Tuberculosis: the burden on Asean

 This is particularly true of the Asean region, where six of the 10 member nations – Cambodia, Indonesia, Myanmar, Thailand, The Philippines and Vietnam – are still reporting a high number of new infections every year.

And although TB trends are declining worldwide, albeit slowly, the emergence of multi-resistant bacterial strains is likely to pose an additional challenge to health systems in the near future. 

Tuberculosis is primarily a lung infection caused by Mycobacterium tuberculosis (also known as Koch’s bacillus) but the bacteria can also spread to many other organs. 

Contamination occurs when a person with active TB lung disease releases infected droplets during coughing or sneezing, which are then inhaled by subjects nearby. TB is however much less contagious than the flu and close contacts are needed to pass on the infection – such as among family members living in the same home or among caretakers. 

Anyone can get TB but children younger than 5 years of age, the elderly and people with compromised immunity due to HIV-Aids, malnutrition, IV drug use, diabetes or chemotherapy are at highest risk of developing the severe forms of the infection. Smokers and people exposed to or living in underprivileged shelters as well as refugees camps are also more prone to the disease. 

Schematically, TB can present in three different entities: 

1) Primary infection: This results from the first infectious contact with a sick person. After an incubation of 1 to 3 months, some rare symptoms such as fever and fatigue may be noticed and in 90 per cent of the cases, the body’s immune system is able to eliminate the bacteria leading to a complete cure. 

2) In the remaining 10 per cent, the pathogen remains “silent” in the lung, a condition known as latent or inactive TB that does not induce any symptoms and is not contagious.

3) In about 10 per cent of the cases, the disease progresses to an active form of TB. Active TB can present several months or years after the first contact and is often triggered by an underlying low immunity status. In the majority of cases, the active TB affects the lungs (pulmonary TB) leading to various symptoms such as persistent cough that may produce bloody phlegm, chest discomfort, night sweats, weight loss and low appetite.

Because of persistent coughing, pulmonary TB is the most contagious form of the disease. In about 25 per cent of active TB cases, the bacteria spread through the blood or the lymphatic circulation to other organs and cause specific symptoms linked to the affected system, in particular the brain (meningitis), the bone (especially the spine), the kidneys, liver and heart. Left untreated, active TB is fatal in about 50 per cent of the cases. 

Diagnosis and treatment of TB are complex and anyone with a suspected TB infection, whatever the stage, needs to be referred to a chest physician specialised in TB management. Evaluation of the dissemination of the infection and the selection of appropriate therapy require many tests, among them a skin test (to assess the skin sensitivity to the germs), blood and urine tests, imaging investigations (chest X-ray and possibly CT scan), and sputum exam to isolate the bacillus and test its possible resistance to antibiotics. A survey to screen possible TB infections among acquaintances of the patient is also required.

Treatment relies on combination of multiple antibiotics (from 2 to 4 products) that are usually given for 6 months but may be extended to more than 20 months in case of bacterial multi-resistance. 

The Bacillus Calmette-Guerin (BCG) vaccination, which has been around for more than half of century and is on the World Health Organisation’s List of Essential Medicines, is still the only vaccine used for TB prevention. Often given at birth, its efficacy is estimated at up to 80 per cent against severe TB manifestations among infants while its safety profile is considered very satisfactory. Expatriates from western countries are advised to discuss the rationale for BCG vaccination for their young children upon arriving in the Asean region.

 

 

Dr Gerard Lalande is managing director of CEO-Health, which provides medical referrals for expatriates and customised executive medical check-ups in Thailand. He can be contacted at [email protected]