TB Rising with Ageing Populations in East Asia
In Japan, Hong Kong (China) and Singapore, where the proportion of elderly people has more than doubled in the last few decades, about half of TB cases currently occur among those aged 50 and over. (For exact figures, see below.)
These countries have high TB rates relative to their level of development - far higher than European nations with a similar gross domestic product. Japan, which has more elderly people than children, has one of the world's highest TB rates for a developed nation.
But these high rates are also related to other factors. In Japan, the homeless and economically disadvantaged are vulnerable to TB infection. The TB rate among these groups in urban areas is about 50 to 60 times higher than among the general population, studies by Japan's Research Institute of Tuberculosis (RIT) have shown.
Urbanization and overcrowding may be factors in some areas. Also, greater attention from the medical community is needed - many doctors in Japan, for example, are not that aware about the country's TB situation.
Migration has also had a minor impact on these countries' TB rates. The impact of migration is even more prominent in Brunei and Malaysia, where foreign workers are plentiful. With their relatively young populations, ageing has had less importance in these two nations.
WHO has warned the numbers could soar in future. "TB is an infectious disease. From the elderly or foreign workers it can spread to the general population," said Dr Shigeru Omi, Regional Director for WHO's Western Pacific Region.
Many elderly people sick with TB in East Asia were probably infected when young, at a time when TB was rampant in these countries. In 1950, about half of all Japanese adolescents were infected, according to RIT estimates. Compare this to figures for 1995, when only 1% of youths under 20 years in Japan were infected.
Infection with TB germs - known as bacilli - does not necessarily cause sickness. Those infected may fall ill years later though, when their immune systems weaken - which is why people with AIDS or the elderly are more likely to fall sick with TB.
Discovering their disease may come as a shock. "I didn't know that I had the disease until I came into hospital for lumbago. By then it was already bad," says a 58-year-old patient living in public housing in Tokyo's Shinjuku area. Now on a TB treatment course at a local health centre, he adds, "I had heard of TB before but really knew nothing about it. I didn't know it was once a big problem in Japan."
In Japan in the 1950s, TB was known as the "national disease", with about half a million new TB cases every year. (In 1957, there were about 521 000 new cases of TB in Japan, compared to only 33 000 cases in the United Kingdom). Other East Asian countries also had serious TB epidemics.
In the 1960s, TB rates started falling with better TB control measures and economic development. Now, that epidemic which had its roots half a century ago is resurfacing - alongside an ageing population, is an ageing epidemic.
The greater mobility of people - through migration and travel - has had some impact on TB rates, albeit only minimal in some countries. This may change with the rising number of foreign workers. According to the International Labour Organization, there are 7 million migrants and their families across Asia, but unofficial estimates are much higher.
Migration is strongly linked with the spread of TB in industrialized countries, where often about half of TB cases are among foreign-born people. Moreover, deadly strains of TB that are resistant to drug treatment are spreading this way. In one reported case, a Ukrainian man infected 13 airline passengers with drug-resistant TB during a flight from Paris to New York.
In Brunei, about 30% of TB cases are among foreign workers. In Malaysia in 1997, about 1 in 7 TB cases were among migrant workers. Recent data shows that in Sabah, the state with the most TB cases, 65% of all TB cases occurred among migrants; that figure is 9% in the Federal Territory of Kuala Lumpur. Another factor that may be bumping up TB cases in Malaysia is the escalating HIV/AIDS epidemic. Among people with AIDS in Malaysia, TB is a major cause of death.
In Singapore, non-residents account for a substantial proportion of all TB cases at 31%. In Hong Kong and Macao, this figure is far smaller, but experts still believe that frequent travel of residents to and from mainland China may have some impact on the TB situation.