Influenza is an acute respiratory tract infection characterized by fever,
rhinitis, coughing, headaches and malaise. Once contracted, influenza may
aggravate cardiac insufficiency, make diabetic management more difficult, or
aggravate asthma.
The influenza virus is also capable of making the body more susceptible to
secondary bacterial infections, particularly those due to pneumococcus,
staphylococcus or non-group Haemophilus influenzae.
There are a number of influenza viruses: two major types (A and B), group A being divided into 2 sub-types.
The third (type C) is very rare.