Travel Health Service Influenza
Travel related diseases


What is influenza?

Influenza is a very contagious respiratory infection caused by flu viruses. The flu viruses are divided into three types, designated A, B, and C. Currently, three different influenza strains circulate worldwide: two type A viruses (commonly H3N2 and H1N1) and one type B. "H" and "N" are the abbreviations of the proteins of the virus and are used for classification of the viruses. The incubation period is 1-3 days. Clinically, people may present with fever, headache, chills, malaise, muscle aches, dry cough, sore throat, running nose, or diarrhoea. Usually, people will recover completely in 1-2 weeks. However, the disease may exacerbate any underlying medical condition such as lung or heart diseases and cause serious and potentially life-threatening medical complications, e.g. bacterial pneumonia, primary influenza viral pneumonia or even death.

Influenza virus
Influenza virus
(Acknowledgement: Public Health Laboratory Services Branch, Centre for Health Protection )

How does it spread?

The virus is transmitted mainly through airborne respiratory droplets. Spread by direct contact is also possible.

How can it be prevented?

Influenza can be prevented through a healthy lifestyle. Avoid smoking. Have adequate rest, a balanced diet, regular exercises and make efforts to minimize stress. Avoid crowded places during the flu season. Avoid direct contact with infected persons. Beware of indirect contact also, e.g. using the same glass as a patient.

The disease can also be prevented through influenza vaccination, especially for those who are at high risks of developing complications, e.g. the elderly, those with heart and lung diseases.

How is it treated?

Treatment aims at symptomatic relief. Drugs such as paracetamol, anti-cough syrup, sputum softening mixture, cold tablet and lozenges are used commonly for treatment. Patients are advised to drink plenty of water, at least 8 glasses a day. Rest will allow your body to use its own defence to fight the virus. Antiviral drugs such as amantadine and rimantadine are sometimes used under medical supervision.