Worldwide, tuberculosis (TB) is the most frequent cause of death due to a single infectious agent. It is caused by organisms of the Mycobacterium tuberculosis complex,including M. tuberculosis, M. bovis and M. africanum. All three of these organisms are capable of causing TB in humans.
The disease can take two forms. Pulmonary TB affects the lung and can be transmitted by coughing or sneezing. Non-pulmonary TB is less common than the pulmonary form and can involve any organ or tissue, most commonly bone, lymph nodes, central nervous system, skin and the genito-urinary tract.
Enhanced TB surveillance
Clinicians in Northern Ireland, in line with those in the rest of the UK, are required to notify all cases of TB to the Director of Public Health. Enhanced surveillance of TB was established in Northern Ireland in 1992. All notifications are collated into a Northern Ireland dataset which is validated using laboratory reports and antimicrobial resistance information.
The information is then used for inclusion in national and European reports, as well as for disease surveillance at a local level. An annual report is prepared for the Regional Tuberculosis Sub-Committee and circulated to microbiologists, chest physicians and those with an interest in TB.
Case definitions are based on the recommendations developed by the working group of the World Health Organization (WHO) and the European Region of the International Union Against Tuberculosis and Lung Disease (IUATLD).
- Culture confirmed case: Defined as one in which the diagnosis has been confirmed by culture of M. tuberculosis, M. bovis or M. africanum.
- Other than culture confirmed case: In the absence of culture confirmation, a case with “a clinician’s judgement that the patient’s clinical and/or radiological signs and/or symptoms are compatible with tuberculosis and a clinician’s decision to treat the patient with a full course of anti-tuberculosis treatment”.
Both types of cases should be notified through this surveillance system. Any case which subsequently does not fulfil one of the above case definitions is marked as denotified but remains in the dataset. This would include those with diagnosis other than TB.
- Multi-drug resistance (MDR) is defined as resistance to at least isoniazid and rifampicin, with or without resistance to other drugs.