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| TUBERCULOSIS |
Disease
Tuberculosis, one of the oldest diseases known to affect humans, is a major cause of death worldwide. The disease, which is caused by the bacteria of mycobacterium tuberculosis complex, usually affects the lungs but other organs are involved in upto 1/3rd of cases. Transmission usually takes place through airborne spread of droplet nuclei produced by patients infected with pulmonary tuberculosis. Tuberculosis occurs disproportionately among disadvantaged populations such as malnourished, homeless, those living in over crowded and substandard housing. There is an increased occurrence of tuberculosis among HIV positive individuals.
Occurrence
M. tuberculosis infects an estimated 20 -43 % population of the world. Each year about 3 million people worldwide die due to this disease. The WHO estimated that 8.8 million new cases of tuberculosis occurred worldwide in 2005, 95% of them occurring in developing countries of Asia, Africa, Middle East & Latin America. Maximum deaths from tuberculosis also occur in developing countries.
Risk for travellers
Most travellers are at low risk for tuberculosis (TB). The risk for long-term travellers (>3 months) in a country with a higher incidence of TB than their own may be comparable to the risk for local residents. Living conditions, as well as duration of travel and purpose of travel, e.g. emergency relief, are important in determining the risk of infection: high-risk settings include impoverished communities, areas experiencing civil unrest or war, refugee areas, health facilities, prisons and shelters for the homeless. Persons with HIV infection are at higher risk of TB.
Vaccine
All versions of the BCG vaccine are based on live, attenuated mycobacterial strains descended from the original, attenuated bacillus Calmette-Guérin. The vaccine is administered intradermally and can be given simultaneously with other childhood vaccines. BCG vaccine is contraindicated for persons with severely impaired immunity, including individuals with HIV infection.
BCG vaccine is of very limited use for travellers. In the first year of life it provides good protection against forms of TB associated with haematogenous spread (miliary TB and meningitis). In countries with high TB prevalence, infants are generally immunized with a single dose of BCG as soon after birth as possible. Children who are known to be HIV-infected, even if asymptomatic, should not be immunized with BCG vaccine but WHO has recommended that asymptomatic HIV infected chidren residing in endemic areas should receive BCG. Other protective benefits of the vaccine are uncertain. BCG should be considered for unimmunized infants travelling from an area of low incidence to one of high incidence.
Many industrialized countries with a low incidence of TB have ceased giving BCG routinely to neonates.
Booster doses of BCG are never recommended. |
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