It happens Worldwide. In temperate regions, influenza is seasonal disease occurring in winter. It affects the Northern hemisphere from November to March and the Southern hemisphere from April to September.

In Tropical areas there is no clear seasonal pattern, and influenza may occur at any time of the year.

Causative agent:

Influenza viruses of types A, B and C; type A occurs in two subtypes (H1N1 and H3N2).

Type A viruses cause most of the widespread influenza epidemics;

Type B viruses generally cause regional outbreaks, and

Type C is of minor significance for humans.

Influenza viruses evolve rapidly, changing their antigenic characteristics, so that vaccines need to be modified each year to be effective against currently circulating influenza strains.

Other types and subtypes of influenza viruses occur in animals and birds; transmission and reassortment between species may give rise to new subtypes able to infect humans.

Transmission: Airborne transmission occurs particularly in crowded enclosed spaces. Transmission also occurs by direct contact with droplets disseminated by unprotected coughs and sneezes and contamination of the hands.

Incubation period: Usually 1 – 3 days

Sign & Symptoms

Ranging from asymptomatic infection to fatal disease.

Initial symptoms include fever with rapid onset, sore throat, cough and chills, often accompanied by headache, coryza, myalgia and prostration.

llness tends to be most severe in the elderly and in young children. Death resulting from influenza occurs mainly in the elderly and individuals with pre-existing chronic diseases.


Pneumonia and death


Symptomatic treatment

  • Drink warm water and fluids to relieve sore throat and cough.
  • Maintain a balanced diet and sufficient sleep/rest.
  • Avoid stress as it can weaken the body’s immune system.
  • If needed or signs and symptoms persist or worsen, get treatment from clinics or hospitals.

NO Specific treatment

for Influenza Amantadine or rimantadine started within 48hours of onset of Influenza A illness and given approximately 3-5 days. You are advised to consult your doctor for treatment.

Prevention & Precautions

Vaccination as Prophylaxis Annual influenza immunisation is recommended (vaccine strains are continually updated to reflect ongoing antigenic changes among circulating influenza viruses). For most people, influenza vaccine prevents serious influenza-related illness. Will not prevent influenza-like illnesses caused by other viruses. Takes two weeks for protection to develop after immunisation and last up to a year.

Type of Vaccine: Inactivated non-infectious viral

Number of doses: One, given i.m. for individuals > 9 years of age, two doses at least 4 weeks apart for children aged 6 months – 9 years. Half dose to children 6 – 36 months of age.

Booster: Annual; immunocompromised individuals should receive a second dose 4 weeks after the first

Contraindications: Hypersensitivity to previous dose or severe hypersensitivity to egg

Adverse reactions: Local pain and tenderness at injection site (20%), fever, malaise

Before departure: 2 weeks Recommended: High risk groups before the Influenza season, and optional for travelers to countries currently in Influenza season

Special precautions for vaccine: None


Whenever possible, avoid crowded enclosed spaces and close contact with people suffering from acute respiratory infections

Cover mouth and nose with a tissue or handkerchief when sneezing or coughing

Wash hands with soap after coughing/sneezing or touching a contaminated surface

Wear a mask while infected with influenza

A void being in public places when having a cold or influenza.

Last Reviewed : 26 April 2012
Writer : Dr. Norhayati Rusli
Reviewed : Dr. Norhaya Mohd Razali