Mycobacterium tuberculosis (rarely M. bovis).
Weeks to years
Initial infection usually goes unnoticed—latent TB infection (LTBI). Approximately 10% of those with LTBI will eventually progress to active disease, and half will do so in the first 2 to 3 years following infection. Immunocompromised patients (e.g. HIV infection, diabetes mellitus) are at higher risk for developing active TB.
Sputum bacteriologically positive, drug-susceptible pulmonary TB is considered non-infectious after two weeks of effective therapy. (Multi-drug resistant TB may require a longer period of effective therapy before cases become non-infectious).
Non-pulmonary TB (except for laryngeal TB) is not infectious.
Airborne. Rarely through unpasteurized milk (M. bovis).
- The TB incidence in the local Singapore population (i.e. citizens and permanent residents) rose for the first time in ten years to 40 per 100,000 in 2008 and 39 per 100,000 in 2009. Prior to this, the TB rate of the local population had declined steadily from 57 per 100,000 in 1998 to 35 per 100,000 in 2007. TB continued to be a disease of older males. The TB incidence rate among Malays remained the highest among the three main ethnic groups.
- The majority (83.6%) had pulmonary TB. The two commonest extrapulmonary sites were the pleura and the lymphatic system.
- The number of TB cases among foreigners in Singapore has increased since 2005. In 2009, long-term immigration pass holders comprised 20.8% and short- term pass holders 21.9% of all notified TB cases in the country.
- In 2009, the proportion of primary drug resistance among new pulmonary TB cases in Singapore residents examined was 6.6%. Streptomycin resistance was the most commonly encountered. The proportion of multi-drug resistant (MDR) tuberculosis among new pulmonary TB cases in Singapore residents examined has remained very low, at 0.3%. The MDRTB rate is, however, 10 or more times higher among foreigners reported with TB in Singapore, i.e. 3% among Indonesians and those from the People’s Republic of China, 4% among
Vietnamese and 6% among Burmese.