue, sore throat, nasal congestion and red eyes. Cough is a very important symptom, which starts as dry and progresses to wet with thick mucous.
Pneumonia is the main cause of death among the high-risk patients. Bronchitis and tracheobronchitis also occur. Croup is a serious complication, often encountered in small children. Cardiac complications, especially myocarditis, are described as influenza complications. Neurological complications include encephalitis, encephalopathy, myelitis, Guillain-Barré syndrome, Reye syndrome, etc. Neurotropism of the influenza virus is under investigation. DIFFERENTIAL DIAGNOSIS AND DIAGNOSIS: Differential diagnosis of influenza includes all diseases which exhibit by increased body temperature, cough, headache, sore throat, myalgia and lethargy. Among serious diseases, pneumonia, sepsis, and meningitis should be considered. Various tests are used when diagnosing influenza: antigen detection, polymerase chain reaction, immunofluorescent tests, etc.
Treatment of influenza by antiviral drugs can be prophylactic and therapeutic. Amantadine and rimantadine are older drugs effective in cases caused by virus type A. The newest generation of influenza antiviral agents are neuraminidase inhibitors--zanamivir and oseltamivir, effective against both virus types. The symptomatic therapy is still a basis of influenza treatment.
The main means of influenza prevention is a yearly vaccine. The three-valent vaccine is in common use. It is recommended that high-risk population should be vaccinated. If the composition of the vaccine is well matched with the prevalent virus strain, it is efficient in 50-80% of vaccinees.
Influenza is the sixth cause of death in the world, the forth among the older population. The next pandemic can occur at anytime. It will be a different virus subtype, never before encountered by humans. Are we ready?