Explainer: a brief history of TB in Hong Kong, as experts fear global comeback of the disease

Tuberculosis, or TB, was once one of the most deadly diseases in Hong Kong and other Asian cities, and still leaves a lingering fear among older generations.

Many traditional television dramas featuring the period when the “white plague” was a threat often had scenes of patients coughing up blood, which signified a virtual death sentence.

A breakthrough came in the 1950s when big strides were made in the battle against the disease. First, a cure was discovered; second, the colonial government started a partially effective vaccination programme for newborns; and third, hygiene in Hong Kong improved dramatically. These measures helped stop the spread of the global threat, with public attention and media coverage fading away over time.

Despite the improvements, the disease never really left the city. Outbreaks still happen from time to time, with more than 4,412 people becoming infected and about 155 dying every year. About 10 school outbreaks have been recorded every year, according to the Department of Health.

In recent years, experts have expressed fears of a global comeback of the disease, complicated by the fact that there has been a rise in the number of drug-resistant cases, frequent travels between disease hotspots and very crowded and cramped living environments.

Eight cases of tuberculosis confirmed at Hong Kong secondary school

A recent outbreak in a Sha Tin secondary school, Kiangsu-Chekiang College, that infected eight people has again exposed the risks of the disease and left questions over whether the government is doing enough to prevent it. Overseas experts have urged the Hong Kong government to show more commitment in responding to the World Health Organisation’s strategy to eliminate TB by 2035.

A HISTORY OF TB IN HONG KONG

After the second world war, when Hong Kong was crowded with poor immigrants living in slums with poor sanitation and hygiene, TB was rampant. In 1951, the number of deaths peaked at 4,190, and with a high incidence rate of 208 for every 100,000 of the population.

Since the 1940s, the government has been fighting TB with the help of the Hong Kong Anti-Tuberculosis Association, and poured resources into treatment and control services, which led to the building of the Ruttonjee Sanatorium.

Currently, the incidence rate of the disease in the city has dropped from 70 for every 100,000 in 2011 to about 60, and has remained relatively stable for a few years.

The number is still higher than in neighbouring cities and countries however. In Taiwan, the number was recorded at 43 last year, while the figure for Singapore was 44, according to the WHO.

A TICKING TIME BOMB IN THE REGION

Experts have expressed concern about a possible comeback of the disease. Despite the improving figures in Hong Kong, the city is a buzzing hub of travel and a crossroads for travellers coming from disease hotspots.

Five Asian countries are among the seven responsible for 64 per cent of the world’s 10 million new cases of TB last year – China, the Philippines, Indonesia, India and Pakistan. The other two are South Africa and Nigeria.

Experts fear return of Hong Kong’s No 1 killer, TB, amid rise in visitors from disease hot spots and drug resistance

With 1.7 million deaths worldwide last year, TB remains a major public health issue for the world, and especially so in this region.

WHAT IS TB AND HOW IS IT TRANSMITTED?

TB is a disease caused by a germ called Tubercle bacillus or Mycobacterium tuberculosis. It usually affects the lungs, but can also affect other parts of the body, including the lymph nodes, bones, joints, vertebral spine, brain and kidneys.

The illness can be spread through the air from one person to another, often when a patient coughs or sneezes, which releases small droplets containing the germs into the air.

Prolonged exposure is usually required for the disease to be transmitted, according to Dr Leung Chi-chiu from the Centre for Health Protection’s tuberculosis and chest service department.

The WHO says a quarter of the planet’s population has been infected with latent tuberculosis and about 10 per cent will become full-blown cases at some point, especially in those aged 65 or above.

In Hong Kong, Leung said only five per cent of those infected would develop TB-linked diseases due to good personal immunity. As for the rest, the infection will remain dormant and it is not likely any illness will appear, nor will it be transmitted to other people.

However, there is still a one in 10 chance of it becoming active, especially when a person’s body resistance is reduced.

THE SYMPTOMS

- Chest pain

- Pain with breathing or coughing

- Fatigue

- Fever

- Night sweats

- Chills

While coughing up blood is often linked to the contagious illness, the doctor clarified that patients should not see it as a sign of something sinister.

“Experiencing blood-streaked sputum may just mean an inflammation of the blood vessels inside the walls of the lungs. It is common in many minor respiratory illnesses,” Dr Leung said.

Why Hong Kong lags behind Taiwan in the war against tuberculosis

He said the infectious disease is commonly seen in schools, offices and nursing homes because the symptoms are often regarded as a simple cold and are overlooked. Those who encounter coughing that lasts three weeks or more must consult a doctor and ask about the possibility of the bacteria, he warns.

DIAGNOSIS AND TREATMENT

The tests used by doctors to diagnose TB include chest X-ray examinations and sputum examinations. Once diagnosed, drugs have to be taken for at least six months to a year because TB bacteria die very slowly.

There is also the BCG vaccination, but Leung warned the protection offered by this is only partial. Early diagnosis is always the best measure, he said.

“Tuberculosis needs to be treated early in order to prevent deterioration of the disease and spread of the infection,” Leung said.

PREVENTION BY SCREENING AND CONTACT TRACING

In the Sha Tin school outbreak, one pupil was thought to have caught the disease during the summer holiday. The patient then infected six of his schoolmates and one teacher. Subsequently, screening was arranged for 70 of the students and teachers who had contact with the patients. But the school said it was not enough and urged the government to screen all 1,000 members of the school in fear of a further spread.

The slow response by the government has exposed a flaw in the screening and contact tracing system, with health authorities failing to identify those who may be at risk of being infected, and reluctant to offer a large-scale screening.

“Taiwan’s experience in tuberculosis elimination and preventive control can serve as a valuable reference for health care authorities in Asia,” Dr Huang Yi-wen, chairman of the Taiwan Society of Tuberculosis and Lung Diseases, said.

In Taiwan, there was a significant drop from 72.5 infected people per 100,000 a decade ago to 43 last year, according to WHO statistics.

That was thanks to a sound contact tracing system, screening programme and preventive treatment that cost the Taiwanese government HK$2 billion a year, says Dr Anita Chan Pei-chun from Taiwan’s Centres for Disease Control (CDC) under its Ministry of Health and Welfare.

The island has had a system in place to trace patients’ contact, including individuals who have come into contact with a tuberculosis patient at home, in the office or at leisure.

Anyone with an eight-hour window of exposure to a patient within a day, or a cumulative 40-hour exposure in a week, is considered at risk.

With each tuberculosis patient in Taiwan, about 12 to 15 close contacts are usually traced. They are then screened and given preventive treatment.

Through the programme, carers reach out to these people for follow-ups and deliver preventive drugs to their homes or workplace for free.

As a pre-emptive move, Taiwanese authorities also carry out screenings regularly for the elderly in nursing homes, a group deemed most susceptible to the disease.

In comparison, Hong Kong usually only identifies and screens members in a patient’s household, meaning only two to four other contacts are likely to be traced.

Those diagnosed with latent tuberculosis need to visit a public clinic daily on their own to take preventive pills over a nine-month period, and only half of them complete the long treatment, according to government data.

“Any government that cares about the health condition of the poor should enhance tuberculosis prevention, which is the most effective form of public health protection,” Chan said.