Purpose: The objective of this review was to 1) identify existing peer-reviewed literature on the severity and incidence of LTHO associated with human listeriosis; 2) qualitatively evaluate the strength of the evidence, and 3) identify potential data gaps.
Methods: An extensive search of the online PubMed electronic database was conducted to identify primary research on LTHO from human case-control, case-series and cohort studies. LTHO were defined to be symptoms that persist for at least six months after infection. Following a two-stage relevance screening, a full article review was conducted to qualitatively assess relevance and quality and extract data to be summarized.
Results: Of 465 identified articles, the majority of studies were individual cases studies and only 32 met the inclusion/exclusion criteria. Less than half of included studies specified length of follow-up (9% < 1 year; 38% > 1 year). Outcomes most commonly reported were CNS sequelae (93.8%), although 22% of studies mentioned other sequelae. Half of the studies reported paralysis or palsy. Non-CNS sequelae observed included chronic lung disease and increased cancer risk.
Significance: Few studies evaluating outcomes of listeriosis have been conducted, particularly in the last ten years. CNS sequelae are well documented but additional LTHOs are not well understood. Studies featuring long-term follow-up are needed to determine the burden of residual effects following human listeriosis.