Lassa fever outbreak and contact tracing in Lagos State, Nigeria, January 2016

Introduction : lassa fever is an acute viral haemorrhagic illness caused by Lassa fever virus. Primary infection can occur by ingesting or inhaling excreta from the multi-mammate rat. On January 15th 2016, Lagos State reported its first case of Lassa fever (LF) following an outbreak in Nigeria which started in August 2015 and affected more than 26 out of 36 states. We investigated to confirm the outbreak, characterize it, and institute public health actions. Methods : we traced contacts among community members, family, caregivers and healthcare workers and classified as high or low risk based on responses to a standardized questionnaire assessing contact directly or indirectly with a case. We used IDSR standard case definition for LF to identify and line-list cases we captured socio-demographic and clinical information of the cases. All contacts of confirmed cases were also line listed and followed up for 21 days. Results : we identified 4 cases (all-laboratory confirmed), and two deaths (CFR: 50%). The mean age 34.75 ± 11.9 years, two were female. The cases were not epidemiologically linked and two of them were imported from other states. There was evidence of rat infestation in their homes. We line listed 700 contacts from 6 Local Government Areas (LGA): Ikorodu - 207 (29.6%); Ifako-Ijaye – 100 (14.3%); Mushin - 18 (2.6%); Eti-Osa - 69 (9.9%); Alimosho - 41 (5.9%); and Amuwo-Odofin - 220 (31.4%). Five (0.7%) contacts were epidemiologically linked to Ogun State. Conclusion : outbreak of LF in Lagos State was confirmed, it was controlled through active case search, effective contact tracing and strict infection control. We sensitized the community and health workers in Lagos State on LF. We recommended that surveillance of LF should be strengthened and efforts at environmental sanitation should be intensified.