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Outbreaks Where Food Workers Have Been Implicated in the Spread of Foodborne Disease. Part 9. Washing and Drying of Hands To Reduce Microbial Contamination

As Originally published by Journal of Food Protection,, April 2010

By: Dr. Ewen Todd, et. al.
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During various daily activities at home and work, hands quickly become contaminated. Some activities increase the risk of finger contamination by pathogens more than others, such as the use of toilet paper to clean up following a diarrheal episode, changing the diaper of a sick infant, blowing a nose, or touching raw food materials. Many foodborne outbreak investigation reports have identified the hands of food workers as the source of pathogens in the implicated food. The most convenient and efficient way of removing pathogens from hands is through hand washing. Important components of hand washing are potable water for rinsing and soaps to loosen microbes from the skin. Hand washing should occur after any activity that soils hands and certainly before preparing, serving, or eating food. Antimicrobial soaps are marginally more effective than plain soaps, but constant use results in a buildup of the antimicrobial compound on the skin. The time taken to wash hands and the degree of friction generated during lathering are more important than water temperature for removing soil and microorganisms. However, excessive washing and scrubbing can cause skin damage and infections. Drying hands with a towel removes pathogens first by friction during rubbing with the drying material and then by wicking away the moisture into that material. Paper rather than cloth towels should be encouraged, although single-use cloth towels are present in the washrooms of higher class hotels and restaurants. Warm air dryers remove moisture and any surface microorganisms loosened by washing from hands by evaporation while the hands are rubbed together vigorously; however, these dryers take too long for efficient use. The newer dryers with highspeed air blades can achieve dryness in 10 to15 s without hand rubbing.

This article is the ninth in a series of articles concerning food workers and foodborne illness. In the first three articles, the authors described the types of outbreaks that were identified during a review of 816 outbreak investigation reports and discussed how workers contributed to these outbreaks. In the next three articles, the authors discussed infective doses, pathogen carriage, sources of contamination, pathogen excretion by infected persons, and transmission and survival of pathogens in food environments (72, 220-224). The seventh article contained an outline of the various barriers, some more effective than others, created to prevent microbial and physical contaminants from reaching food during production and preparation (226). The eighth article considered the benefits and liabilities of glove use (225). The present article includes the rationale for hand hygiene and the need for removing as much soil as possible from the hands, the use of different hand soap types, the conditions for effective hand washing, and the importance of complete drying of the hands. After leaving home and arriving at work, food workers must wash their hands effectively before starting food preparation so pathogens are not transferred to food from the home and outdoor environments.

Episodes of diarrhea frequently occur in all populations. In the United Kingdom, an estimated one in five persons experiences an intestinal infectious disease episode per year, with similar rates in the remainder of Europe (237). A telephone-based population survey conducted in 1996 and 1997 across U.S. FoodNet sites revealed about 1.4 episodes of diarrhea per person per year (87) compared with an apparent improvement to 0.72 episodes for the years 1998 and 1999 (95). However, Imhoff et al. (95) stated that the differences probably could be explained by the questions asked (diarrhea alone and vomiting and diarrhea) and the different populations surveyed rather than any real change in patterns. In a later study in four developed countries, Scallon et al. (200) found that at least one episode of diarrhea was reported by 7.6% of respondents in Canada, 7.6% of respondents in the United States, 6.4% of respondents in Australia, and 3.4% of respondents in Ireland for a 4-week study period. These percentages translate to approximately one episode of diarrhea per year for each person in the United States and Canada and a slightly lower rate for Australia. These surveys indicate that the incidence of intestinal infectious disease with diarrhea is unacceptably high for developed countries.

A large percentage of these illnesses are contracted in the home (28). Child care givers in England washed their hands with soap after changing a dirty diaper only on 42% of observed occasions, and one in five toilet users did not wash their hands with soap afterward (43). After diapers were changed, fecal contamination was found in living rooms, bathrooms, and kitchens and on faucets and soap dispensers. A study of illness transmission in Boston, MA, households with children enrolled in child care centers revealed that although both gastrointestinal and respiratory illnesses are frequently transmitted between family members, only two-thirds of survey respondents correctly believed that contact transmission was important for spread of colds, and less than half thought contact transmission was important for spread of gastrointestinal illnesses such as the "stomach flu" (121). There was limited understanding of how changing diapers or eating foods prepared by a person with gastroenteritis were risk factors for becoming infected with a pathogen. Parents reported washing their hands very frequently after changing a diaper or using the toilet, although they did not necessarily believe that fecal-oral transmission was important. However, the authors thought it was also likely that the parents overreported the frequency of hand washing after bathroom use because of perceived social expectations. Most respondents used soap; only 8% of respondents reported using alcohol gels "most" of the time following potential fecal contamination of hands. However, the authors stated that the effectiveness of soaps and alcohol against enteric pathogens depends on the agent involved and the product and that alcohol is an excellent virucide when used for rotavirus-contaminated surfaces but is not as effective against noroviruses. Hand washing with plain soap may actually further spread virus contamination.

Food workers may have their hands contaminated from various sources, even if they are not suffering from enteric infections or are asymptomatic carriers. Food workers have their hands frequently contaminated with Staphylococcus aureus (48), Listeria monocytogenes (99), coliforms and staphylococci (92), Escherichia coli (181), and Salmonella (49). Staphylococci are common colonizers of the nasopharynx and can be transferred via mucus and saliva to hands when the face is touched, which frequently occurs (222, 223). Danielsson and Hellberg (46) found that in clinically well meat workers, enterotoxin-producing S. aureus and Staphylococcus epidermidis were present in 22% of nasal swabs, 6% of throat swabs, and 4 of 16 superficial skin lesions. They also found that 42% of workers with "slight colds" harbored staphylococcal species in their noses. Unlike hand contamination with staphylococci from the nasopharynx, the enteric bacteria that contaminate the hands of food workers more often are associated with raw foods of animal origin rather than poor personal hygiene after visiting the toilet. In contrast, workers in plants preparing foods from nonanimal sources, e.g., vegetables, cookies, or chocolate, or in offices or laboratories have relatively few Enterobacteriaceae contaminants on their hands (181, 208). Workers must be particularly dedicated to proper hand hygiene to avoid contamination of foods during preparation.


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Dr. Ewen Todd is a Food Safety Expert with over 45 years of knowledge and experience in general food safety and Food Microbiology Issues. Specifically, he has extensive experience the reporting and surveillance of Foodborne Disease, as well as development of analytical methods for identifying foodborne pathogens. As a result of his work with the industry and his knowledge of foodborne disease, Dr. Todd has influenced research programs and regulatory approaches taken by the Health Protection Branch of Health Canada. In the US, he held the position of Director of the National Food Safety and Toxicology Center and the Food Safety Policy Center at Michigan State University.

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