On 5 August 2019, local primary care epidemiologists at the Aljarafe Health District in the province of Seville, Andalusia, notified to the SVEA three cases of food poisoning that had occurred in the previous week. One case was hospitalised; this patient’s blood culture later revealed L. monocytogenes growth. In the following days, five additional clusters comprising a total of 32 cases were notified in Seville and one adjacent Andalusian province, and the same pathogen was identified in two of those clusters. These events prompted the local health authorities’ response on 7 August, with instructions to intensify the epidemiological surveillance and environmental sampling in certain food establishments.
By 9 August, the aggregate patient count had reached 22, which included four other cases requiring hospitalisation. In the following days, given the information from epidemiological interviews, in conjunction with microbiological results from non-human samples, the regional government constituted a multidisciplinary committee to investigate the outbreak, comprised of professionals from epidemiological surveillance, healthcare (including urgent care and infectious diseases), microbiology, food safety, and health authorities.
The aim of the outbreak investigation was twofold: (i) to identify the causative agent and the source of infection in order to prevent any further cases and (ii) to discover the reasons behind such a rapid progression of the outbreak. Here, we describe the outbreak and the epidemiological, microbiological and environmental investigations that were carried out to answer these questions.
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