Influenza is a respiratory illness which is highly contagious. Learn more about the symptoms and the influenza vaccine.

Stay a step ahead of the flu with a flu shot.

Those who are at risk of serious flu complications like older people, young children and people with certain chronic conditions should get vaccinated. The best way to prevent the flu is by getting a flu vaccine or flu shot each year.

Influenza, commonly known as the "flu", is a contagious disease that can affect anyone, including healthy people. It attacks the respiratory tract in humans (nose, throat, and lungs), causing inflammation of the mucous membranes.

It can be spread when an infected person coughs, sneezes, or speaks. The flu viruses are transmitted into the air through droplets, and other people breathe in the viruses. When these viruses enter the nose, throat, or lungs of a person, they begin to multiply, causing influenza symptoms. The viruses can also be spread indirectly when a person touches a surface with flu viruses on it (for example, a doorknob) and then touches his or her nose or mouth. Transmission can also occur when an infected person shares food with others during mealtime without a serving spoon.

  • Flu is usually a more severe condition than the common cold.
  • The disease can be deadly to some people who develop life-threatening complications like pneumonia.

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Causes & Risk Factors

Influenza is caused by the flu virus which has 3 main types: flu A, flu B and flu C. Flu A and B are responsible for seasonal outbreaks and epidemics. Between the two types, flu A causes more severe cases and complications like pneumonia, especially in the elderly, the very young (5 years and below) and those with chronic conditions.

Influenza Symptoms and Signs

Flu symptoms usually come suddenly, which include high fever, sore throat, coughing, headache, muscle aches, and stuffy nose.

Other symptoms may include sneezing, nasal discharge, loss of appetite, fatigue, weakness, chills, and stomach symptoms.


A severe case of influenza can lead to pneumonia and other complications such as bronchitis, sinusitis, ear infection and meningitis (inflammation of the lining that covers the brain).

Who is more likely to develop complications from an influenza infection?

Persons who get the flu virus may have different reactions to the illness. Some groups of people are at high risk to develop complications which could lead to death. Older people, young children, people with a weakened immune system, or those with heart and lung diseases are more likely to develop serious complications due to an attack of flu.

The following are the groups at risk for complications related to influenza infection.

  • Persons aged 65 years and older;
  • Children who are 6 months to under 5 years old;
  • Adults and children who have chronic disorders of the lungs (including asthma) or heart;
  • Adults and children who suffer from chronic metabolic diseases (including diabetes); people with kidney malfunction like those on dialysis; those with a blood disorder like thalassemia;
  • People whose immune resistance is lowered due to medications or those whose immune system is weakened due to the Human Immunodeficiency Virus (HIV) infection;
  • Children and teenagers aged 6 months to 18 years who are receiving long-term aspirin therapy (they are at risk of Reye syndrome, which is a deadly disease that affects all body organs especially the liver and brain, after influenza infection);
  • Women who are in the second or third trimester of pregnancy.

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There are antiviral medications available to treat the flu. These medications act to decrease the ability of flu viruses to reproduce. To be effective, flu antiviral drugs should be taken within the first 2 days after the person gets sick. They may also help reduce the severity of flu symptoms and help the person with flu recover faster by a few days. It is important to remember that these flu antiviral medications are not a substitute for flu vaccination. Getting a flu vaccine yearly is still the best way to protect you from the flu.


High fever and a sore throat are influenza symptoms

People who develop influenza symptoms should seek medical attention promptly. Strenuous physical activities like running and jogging should be avoided during the illness until complete recovery. They are advised not to go to work or school and avoid crowded places to minimise the transmission of the infection to others.


There are many ways to prevent the spread of flu and to protect yourself against this infection. Assess the situation you are in. Do you belong to the group at risk of developing influenza-related complications? Are you regularly exposed to those at risk of complications from flu? A flu vaccine may be warranted and is the best protection for you against the flu.

Where flu vaccine availability is limited, vaccination is not required for the general population. However, everyone can practise healthy habits, good personal hygiene and be socially responsible.

Wash your hands thoroughly and regularly with soap and water, especially before touching your eyes, nose or mouth and after going to the toilet.

  • Cover your mouth and nose with a tissue when coughing or sneezing
  • Wear a surgical mask if you are unwell
  • See a doctor if you are feeling unwell
  • Do not go to school or work when you are ill
  • Never spit in public places
  • When sharing food at meal times, use a serving spoon

Lead a healthy lifestyle

  • Eat a balanced diet, including plenty of fruits and vegetables
  • Do 30 minutes of physical activity at least 5 days a week
  • Have enough sleep and rest. Keep stress levels low
  • Do not smoke

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Flu Vaccination

Influenza vaccination, or flu vaccination for short, is most beneficial for those who have a high chance of developing complications (see list above) from an influenza infection. Unless advised otherwise by your doctor, it is recommended that you go for flu vaccination even if you are healthy, especially if you live with or take care of the following people:

  • The elderly (aged 65 years and above)
  • People with low immunity (e.g. under cancer treatment or have certain diseases like HIV)
  • Children aged 5 years and below

It is also advisable to get a flu vaccination if you are a healthcare worker as you may regularly be exposed to different flu viruses. You will also be protecting your patients by preventing the spread of the virus to them.

The flu vaccination takes effect in about 2 weeks, thus it’s better to get vaccinated early before flu season starts. In Singapore, the flu season generally occurs between December and February. Another peak season is from May to July.

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Flu vaccines are offered in many locations, including hospitals, polyclinics, GP clinics and even schools. 

Some minor side effects can be associated with a flu vaccination. They are:

  • Soreness, redness, or swelling where the shot was given
  • Muscle aches
  • Runny nose
  • Headache
  • Fever (low grade)
  • Cough
  • Sore throat
  • Vomiting (more likely to happen to children)

If these problems occur, they begin soon after the shot and usually lasts 1 to 2 days. However, on rare occasions, flu vaccination can cause serious problems, such as severe allergic reactions. As not everyone is suitable for a flu vaccine, you should consult your doctor before getting vaccinated.

Yearly vaccination is recommended as flu viruses are constantly changing, and your body’s immunity to influenza viruses may decline over time. Thus, getting vaccinated every year provides the best protection against influenza.

*Note: This flu vaccine does not give protection against bird flu or the H7N9. Currently, there is no vaccine for this strain.

Use of Medisave

MediSave can be used up to $500/$700 per year per account can be used for influenza vaccinations for persons with a higher risk of developing influenza-related complications.

Click here for more information on subsidies available, other vaccine-preventable diseases and frequently asked questions.

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