Colds and flu
The runny nose, sore throat or 'bunged up' feeling of a cold is caused by one of many viruses that infect the upper part of the breathing system (upper respiratory tract). Although a cold can make you feel miserable, in most people they are 'self limiting'. This means the body fights off the infection and cure comes without the need for specific medical treatment.

Influenza - or flu - causes similar symptoms to a cold but tends to be a more severe illness. Although it is also self-limiting in most people, flu can be dangerous for people who are frail or have a weakened immune system.

Generally, there are two peaks for influenza occurrence in Hong Kong - one in February and the other in July, but this can be influenced by imported cases of flu from other countries. In the UK and North America, for example, most flu cases occur between December to March.
How do you catch a cold
The viruses responsible for colds are spread from person to person as droplets in the air from sneezing or coughing, or from touching infected surfaces then transmitting the viruses from the hands to the mouth. Handshakes or touching a door handle are possible routes for transmission of cold viruses.

Infected people can spread the viruses from two days before the illness and up to four days after the symptoms start. Colds can occur all year round but are more common in the winter months. On average, adults catch two to three colds each year. School age children can have up to twelve or more colds in a year.
  • Colds - the virus multiplies in the soft, warm surfaces found in the nose, throat, sinuses, the windpipe (trachea) and the breathing tubes (the bronchi). The main symptoms are blocked or runny nose, sneezing, sore throat and cough. There may also be a fever, aching muscles and fatigue. The symptoms usually last for a week
  • Flu - These are the same as colds but the muscle aching is usually more severe and the fatigue may last for a few weeks after the illness has cleared up

To most healthy adults, flu can be just like a nasty cold. However, young children, the elderly and people with certain chronic medical conditions are susceptible to potentially serious complications. These are mostly related to a 'secondary' bacterial infection of the lungs (pneumonia) or of the ears, nose and throat. In children under about six years old, fits - known as febrile convulsions - can occur as a result of the high body temperature. People living in residential or nursing homes, and people with the following conditions are at risk:
  • Asthma
  • Chronic chest problems such as chronic bronchitis and emphysema
  • Diabetes
  • Heart disease
  • Kidney diseases and kidney failure
  • People with reduced immunity, such as people with HIV or people who have had their spleen removed
There is no cure for colds or flu. Antibiotics, which do work to kill bacteria, do not work on viruses. However, home treatment can help to relieve the symptoms and ensure a speedy recovery.
  • Drink plenty of fluids to prevent dehydration
  • For adults, paracetamol, aspirin or ibuprofen can help to relieve fever and pain. Always follow the instructions carefully and take care not stay within the safe daily doses. It is easy to accidentally exceed these by using more than one product (tablets, capsules, a hot lemon drinkˇK) containing the same active ingredient such as paracetamol
  • For children under 12 years old aspirin can be dangerous (in rare cases, it can cause Reye's syndrome). It should also be avoided in older children and adolescents. Children's formulations of paracetamol (eg Calpol) and ibuprofen (Nurofen Junior) are available
  • Avoid tobacco smoke
  • Decongestants such as pseudo-ephedrine may clear congestion. Ask your pharmacist for advice on products that contain a decongestant
  • Steam inhalations with menthol or eucalyptus, or herbal products such as camomile, may help. Take care with the hot water
  • Eating a balanced diet with plenty of fruit and vegetables is sensible. Vitamin C is often claimed to help, but there is no firm evidence for this
  • Rest. Avoid strenuous exercise, as this can increase the chance of catching a secondary bacterial infection. Contrary to the advertising claims for some cold and flu medicines, if you are unwell with a heavy cold and, especially, flu, carrying on as normal is not advisable
Antiviral medicines
For people in general good health, who are not elderly, no specific medical treatment - apart from the home care suggested above - is required for flu. For vulnerable groups, where it is important to prevent complications or spread, prescription only medicines may be required.
  • There are several anti-viral treatments, taken as tablets or as an inhaler (similar to the ones used for asthma). They have been shown to reduce the duration of flu but only by around one day, and then only if treatment is started within two days of the onset of the illness. GPs are not currently routinely prescribing antiviral medicines for flu
  • Antibiotics may be given to treat any bacterial infections such as a chest infection, ear infection or sinusitis
  • Isolation of people with colds and flu to prevent it spreading to other people, if practical
  • Regular hand washing and immediate disposal of tissues
  • Aim for a healthy lifestyle a balanced diet, rich in fruit and vegetables, and regular (preferably daily) physical activity
  • Do not smoke - smokers are more likely to catch a cold
Having a flu jab each year significantly reduces the chance of catching the illnesses. It is recommended for people at risk from the complications of flu and for everyone over 65.
When to call the doctor
If the following symptoms develop with a cold, you should consult a doctor promptly:
  • Severe vomiting or diarrhoea
  • Earache
  • Difficulty breathing
  • Skin rash
  • Uncontrollable cough
  • Cough with green sputum - phlegm
  • Extreme lethargy or drowsiness
Further information
Pharmacists can give advice on over-the-counter cold and flu remedies.

World Health Organization

National Center for Infectious Diseases
Healthwise (Health Information Resource Centre)
Tel : (852) 2849 2400
Fax : (852) 2849 2900
Email :
Homepage :

This leaflet is for information only. For a detailed opinion or personal advice, please consult with your own doctor
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