Diagnosis was based most commonly on the isolation of Listeria monocytogenes in blood culture (71%, 459/647), followed by CSF (24%, 156/647). Where age was reported (n=620), ages range from birth to 93 years (median 26 years) and 39% (241/620) are neonates aged ≤28 days . Of neonatal cases, 96% (232/241) had early-onset disease (birth to ≤6 days). Females account for 55% (341/623) of cases where gender is reported. As of 19 December 2017, case investigation forms (CIFs) of variable completeness have been received for 229 (35%) cases. Apart from neonates (≤28 days) and the elderly (>65 years), additional risk factors for listeriosis reported include pregnancy (11/47 females aged 15-49 years) and HIV infection status. In non-neonatal cases where HIV status was known (n=117), 37% (43/117) were HIV positive. Maternal HIV status is known for 57 neonatal cases, of which 22/57 (38%) were HIV positive. Final outcome data is available for 20% (131/640) of cases, of which 46% (60/131) died. To date, whole genome sequencing has been performed on 206 clinical L. monocytogenes isolates. Fifteen sequence types (STs) have been identified; however, 74% (153/206) belong to a single ST (ST6). Isolates in this ST6 cluster are very closely related, showing <20 single nucleotide polymorphism (SNP) differences. This suggests that most cases in this outbreak have had exposure to a widely available, common food type/source Clinical listeriosis management guidelines are available on the website (www.nicd.ac.za). Where clinicians suspect listeriosis but specimens (including CSF and blood) are culture negative, a polymerase chain reaction (PCR)-based test can be performed at the NICD. Whole genome sequencing is being performed on all clinical isolates and food/environmental isolates received from the NHLS Infection Control Laboratory in Johannesburg.As of 19 December 2017, a total of 647 laboratory-confirmed listeriosis cases have been reported to the National Institute for Communicable Diseases (NICD) since 01 January 2017.