Infectious disease: Rates of tuberculosis infection may be rising in pockets of north Dublin, according to a novel study involving collaborative US and Irish research.
Preliminary results from an ongoing study between the Department of Microbiology at the Mater hospital, Dublin and the Departments of Infectious Diseases and Geographic Medicine at Stanford University Medical School California, suggest tuberculosis (TB) levels are on the increase among young Irish-born males in parts of Dublin.
While national TB rates are steady at a level of 9.7 cases per 100,000 population, rates of 18-19 cases per 100,000 population had been recorded for both the inner city and areas of north Co Dublin.
However, this latest study found TB rates of between 20 and 30 cases per 100,000 for both inner city and parts of Fingal, Co Dublin, leading to concerns that we may be seeing the beginning of an epidemic of infectious TB in the areas.
TB exists in two distinct forms. Active TB, in which the person has symptoms and can infect others, has a high death rate if left untreated.
Latent TB, in which the person carries the bug but is not affected by it, is a dormant form of infection with only a 10 per cent lifetime risk of developing full-blown, active TB.
Using state-of-the-art molecular medicine techniques, the researchers from Dublin and California took samples from newly diagnosed cases of TB in community care areas 6, 7 and 8 (corresponding to the north inner city and Fingal areas of Co Dublin) and identified the exact subtype of TB involved in each case.
The techniques allow the classification of TB into cases of recently transmitted infection and cases where reactivation from latent disease had occurred. Of 102 samples analysed to date, 55 per cent have been identified as clusters involving recent transmission of infectious TB. The majority of these were among young males, born in the Republic.
When the molecular techniques were combined with contact tracing, the researchers identified a number of clusters of infection centred around a ferry, pubs and schools.
The TB strain traced to a ferry was found to have infected relatives and friends of the patient as well as co-workers on the ferry.
A person with TB who worked in a pub was linked through it to a further 14 people with the infection using molecular identification.
According to the researchers, who included Dr Elizabeth Fair of Stanford University and Dr Margaret Hannon, consultant microbiologist and epidemiologist at the Mater hospital, Dublin "Classic risk factors (such as HIV infection, multiple drug resistant TB, intravenous drug use and immigration) are not predictive of TB in the Republic."
However, research from the former national TB centre at Peamount Hospital, published in the February issue of the Irish Medical Journal, found that while the overall incidence of TB here had decreased, in relative terms the caseload of drug resistant TB had increased.