Tuberculosis in Singapore

We've been having a bit of a bug fest recently. News about HIV, Chikungunya etc....and the resurgence of Tuberculosis. From this month (1/12/2008), the Ministry of Health will place TB under Schedule 6 of the Infectious Disease Act, only the second infection to be so honoured. The first was Severe Acute Respiratory Syndrome (SARS).

"Placing TB under the Sixth Schedule of the IDA enables MOH to disclose particulars of the TB patient to the relevant authorities in a timely manner. Preventive measures can then be implemented without delay. These include:

• Contact tracing for infectious TB patients who have travelled on long-haul flights,
• Prohibition of infectious TB patients from travelling on commercial flights, and
• Management of recalcitrant TB patients to undergo treatment"

Unlike the SARS virus, the TB bacteria (Mycobacterium tuberculosis) is a very old bug...and has probably been co-evolving with us for thousands, perhaps millions of years. Through all these years it has learnt how to deal with us. It probably enters our body through a lung infection and then subsequently remains dormant for long periods of our lives. In most people, it never awakes from its apparent slumber (latent TB). But in some individuals whose immunity has been weakened in some way, it re-emerges/re-activates and seeds itself into various organs. If untreated at this time, it eventually consumes the patient. The TB bacteria is usually not very infective and is very slow growing. But it has learnt how to survive in our bodies without being detected by our immune system, Even when activated it hides, multiplies and sleeps in the immune cells that are supposed to kill it. Despite having been immunized and even having immunity to TB, most of us continue to harbour the bacteria in what is called the 'primary focus' within our bodies. Latent infections like this is not infectious, but may at some time become activated to the infectious form. More about TB here (Wikipedia) .... and here (MOH FAQ). TB can be treated...but the problem is because it is such a slow bacteria, drug treatment over a long period of time is required. Patients often default and this contributes to the chance of the bacteria developing resistance to good anti TB drugs.The vaccination we receive as babies in Singapore, (BCG; Bacillus of Calmette and Guérin) has been very effective in preventing the TB meningitis of babies, but later on in life, its activity is very much attenuated, we many of us pick up some TB focus at some time in our lives.

The problem globally and in Singapore is that the incidence of TB is increasing. The projected incidence of Singapore TB in 2008 is 38.4 per 100,000, which is higher than the 35.1 per 100,000 in 2007. Most of this increase is thought to be due to re-activation.