Newsletter Highlight :

By Dr CM Tam, Consultant of Chest Services , Department of Health, Hong Kong.

(The HKEA Newsletter 2000, 1(3), p.2. )

CONTROL OF TUBERCULOSIS IN HONG KONG

In Hong Kong, there has been an overall decrease in the notification rate of TB in the past 4 to 5 decades, from the peak of 697.2 per 100,000 population in 1952. However, in the past decade, the rate has remained rather stagnant, being at around 110 per 100,000 in recent years. A similar phenomenon of stagnant trend of TB notification has also been seen in some neighbouring countries such as Singapore, Japan, and Malaysia.

The contribution to such a stagnant trend is probably multifactorial. Factors which affect the apparent change in notification rate include notification behaviour, diagnostic practice, and case finding activities. Factors which affect the real change in notification rate include those which affect the 3 components of the TB transmission model: source, vehicle, and host. Sources are infectious TB patients, while vehicles are infectious air droplets. Hosts are the population at risk.

Measures employed in the control of TB will be directed against those 3 components of the transmission model. Hence, measures targeted at the source include good personal hygiene, case finding and effective treatment. For the vehicle, adequate ventilation and isolation of infectious sources are the relevant measures. As regards host, measures include BCG vaccination, preventive treatment, and maintenance of good bodily health of the general population. Among the various measures for TB control, DOTS (directly observed treatment, short course) targeting at the source is the most important one to have the greatest impact. In Hong Kong, DOT has been used in the government chest clinics since the 1970s.

There are various obstacles to TB control in Hong Kong. These include overcrowding, busy
population movement, ageing population, prolonged survival of patients with chronic medical illnesses, and large pool of already infected individuals. Moreover, the stigma attached to TB may adversely affect case finding and case holding. The treatment defaulter rate is at around 8% and this remains an important problem. At present the rate of drug resistance is kept at a relatively low level, and this is attributed mainly to the continuous use of DOT. HIV infection, although not a significant problem on TB control at present, should not be overlooked as this potential problem can escalate very quickly if it is not kept under good control.

The control of TB is a long term work. The collaboration of all health sectors as well as international parties are required.
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