A Review of Known and Hypothetical Transmission Routes for Noroviruses

Abstract

Human noroviruses (NoVs) are considered a worldwide leading cause of acute non-bacterial gastroenteritis. Due to a combination of prolonged shedding of high virus levels in feces, virus particle shedding during asymptomatic infections, and a high environmental persistence, NoVs are easily transmitted pathogens. Norovirus (NoV) outbreaks have often been reported and tend to affect a lot of people. NoV is spread via feces and vomit, but this NoV spread can occur through several transmission routes. While person-to-person transmission is without a doubt the dominant transmission route, human infective NoV outbreaks are often initiated by contaminated food or water. Zoonotic transmission of NoV has been investigated, but has thus far not been demonstrated. The presented review aims to give an overview of these NoV transmission routes. Regarding NoV person-to-person transmission, the NoV GII.4 genotype is discussed in the current review as it has been very successful for several decades but reasons for its success have only recently been suggested. Both pre-harvest and post-harvest contamination of food products can lead to NoV food borne illness. Pre-harvest contamination of food products mainly occurs via contact with polluted irrigation water in case of fresh produce or with contaminated harvesting water in case of bivalve molluscan shellfish. On the other hand, an infected food handler is considered as a major cause of post-harvest contamination of food products. Both transmission routes are reviewed by a summary of described NoV food borne outbreaks between 2000 and 2010. A third NoV transmission route occurs via water and the spread of NoV via river water, ground water, and surface water is reviewed. Finally, although zoonotic transmission remains hypothetical, a summary on the bovine and porcine NoV presence observed in animals is given and the presence of human infective NoV in animals is discussed.

Occurrence of Norovirus in pig faecal samples in the Eastern Cape, South Africa

“…Swine illnesses are associated with porcine Sapovirus while the influence of Norovirus contagions in swine is unknown [3]. Some strains of Caliciviruses (Norovirus and Sapovirus) have the potential for zoonotic transmission since they are hereditarily related to humans [13] and studies have shown that some domestic pigs serve as the reservoir of these viruses [14].…”

Comparative Virucidal Efficacy of Seven Disinfectants Against Murine Norovirus and Feline Calicivirus, Surrogates of Human Norovirus

“…The primary transmission route is the faecal-oral one, either via person-to-person contact or by consumption of contaminated food or water (Lopman et al 2003;Siebenga et al 2007;Kroneman et al 2008;Scallan et al 2011;Mathijs et al 2012). Noroviruses are very resistant and can persist for several days in the environment (D'Souza et al 2006).…”

“…Noroviruses are very resistant and can persist for several days in the environment (D'Souza et al 2006). Due to this high persistence on various inanimate surfaces and on food, coupled with the prolonged shedding of high amounts of virus in faeces and the low infectious dose, person-to-person transmission is very efficient and noroviruses constitute a serious public health issue (Mathijs et al 2012). Alternatively, food can be contaminated with HuNoV either at the source in the growing or harvesting areas by contaminated irrigation water or during handling or preparation of meals (Tuan Zainazor et al 2010;Mathijs et al 2012).…”

Survival and Transfer of Murine Norovirus within a Hydroponic System during Kale and Mustard Microgreen Harvesting

“…Produce safety is of great concern as fresh produce serves as the major vehicle for huNoV transmission (8,9). Produce that is consumed raw or with little or no processing may become contaminated with huNoV during postharvest handling (e.g., irrigation water and amendments) and processing (e.g., washing and packing) and also through contact with infected individuals who may handle the produce or seeds (10)(11)(12). Previously, huNoV has been detected in surface water and groundwater with various frequencies (13,14).…”

“…Previously, huNoV has been detected in surface water and groundwater with various frequencies (13,14). It is likely that viruses can be spread by water, and internalization of huNoV through root uptake of produce via polluted irrigation water is one of the potential routes for plant contamination (12,14). However, without an appropriate cell culture model, the behavior of huNoV is still not well understood.…”