Health Education

Seasonal influenza, better known as the flu, is caused by influenza viruses that infect the respiratory tract. The viruses spread from person-to-person by droplets coughed or sneezed in the air or direct contact. In Hong Kong, there are two flu seasons: from January to March and July to August, during which more people get the flu.

How do I know if I have a cold or the flu?

You might have the flu if you have the following symptoms:

• Fever (100 F or 37.8^oC and higher; often higher in children)
• Chills
• Runny nose or sneezing
• Cough
• Sore throat
• Muscle aches
• Headache
• Dizziness  
• Fatigue
• Loss of appetite
• Sometimes diarrhoea and vomiting

Sometimes, it is not easy to tell because common cold and flu share many symptoms, although flu symptoms tend to be more severe. Some doctors may perform rapid tests on patient’s respiratory secretions to confirm the diagnosis.

Who are at risk of flu-related complications? 

Most people with the flu have mild symptoms and they usually get better within a week. However, some people can become very sick and develop complications. People who are at high risk of developing flu-related complications include:

• Young children
• Seniors aged 65 or older
• Pregnant women
• Patient with asthma or chronic obstructive pulmonary disease
• Patients with other medical conditions, such as diabetes, kidney, or liver disease
• Patients with a weak immune system

What are the serious complications of the flu?

Flu-related complications, although not common, occur from time-to-time. These complications include:

• Pneumonia
• Worsening respiratory symptoms for those with asthma or chronic obstructive pulmonary disease
• Secondary bacterial infection
• Febrile seizure in young children
• Rare but life-threatening complications: inflammation of the heart muscle (myocarditis), inflammation of the brain tissue (encephalitis), inflammation of the peripheral nerves (Guillain-Barre syndrome)

What are the warning signs that you need to see a doctor right away?

In children

• Having trouble in breathing or breathing fast
• Bluish lips
• Not waking up or playing
• Not eating or drinking
• Becoming irritable
• Producing no tears when crying
• Having fewer wet diapers than usual
• Seizure
• Skin rash
• Worsening symptoms

In adults

• Shortness of breath or difficulty in breathing
• Chest pain
• Confusion
• Severe or persistent vomiting
• Worsening symptoms

Do I need to take antiviral medication or antibiotics?

Most patients do not need to take antiviral medication. What you need to do is to stay home, take adequate rest, drink plenty of water, avoid spreading the viruses to other people by washing your hands frequently and covering your nose and mouth when cough or sneezing. Your doctor may prescribe medication to relieve your flu symptoms.

Antiviral medicines may be prescribed to those at high-risk of developing flu-related complications. These medicines work best when used in the first 48 hours of flu-like symptoms.

Antibiotics are not useful in viral infection unless there is evidence of secondary bacterial infection.

What can I do to protect myself and my family?

Prevention is always better than cure. The best way to protect yourself against the flu is to get a flu vaccination every year. A healthy life-style and good personal hygiene are also important.