Tuberculosis in Hong Kong

William N.K. CHEN
Chief of Service, Respiratory Medical Department, Kowloon Hospital, HKSAR

 

1. Control of Tuberculosis in Hong Kong / Hong Kong SAR - An Overall View

In the 18th century in Europe, Tuberculosis was described as the 'White Plague' as it killed more than a million people a year and most of them were children and young adults. Hong Kong was not exempted. The highest mortality was recorded in 1938. There were 332 deaths for every 100,000 population. Since 1939, the Government also introduced the notification rate for Tuberculosis. After the second world war, the Hong Kong Government has been very active in fighting Tuberculosis by setting up chest clinics in the densely populated residential areas in Hong Kong Island and the southern part of Kowloon Peninsula. TB Sanatoriums/hospitals were set up for inpatient treatment of Tuberculosis. Ruttonjee Sanatorium and the Grantham Hospital were the 2 first TB hospitals founded in Hong Kong for management of Tuberculosis.

Despite the proactive attitude of the HK Government, Tuberculosis was still not under control after the second world war. This was due to the large influx of new immigrants from China, glommy economy and overcrowdiness which favoured the transmission of Tuberculosis. Apart from the high mortality, the notification rate was also astonishing. The highest notification rate recorded was in 1952. For every 100,000 population, 697 new cases of Tuberculosis had been notified. The death rate was still over 200 per 100,000 population (comparing with the present figure, only 5-7 deaths per 100,000 population). One out of 5 deaths were due to Tuberculosis and TB was the first leading cause of death in the early 50's. The average age of death was 25. At that time, a lot of young children and babies died of Tuberclous meningitis. The average age of death due to Tuberculosis is now over 70.


Click for enlarge

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With active intervention done by the Government, the notification rate of Tuberculosis declined rapidly in Hong Kong. I would like to quote some statistics from the Annual Report of the Chest Service of the Medical and Health Department, HK Government, and you would certainly agree with me that Hong Kong did make significant progress in the control of Tuberculosis in the 30 years post war.

Year

TB Notification

Notification Rate per 100,000 Pop

TB death per 100,000 pop

Deaths

-------x 100%

Notification

% of TB Deaths below 5 yrs

% of TB. Deaths below 1 yr.

Infant Mort. Rate from TB per 1,000 Live Births

% of TB Deaths among Total Deaths

Average age of TB Deaths

1951

13,886

689.0

207.9

30.17

34.0

7.70

4.73

20.0

25

1975

8,192

187.6

14.8

7.89

1.39

0.31

0.03

3.0

58.5

In the early 80's, the rate was less than 150 per 100,000 population. The results were very encouraging. Active joint research work between the chest service of HK Government and the TB and Chest Unit of the Medical Research Council, UK had been started since the late 60's. The results were published in world renowned journal such as the AJRCCM. Hong Kong has been respected as the leader in the Control of Tuberculosis not only in SE Asia, but also world wide since the mid 70's. Hong Kong as a British colony has always been very humble and remained low profile despite her achievement made in the control of Tuberculosis.

With the very encouraging results in front of the administrators, the M&H Department postulated at that time that the notification rate could be reduced in about 10-15 years time to less than 25 per 100,000 population, the rate of a low prevalence country as defined by the WHO, similar to that of UK and US. It was really a dream only. Because of the relaxation in control measures, the rate of decline of Tuberculosis in Hong Kong has been slowed down (see attached graph) since the mid 80's and there has been a tendency to rise in the late 90's. Many experts in control of Tuberculosis have underestimated the destructive ability of the Tubercle Bacilli. US also learned a good lesson in the early 90's. As control measures became less vigilant, the incidence of Tuberculosis immediately soared in the US. The Government injected a lot of resources including manpower to bring the incidence back to the mid 80's level. Tubercle Bacilli are known to be weak bacilli. If not, all human beings would have been extinguished on earth long ago. These bacilli are however very endurable. If control measures are less effective, they can grow rapidly and cause mortality and mobility not only to that city or country but to all corners of the world as air travel is so convenient nowadays.

In Hong Kong SAR, the notification rate has been consistently above 100 per 100,000 population in the past 5 years which the WHO has graded as the rate of high prevalence country. After the riot in 1967, the economy has been recovering rapidly in Hong Kong in the 70's. In the 80's, Hong Kong's economy was actually blooming. This has persisted throughout the 90's. The incidence of TB should be inversely proportional to the wealth, but unfortunately Hong Kong is an exception. The main reason was that control measures had been relaxed and slowed down in the mid 80's and the research work between Hong Kong Chest Service and the TB & Chest Unit MRC of UK had been terminated also around that time. The active propaganda against Tuberculosis done in the 60's and 70's has not been seen again in the recent decade.

Health officials from Hong Kong / HKSAR have emphasized repeatedly that the persistently high notification rate was due to the aging population and the increase in life expectancy. However, it is noted that the population is aging all over the world except in the developing countries in the third world. Therefore, this should not be the excuse. Despite that the notification rate of Tuberculosis in HKSAR continues to decline for all ages except those above 60 in the recent 10-20 years, the rate of decline is unsatisfactory if we are considering the wealth and resources that we have been possessing.

2. Control of Tuberculosis

There are 3 important aspects of control of Tuberculosis. They are interrelated and must be practiced simultaneously to achieve maximum control.

Treatment

A. Prevention

  1. BCG vaccination. This has been practiced worldwide. When the disease is endemic, it has been demonstrated that it has a protective effect of around 70% and the effect will last for 5-10 years. BCG was introduced into Hong Kong in 1952. Since then, the rate of Tuberculosis in young children especially those with meningitis has declined significantly. The vaccine has been showed to be effective for primary prevention, but not for secondary prevention. Hong Kong according to WHO recommendation has abandoned the revaccination programme for primary school children since 2000.

  2. Chemoprophylaxis. This is a very selective programme. It is practiced in countries where the incidence of Tuberculosis is very low e.g. USA with a notification rate less than 10 per 100,000 population. In Hong Kong, a study has been done for Silicotic patients but the results were not impressive. The role in other diseases such as autoimmune diseases or patients on long term immunosuppressive therapy has not been well documented. Recently, it has been advocated in technically advanced countries to treat latent Tuberculosis. Its value in HKSAR and the mainland of China has not been established.

B. Case finding. This is also an important tool in the control of Tuberculosis as infective cases could be identified as soon as possible and put under treatment with minimal delay, thus reducing the transmission of patients with active cases to the public.

In HK/HKSAR, case finding rate among close contacts (household contacts) has been persistently low, only 1-2% in the past many years. This could be explained by the fact that Hong Kong has made significant progress in housing for the past 30-40 years. It is unusual to see a family of 3 generations and more than 10 members sleeping in a room as in the 40's and 50's. Rapid economic growth over the same period of time has improved the quality of life in this small-industrialized city and air conditioning of public area and transport is the trend. However as Tuberculosis is still endemic in HKSAR, air conditioning might facilitate its spread. Therefore it is not infrequent that the source of infection cannot be identified.

C. Treatment. Prompt and appropriate treatment is by far the most effective way in preventing the spread of the disease. Therefore high index of suspicion, rapid and accurate diagnosis, prompt and effective treatment are prerequisite in the prevention of the spread of the disease. For most patients, the disease could be brought under control with two to three weeks of treatment. Symptoms will be much improved and the infectious risk will be much reduced. A full course of anti-Tuberculous treatment will however require 6 months of treatment. In order to ensure that patients have taken the drugs faithfully, supervised treatment or DOT (Direct Observed Treatment) is advised. Modified supervised treatment should be allowed in patients who are likely to have good drug compliance and co-operative parents.

Most children with tuberculosis will present with primary Tuberculosis - a subpleural lesion (Gohn's focus) with hilar and mediastial lymph nodes (LNs). The LNs may compress on the adjacent bronchi causing collapse and at times even eroded into the bronchi causing endobronchitis and bronchial stricture. The tuberculosis in children is usually non-open (Non-infective TB) and they usually respond well to treatment except those with TB endobronchitis.

The first line drugs for treatment of Tuberculosis are :

Adult daily dose

Children daily dose

Isonizoid (H)

300mg

10mg/Kg BW not exceeding 300mg

Rifampicin (R)

450-600mg

15mg/Kg BW not exceeding 450mg

Pyrazinamide (Z)

1.5-2 Gm

35-40mg/kg BW not exceeding 1.5Gm

One of the following companion drugs should be added in the initial intensive phase:

*Ethumbutol

15mg/kg

15mg/kg

#Streptomycin

0.5-0.75Gm

20mg/kg not exceeding 0.75Gm

Ofloxacin

600mg

Avoided

*Ethambutol should only be used in children mature enough to report any change in visual acuity.

#Streptomycin should only be used in children mature enough to report the neural side effects of the drug.

The initial intensive phase should as far as possible to include the three potent drugs HRZ plus one companion drug for 2 months to be followed by HR up to six months.

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