BACKGROUND: For a continuing London outbreak of isoniazid mono-resistant tuberculosis (TB), we aimed to determine transmission rates and risk factors for contacts of early cases, in order to inform future guidance on contact tracing. METHODS: Paper-based proformas were completed by TB nurses, and then analysed using EpiInfo/SAS statistical software. RESULTS: Forty community contacts (11%) became cases, 45 (13%) were recommended chemoprophylaxis and 270 (76%) were discharged clear of infection. The highest transmission rate was among contacts exposed to two or more cases (29% became cases) and close contacts of sputum smear-positive cases (22%). Other risk factors were being male and exposure to drug-using cases or cases with prison links. The number needed to be screened (NNS) to detect one case was lowest [5 (95% CI: 4-8)] for contacts of sputum smear-positive pulmonary cases, although the NNS was still only 20 (95% CI:8-72) for casual contacts of smear-positive cases. CONCLUSIONS: Transmission of disease to contacts was high (11%) compared with other documented outbreaks (0.7-2%). The results support recommended guidelines for contact tracing but also provide grounds to recommend, for outbreak cases, screening of casual contacts of smear-positive cases and contacts exposed to more than one case, drug users or prisoners.
BACKGROUND: For a continuing London outbreak of isoniazid mono-resistant tuberculosis (TB), we aimed to determine transmission rates and risk factors for contacts of early cases, in order to inform future guidance on contact tracing. METHODS: Paper-based proformas were completed by TB nurses, and then analysed using EpiInfo/SAS statistical software. RESULTS: Forty community contacts (11%) became cases, 45 (13%) were recommended chemoprophylaxis and 270 (76%) were discharged clear of infection. The highest transmission rate was among contacts exposed to two or more cases (29% became cases) and close contacts of sputum smear-positive cases (22%). Other risk factors were being male and exposure to drug-using cases or cases with prison links. The number needed to be screened (NNS) to detect one case was lowest [5 (95% CI: 4-8)] for contacts of sputum smear-positive pulmonary cases, although the NNS was still only 20 (95% CI:8-72) for casual contacts of smear-positive cases. CONCLUSIONS: Transmission of disease to contacts was high (11%) compared with other documented outbreaks (0.7-2%). The results support recommended guidelines for contact tracing but also provide grounds to recommend, for outbreak cases, screening of casual contacts of smear-positive cases and contacts exposed to more than one case, drug users or prisoners.
Authors: N Sarita Shah; Courtney M Yuen; Moonseong Heo; Arielle W Tolman; Mercedes C Becerra Journal: Clin Infect Dis Date: 2013-09-24 Impact factor: 9.079
Authors: Graham H Bothamley; Michelle E Kruijshaar; Heinke Kunst; Gerrit Woltmann; Mark Cotton; Dinesh Saralaya; Mark A Woodhead; John P Watson; Ann L N Chapman Journal: BMC Public Health Date: 2011-11-28 Impact factor: 3.295
Authors: Esther L Hamblion; Arnaud Le Menach; Laura F Anderson; Maeve K Lalor; Tim Brown; Ibrahim Abubakar; Charlotte Anderson; Helen Maguire; Sarah R Anderson Journal: Thorax Date: 2016-08 Impact factor: 9.139
Authors: Catherine M Smith; Suzan C M Trienekens; Charlotte Anderson; Maeve K Lalor; Tim Brown; Alistair Story; Hannah Fry; Andrew C Hayward; Helen Maguire Journal: Euro Surveill Date: 2017-02-23