**2. Health and economic impacts of listeriosis**

*L. monocytogenes* can result in a disease known as listeriosis, to which pregnant women and their newborns, adults aged 65 or older, and people with weakened immune systems are particularly vulnerable [2]. In healthy adults, listeriosis is most likely to manifest as mild gastroenteritis. However, in some instances it can result in more severe symptoms, which can lead to life-threatening illnesses such as endocarditis, encephalitis or meningitis, and severe sepsis [3]. Inadequate food hygiene practices during food preparation are primarily responsible for the propagation of the bacterium and contamination of ready-to-eat (RTE) foods (**Table 1**) during processing, distribution and handling [4]. Small to medium-sized enterprises (SMEs) are more likely to experience *L. monocytogenes* outbreaks than renowned large-scale food processing enterprises owing to differences in the implementation of food safety measures [5].

RTE foods, which are often stored at low temperatures, are the type most susceptible to contamination with *L. monocytogenes* since the bacterium is psychrotrophic and possesses the ability to survive and grow in the presence of many food preservation systems, such as low pH and high salt concentrations [6]. The contamination of minimally processed fruit and vegetable products with *L. monocytogenes* is often a concern, considering that these foods, which are attractive to consumers, are often not subjected to lethal treatments during processing to inactivate potential pathogens [7]. Moreover, the manner in which RTE vegetables are sliced can affect the survival of *Listeria* and the effectiveness of decontamination procedures in the finished products. Hand tearing or manual slicing with a razor blade reduced the survival and growth of *E. coli* and *L. innocua*, probably because of less damage to the vegetable tissues

**Year Foodstuff implicated Country of outbreak**

and minimal leakage of nutrients from damaged plant tissues [8].

2015 Ice cream [66]

72 Listeria Monocytogenes

 Creamy, soft, raw-milk cheeses [2] USA Frozen vegetables [62] USA Raw milk chocolate milk products [63] USA Packaged salad [64] USA Soft cheese [65] USA

 Commercially produced, pre-packaged caramel apples [67] USA Mung bean sprouts [68] USA Soft cheese [69] USA Cheese products [70] USA

2017–2017 Various food products [71] South Africa 2017 Not determined [72] Australia

**Table 1.** Some records of global *Listeria* outbreaks between 2014 and 2017.

2014 Various food products [73] 28 EU/EEA countries

**CDC**: Centre for Disease Control, **NICD**: National Institute for Communicable Diseases, **ECDC**: European Centre for Disease Prevention and Control, **USA**: United States of America, **EU**: European Union, **EEA**: European Economic Area.

Globally, billions of people are at risk every year and thousands die as a result of consuming unsafe food [12]. In the United States of America (USA), listeriosis has been identified as the third leading cause of death from food-borne illness, after non-typhoidal *Salmonella* and *Toxoplasma gondii*, despite its rarity [13]. In Africa, food-borne illness continues to be a major health threat, especially for vulnerable groups such as infants, pregnant women and their newborns as well as immune-compromised individuals such as elderly people and those with HIV/AIDS [14].

In humans, invasive listeriosis is characterized by septicemia, meningitis, and abortion in pregnant women [15]. Listeriosis in pregnant women can result in premature labor, stillbirth, abortion, and neonatal infection, with high neonatal mortality [16]. It should be noted that *L. monocytogenes* infection in healthy individuals does not necessarily result in invasive disease. The incubation period of listeria-related gastroenteritis can range from 1 to 24 days, but the average incubation period has been found to be less than 24 hours. After the incubation period, prominent symptoms will include fever, then diarrhea, arthralgia, myalgia, and headache. Other common symptoms are nausea, vomiting, abdominal pain and watery diarrhea. In healthy individuals, the illness tends to last between 1 and 3 days, with a very low rate of hospitalization [17].

Listeriosis may have an economic impact in the form of costs incurred by the government in funding health institutions to deal with the problem [18]. Other costs can take the form of legal costs emanating from lawsuits imposed on food production companies arising from illness and death due listeriosis [19].
