FAQ
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| Influenza |
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What is influenza?
Influenza is a highly contagious viral disease. It is caused by various types of influenza virus strains. In Hong Kong, the disease is more common in periods from January to March and from July to August.
Three types of influenza viruses are recognised: A, B and C. Influenza A viruses are further categorised into subtypes on the basis of two surfaces antigens: haemagglutinin (H) and neuraminidase (N).
Infection caused by influenza A viruses is more common. In Hong Kong, the two subtypes of influenza A, H1N1 and H3N2, are more prevalent. New subtype variants appear from time to time and at irregular intervals. This is responsible for seasonal outbreaks and makes periodic reformulation of the influenza vaccine necessary.
What are the symptoms of influenza and its transmission route?
Influenza is an acute illness of the respiratory tract, characterised by fever, headache, muscle ache, runny nose, cough and sore throat. The incubation period for influenza is usually about 1-3 days.
The disease spreads from person to person by respiratory droplets generated by coughing and sneezing. Occasionally a person may become infected by touching objects carrying the virus on the surface and then transferring it to their mouth or nose.
What are the characteristics of influenza viruses?
The surface antigens of influenza viruses undergo frequent changes. Such changes can be minor (called antigenic drift) or major (called antigenic shift).
The greater the difference is between the new influenza viral strain and the previous ones, the less immunity a population will have to it. A person's immunity can reduce the likelihood of infection and the severity of disease if infection occurs.
How does seasonal influenza arise and what is its health risk?
Antigenic drifts (minor changes) of influenza viruses lead to the emergence of new viral strains every year. These minor changes cause seasonal influenza and explain why reformulation of the influenza vaccine is required every year.
For healthy individuals, seasonal influenza is usually self-limiting with recovery in two to seven days.
What is the relationship between seasonal influenza and influenza pandemic?
The occurrence of influenza pandemic results from the emergence of a pandemic strain, which appears when antigenic shift (major change) occurs in the surface antigens of the influenza viruses. The population will have very little or no immunity to the virus, which facilitates the virus to spread more rapidly and extensively than a seasonal influenza virus would.
Influenza pandemic occurs roughly every 10 to 50 years and may strike any time of the year. It is usually associated with a great number of cases, higher severity of illness, a higher death toll and consequently greater social and economic disruption.
What measures should I take to prevent from contracting seasonal influenza?
As Hong Kong moves into the seasonal flu peak season, you should take steps to further fortify your health. Influenza vaccination is an effective means for the prevention of influenza and its complications, and is recommended for the elderly and patients with chronic diseases. Observing good personal and environmental hygiene, frequent handwashing, maintaining good ventilation, avoiding crowded places if one is feeling unwell and developing good body resistance through adopting a healthy lifestyle with regular exercise and a balanced diet, are ways to prevent seasonal influenza.
Should I get vaccinated to prevent the seasonal influenza?
Influenza vaccine is effective against seasonal influenza. Usually it is suggested that vaccine should be received in autumn every year. About two weeks after vaccination, our body will develop a sufficient level of antibodies to protect against influenza virus infection. However, influenza vaccine can only provide protection against human influenza but NOT avian influenza.
What should I do if I develop symptoms of influenza?
You should put on a mask and consult a doctor if you develop flu symptoms. Take good care of your body and facilitate speedy recovery by staying home and taking ample rest, consuming adequate amounts of water and nutritious and easily digestible food, and keeping good ventilation.
How do I know that I am not having avian influenza?
The initial symptoms of avian influenza are similar to those of seasonal influenza. However, avian influenza is more likely to result in high fever, chest infection, respiratory failure, multi-organ failure and even death.
Avian influenza is transmitted from infected live birds to humans. Human-to-human transmission is inefficient. Therefore, if you have not come into close contact with infected live poultry or birds or their droppings, there is no need to be unduly worried about acquiring avian flu.
What is the treatment of seasonal influenza?
The mainstay of treatment is to take adequate rest, drink plenty of water, and stop smoking. Consult a doctor if symptoms persist or deteriorate. Medication may be prescribed to relieve symptoms. In some cases, your doctors may choose to use certain antiviral drugs to treat influenza. You should follow the instruction given by doctors. Since influenza is caused by virus but not bacteria, antibiotics are of little value in this situation.
How does Chinese medicine see influenza?
Colds may occur throughout the year but are particularly common in winter and spring. They are mainly manifested as nasal obstruction and discharge, sneezing, coughing, headache, aversion to chill, fever and general malaise. In Chinese medicine, colds are divided into common cold and influenza according to different pathogenic factors. Common cold is mainly caused by marked changes in climate and temperature, a soak in rain, exposure to wind after sweating, abnormal coldness or warmness, etc. Influenza, on the other hand, is caused by invasion of infectious pathogenic factors, which are spread in the air by the sneezes and coughs of an infected person. As influenza is contagious, can cause epidemic, and results in more serious illness than common cold does with the threat of complications, it should be prevented and treated early. The public is advised to consult a Chinese medicine practitioner for any questions regarding their body constitution, diagnosis or recuperation through dietary adjustments. Individuals, in particular the elderly, children, pregnant women and patients with chronic disease, should consult a Chinese medicine practitioner before using Chinese medicines to prevent or treat colds.
It is said that the Chinese herb Radix Isatidis and medicine such as yinqiao san are very effective against flu. Can I use these Chinese medicines to prevent flu?
There are different kinds of colds and the treatment is based on the cause, symptoms and body constitution of the individual. You should consult a Chinese medicine practitioner before using Chinese medicines for prevention and treatment of colds, and refrain from indiscriminate use of such drugs.
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