Otitis media and croup (in children)
As each mother will know, children are prone to middle ear infections (otitis media) with any upper respiratory infections. Croup (a viral infection of the vocal cords and large main airways) is a risk with para-influenza and influenza infections especially.
This form of pneumonia occurs when there is severe lung damage caused by the influenza virus itself. It usually begins early in the illness.
The person will have a worsening cough and become short of breath. In severe cases, the person may have a bluish tinge and become confused due to lack of oxygen.
This form of pneumonia is very serious, will require the person to be supported on a ventilator in hospital, and might be fatal.
Bacterial bronchitis and pneumonia
This occurs when bacteria causes a secondary infection in the lungs. It is far more common than the pure viral pneumonia mentioned above. It often occurs a few days after the worst influenza symptoms are over, thus appearing to be a "relapse".
Fever reappears along with a cough that produces sputum. Usually one of the following bacteria (Pneumococcus, Staphylococcus, Streptococcus, or Haemophilus influenzae type B) is responsible, and can be treated with an antibiotic.
Some doctors recommend people in high risk groups to be vaccinated against pneumococcal pneumonia as well as influenza.
Myositis and myocarditis
Rarely, inflammation of the muscles of the body (myositis) can occur in influenza. This will be evident with painful tender leg muscles, most often in children.
Also, very rarely, inflammation of the heart muscle (myocarditis) can occur. Symptoms include tiredness, shortness of breath, heart palpitations, a rapid pulse, and discomfort in the chest.
Because myositis and myocarditis might be more likely to happen if the muscles are put under stress, it is not advisable to exercise while ill with influenza (or any viral illness).
Complications of the nervous system and brain
In young children, febrile convulsions are possible with influenza, as in any illness involving a high temperature.
Although the cause of Reye's syndrome is unknown, it is often associated with the influenza or chickenpox viruses, in children up to the age of 15-18 years who ingest aspirin. Taking aspirin during an influenza or chickenpox illness may increase the risk of developing Reye's syndrome by as much as 35-fold.
Thus aspirin, and any medication containing aspirin, should not be given to children with fever. White willow bark is a natural aspirin so avoid this.
Reye's syndrome is a very serious condition affecting the brain and liver. The majority of children will recover from Reye's syndrome, but in some cases permanent brain damage and death might follow.
The first symptoms are usually drowsiness and inactivity.
Other types of brain and nervous system disorders can very occasionally follow influenza, such as Guillain-Barre syndrome (a type of paralysis) and encephalopathy (brain dysfunction).
Reviewed (2006) by Dr Jane Yeats MBChB, BSc(Med)(Hons)Biochem, FCPathSA(Virology).