In late March and early April 2009, the outbreak of the novel Influenza A H1N1 virus infection was first detected in Mexico. This virus subsequently caused the 2009 H1N1 flu pandemic. A pandemic is said to occur if a new virus emerges and spreads around the world. In Malaysia more than 15,000 individuals were confirmed to have been infected with this virus during the initial wave of the pandemic.

Symptoms and signs

Symptoms of infection with the flu virus are similar to those of seasonal flu, including:

  • Fever (temperature higher than 37.8ºC) and chills
  • Cough
  • Sore throat
  • Body aches or headache
  • Fatigue
  • Vomiting and diarrhea (not typical with seasonal flu)


Complications of influenza occur in some people; pneumonia is the most common complication. Pneumonia is a serious infection of the lungs and is more likely to occur in

  • pregnant women;
  • infants, and young children particularly under age 2;
  • people of any age with certain chronic health conditions (including asthma or lung disease, heart disease, diabetes, kidney disease or some neurological conditions);
  • people with severely compromised immune systems eg : those infected with HIV, those on longterm steroids, cancer treatment, etc.


Most people will recover with simple home remedies. Take good rest and take plenty of fluids. Use paracetamol if you have aches and pains. However you should see a doctor if

  • You feel short of breath or have trouble breathing
  • You have pain or pressure in your chest or stomach
  • You have signs of being dehydrated, such as dizziness when standing or not passing urine
  • You feel confused
  • You cannot stop vomiting or you cannot drink enough fluids
  • Your fever continues for more than 2 days

In children, you should seek help if the child has any of the above or if the child:

  • Has blue or purplish skin color
  • Is so irritable that he or she does not want to be held
  • Does not have tears when crying (in infants)
  • Does not wake up easily

Antiviral medicines such as oseltamivir (Tamiflu®) and zanamivir (Relenza®) work best if taken within 48 hours. Let your doctor decide whether you will need any of these medications

You also need to prevent spreading this virus to people around you. You can spread the infection one day before you have symptoms until at least 24 hours after your fever has gone (without taking anti-fever medicines). Children and people with a weakened immune system may be contagious for more than seven days. So when you are unwell,

  • Stay at home and keep aways from work, school or crowds.
  • Cover your coughs and sneezes. If you are using tissues, make sure you dispose of them carefully. Clean your hands immediately after with soap and water or cleanse them with an alcohol-based hand rub
  • If you do not have a tissue close by when you cough or sneeze, cover your mouth as much as possible with the crook of your elbow, see picture;
  • You can also use a mask to help you contain the spread of droplets when you are around others;
  • Inform family and friends about your illness and try to avoid contact with other people;


The way H1N1 influenza A virus spreads from one person to another is similar to other flu viruses. The virus can be spread by coughing or sneezing, or by touching surfaces contaminated with the virus and then touching your nose or mouth. We can prevent ourselves from getting infected by

  • Keeping our distance from people who show symptoms of influenza-like illness, such as coughing and sneezing (trying to maintain a distance of about 1 meter if possible);
  • Clean hands thoroughly with soap and water, or cleanse them with an alcohol-based hand rub on a regular basis (especially if touching surfaces that are likely to be contaminated);
  • Avoid touching your mouth, nose and eyes as much as possible;
  • Reduce the time spent in crowded settings if possible;
  • Improve airflow in your living space by opening windows;
  • Practice good health habits (including adequate sleep, eating nutritious food, and keeping physically active); and

Getting vaccinated with the standard trivalent seasonal influenza vaccines.

Last reviewed : 28 August 2020
Writer : Dr. Suresh Kumar a/l Chindambaram
Reviewer : Dr. Nor Faizah bt. Ghazali