Talking about the influenza (or “flu”) might be like carrying coals to Newcastle because it is a well-known disease experienced virtually by every person during his or her life. In young and healthy persons, the disease is rather annoying but not dangerous. However, in the elderly and debilitated people, the influenza can get a fatal course.
The influenza is caused by the influenza virus that belongs among the group of RNA viruses. The virus spreads by droplets exhaled by a sick person. Virus particles attack the upper and lower respiratory tract and multiply in mucosal cells. The viral particle is characterized by two important surface structures. It is the neuraminidase (N) and haemagglutinin (H). These are relevant to the ability of the virus to spread and penetrate into cells and to spread. Different strains of influenza viruses are classified according to these structures, for example we speak about the H5N1 virus.
Surface structures of influenza viruses changes regularly. This allows the virus to evade our immune system and it is the reason why we can fall ill more than once in our lifetime. The immune system is usually able to defeat the influenza virus and protect us from its recurrence but different version of the virus is not recognized and the immune response must begin all over again. These annual changes of surface structures virus are referred to as the antigenic drift.
Once in few years the virus may undergo the so-called genetic shift, which gives rise to a virus that is genetically more different compared to previous years. The immune system of the majority of people is unprepared and that is why the genetic shift is related to large-scale global pandemics. The consequences can be sometimes devastating; the most known pandemic of so-called Spanish flu in 1918 killed tens of millions people worldwide.
The symptoms are individual. Most people complain about general symptoms of infection such as fever, fatigue, muscle pain, joint pain, malaise and overall feeling of discomfort. These general symptoms are accompanied by signs of respiratory tract infection such as sore throat, cough, chest discomfort, etc. The symptoms usually last for one week. In the elderly the infection can have much more serious course including dehydration, high fever, confusion and possibly fatal outcome. The influenza can be complicated by bacterial infection as bacterial microorganisms more easily attack the weakened organism.
Diagnosis is usually based on clinical symptoms, physical examination and exclusion of bacterial pneumonia by a chest X-ray. Viral and bacterial infections can be distinguished from blood test by checking the level of CRP (C-reactive protein). This substance is strongly increased in bacterial infections but only mildly in viral ones.
You can strengthen your immune system so it is more able to handle the influenza virus. This includes plenty of exercise, hardening by cold baths, daily intake of vitamins in fruits and vegetables, enough sleep, etc. Vaccination is another very effective and yet inexpensive way to protect against flu. Since influenza is typical by annual mutations, it is necessary to get a flu vaccine every year to stay protected. The vaccination means lesser chance of getting sick and when that happens, the infection tends to have a milder course.
There is no curative therapy. An old proverb says that untreated influenza lasts a week and treated influenza seven days. However, it is appropriate to treat at least symptomatically to lower the risk of complications including bacterial superinfection and prolonged problems.
Bed rest in calm and warm place is essential until the flu symptoms start to disappear. We should prevent dehydration from excessive sweating and fever by appropriate fluid intake. Fever can be treated by non-steroidal anti-inflammatory drugs. However, it is wise to treat only high fever above 38-39°C. Elevated body temperature is part of a complex defense reaction. It slows the infection spread and stimulates our immune system. It must be noted that drugs containing acetylsalicylic acid should not be given to children as they may cause the fatal Reye's syndrome. Anti-inflammatory drugs only suppress the symptoms and not the disease itself. The person feels better but the infection is still active. Antibiotic therapy is inefficient against influenza virus but antibiotics can be prescribed against bacterial superinfection.