Outbreaks Where Food Workers Have Been Implicated in the Spread of Foodborne Disease. Part 4. Infective Doses and Pathogen Carriage

Abstract

In this article, the fourth in a series reviewing the role of food workers in foodborne outbreaks, background information on the presence of enteric pathogens in the community, the numbers of organisms required to initiate an infection, and the length of carriage are presented. Although workers have been implicated in outbreaks, they were not always aware of their infections, either because they were in the prodromic phase before symptoms began or because they were asymptomatic carriers. Pathogens of fecal, nose or throat, and skin origin are most likely to be transmitted by the hands, highlighting the need for effective hand hygiene and other barriers to pathogen contamination, such as no bare hand contact with ready-to-eat food. The pathogens most likely to be transmitted by food workers are norovirus, hepatitis A virus, Salmonella, Shigella, and Staphylococcus aureus. However, other pathogens have been implicated in worker-associated outbreaks or have the potential to be implicated. In this study, the likelihood of pathogen involvement in foodborne outbreaks where infected workers have been implicated was examined, based on infectious dose, carriage rate in the community, duration of illness, and length of pathogen excretion. Infectious dose estimates are based on volunteer studies (mostly early experiments) or data from outbreaks. Although there is considerable uncertainty associated with these data, some pathogens appear to be able to infect at doses as low as 1 to 100 units, including viruses, parasites, and some bacteria. Lengthy postsymptomatic shedding periods and excretion by asymptomatic individuals of many enteric pathogens is an important issue for the hygienic management of food workers.

Genomic Variability of Serial Human Isolates of Salmonella enterica Serovar Typhimurium Associated with Prolonged Carriage

“…In previous studies, the risks of household transmission of Salmonella ranged from 6% to 39% (33,34). The prolonged shedding of NTS postinfection is an important issue, as evidenced by sporadic outbreaks traced back to asymptomatic carriers as the source of infection (35)(36)(37). These findings have important implications for the detection of possible transmission events suspected by public health genomic surveillance of S. Typhimurium infections.…”

Intervention strategies for the reduction of microbiological contamination on the hands of food handlers

“…In 2011 in the United States, an outbreak involving Escherichia coli O157:H7 in which one person died and twelve people became ill was attributed to improper handwashing (Herzog, 2011). Todd et al (2008), analyzed 816 foodborne outbreaks and found that improper handwashing played a large role in the outbreaks.…”

Comparison of the Activity of Alcohol-Based Handrubs Against Human Noroviruses Using the Fingerpad Method and Quantitative Real-Time PCR

“…Hands are known to be an important vehicle for the transmission of NoV (Bidawid et al 2004;Todd et al 2008;Moe et al 2001), and the use of hand hygiene products that are effective at removing or inactivating NoV is likely to be a critical part of an effective NoV infection control strategy (Bidawid et al 2004;Lages et al 2008;Kampf et al 2005). Despite the important role of hands in the transmission of NoV, little is known about the efficacy of hand hygiene practices in reducing the spread of NoV.…”