Tuberculosis is a serious bacterial disease. It is transmitted from an infected person by droplets. It can also spread directly. The organism may stay silent or "latent" for a long period with the body's inflammatory response walling it off in a "tubercle" or "granuloma".

Latent disease can progress to “active” disease under certain conditions.

The facts:

• Globally, one in three people (mostly in low and low-middle income countries) have latent TB.
• Of these, only 1 in 10 will get active disease.
• Of those with active disease, only 1 in 10 will ever be infectious to other people.
• Those exposed as children are more likely to experience active disease later in life.

Vaccination is available for the prevention of TB. It is called BCG (Bacille Calmette-Guerin).

The vaccination is commonly provided in countries with high rates of TB. It is usually given shortly after birth.

Use of the vaccine is very much restricted in countries with low levels of TB. The benefit of BCG vaccination has been found to be marginal in countries with a low burden of disease. It was routinely used in Australia up to the mid 1980’s and is only provided under special circumstances now.

BCG vaccination might be considered in some situations.

Small children (under 6 years) visiting countries where the prevalence of TB is high

The BCG vaccine protects young children against the severe forms of TB. These include TB meningitis, TB septicaemia and miliary TB (widespread TB in the lungs). If a child has been vaccinated, the disease is usually much less serious or life threatening.

Top 20 countries by actual numbers of TB cases:

Angola, Bangladesh, Brazil, China, DPR Korea, DR Congo, Ethiopia, India, Indonesia, Kenya, Mozambique, Myanmar, Nigeria, Pakistan, Philippines, Russian Federation, South Africa, Thailand, UR Tanzania, Viet Nam

An added 10 by incidence:

Cambodia, Central African Republic, Congo, Lesotho, Liberia, Namibia, Papua New Guinea, Sierra Leone, Zambia, Zimbabwe

Expatriate workers

Expat workers who may be spending long periods of time in countries with a high prevalence of the disease and known multidrug resistant TB.

TB and the role of BCG vaccination should be discussed with all expatriate workers who are being relocated to low and low middle-income countries. In most cases, BCG vaccination will not be recommended. Instead, a baseline test for TB status might be undertaken. This is very important for those who might have lived for long periods of time in high prevalence areas previously. It is better to know their status prior to an overseas placement rather than to have the dilemma of a positive test on return.

Follow up of a positive test on return is very important, particularly in those who might have health issues which might predispose to active disease in the future.

Thirty countries have been identified as high multidrug resistant countries by WHO. Current international trends are available at WHO.

Pre-existing health issues where latent infection might progress to active disease.

• Immunosuppressive medication (eg inflammatory bowel disease, rheumatoid arthritis)
• HIV infection
• Organ transplantation
• Substance abuse (drugs, alcohol)
• Diabetes
• Low body weight
• Silicosis
• Some forms of cancer
• Severe kidney or liver disease

An excellent resource for TB has been provided by CDC.