Influenza

Influenza, also known as the flu, is an infection caused by influenza viruses. Despite being commonly confused with the common cold which is caused by other respiratory viruses, influenza is usually more severe.

Definition & Characteristics

There are three main types of viruses responsible for influenza infections – Type A, Type B and Type C.

Influenza A and B are associated with annual outbreaks and epidemics. Influenza C is associated with mild sporadic illness and occurs less frequently than Influenza A and B.

How Influenza Spreads

Influenza is spread from person to person through respiratory droplets propelled by coughing and sneezing.

Influenza can also be passed on through contact with contaminated surfaces, for example touching an object like a doorknob or telephone receiver that has been recently handled by someone who is infected with influenza and then touching the nose or mouth.

Adults may be contagious from one day before the onset of symptoms till 5 to 7 days after onset. Children and persons with weakened immune systems may be infectious for longer periods of time.

Symptoms

Influenza is characterised by a sudden onset of symptoms such as:

  • Fever
  • Headache
  • Chills
  • Cough
  • Sore throat
  • Muscle aches
  • General malaise and fatigue

Gastrointestinal symptoms, such as nausea, vomiting or diarrhoea, can sometimes accompany influenza, especially in children, but these symptoms are rarely prominent.

Influenza can result in pneumonia, hospitalisation or even death, especially in populations at higher risk of developing complications of influenza. This includes:

  • Persons aged 65 years and older;
  • Children aged 6 months to less than 5 years (i.e. 59 months);
  • Adults and children who have chronic disorders of the lung  or heart systems, including asthma;
  • Adults and children who have required regular medical follow-up or hospitalisation during the preceding year due to chronic metabolic diseases (including diabetes mellitus), renal, neurologic, liver, or blood disorders, or immunosuppression (including immunosuppression caused by medications or the Human Immunodeficiency Virus);
  • Children and adolescents aged 6 months to 18 years who are receiving long-term aspirin therapy and therefore might be at risk for developing Reye syndrome after influenza infection;
  • Women at all stages of pregnancy;
  • Residents of nursing homes and intermediate and long term care facilities;

What to Do If You Have Influenza

If you suspect you have an influenza infection, you should stay home and avoid contact with other people except to seek medical care. You should also avoid strenuous physical activity such as jogging and running during the illness until complete recovery.

Most people with influenza have mild illness and do not require medical care or antiviral drugs. If you are concerned about your illness, please consult your doctor.

However, people at higher risk of developing complications of influenza should consult their doctor on the need to be examined if they get influenza-like symptoms.

Seek immediate medical attention if you experience the following warning signs:

Adults Children
  • Breathing difficulty
  • Pain or pressure in the chest or abdomen
  • Confusion
  • Persistent vomiting
  • Sudden dizziness
  • Influenza-like symptoms that improve but then return with fever and worse cough
  • Breathing difficulty
  • Bluish skin colour
  • Fever with a rash
  • Not drinking enough fluids
  • Not waking up or not interacting
  • Being so irritable that the child does not want to be held

Treatment of influenza

Antiviral medications are currently available for the treatment of influenza. They can help reduce the severity of symptoms and promote recovery.

To be effective, antivirals should be taken within the first two days of illness. Antivirals can be classified into:

  • adamantanes (eg amantadine and remantadine) and
  • neuraminidase inhibitors (eg oseltamivir and zanamivir)

Precautions You Can Take

Annual influenza vaccination is recommended to protect against influenza, especially for individuals belonging to populations at higher risk of complications of influenza. With effect from 1 Jan 2014, the use of Medisave will be allowed for influenza vaccination for persons at higher risk of developing influenza-related complications.

People living and caring for high-risk individuals should also be vaccinated against influenza. Other measures include:

  • Practising good personal hygiene to prevent the spread of influenza. Wash your hands regularly and thoroughly with soap and water, especially before touching your eyes, nose or mouth
  • Turning quickly away from anyone and cover your nose and mouth with a tissue when coughing and sneezing.
  • Avoiding crowded places if you are unwell.
  • Staying home from work or school when you are sick.
  • Using a serving spoon when sharing food at meal times.

 

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