What is a flu?
A seasonal flu (influenza) is an acute and highly infections disease of the respiratory tract caused by the
flu virus. There are three major flu
virus types: A, B and C. Virus type A is the most
virulent one and can create serious epidemics or
pandemics (epidemic spreading throughout the
world). Type B usually causes only mild diseases and
type C is less common and has hardly an impact on
flu infections in humans.
Flu symptoms may range from the mild symptoms of
a common cold to serious pneumonia. Symptoms
indicating a flu infection are a sudden onset of
symptoms associated with high fever, intense
malaise, exhaustion, intense headache and muscle
pains, cough with chest pain and difficulty in
breathing, soar throat and pink eye (conjunctivitis).
Flu spreads much the same way as a common cold by
droplet infection. The incubation period is two to
three days; the disease lasts for about five to seven
days, sometimes more than three weeks. Intensity
and duration of the disease may weaken the immune
system seriously and thus increase the risk of
secondary bacterial infections. Particularly, elderly
people with underlying diseases (e.g. chronic lung
and heart diseases, metabolic diseases), immunosuppressed
people and children are at high risk from
the disease itself, as well as from possible
complications.
Flu usually occurs throughout the year, but shows
seasonal outbreaks from December to April in the
northern hemisphere.
