Why proper glove use is important: Norovirus transfers nicely from inoculated gloves to surfaces and fruit

No bare hand contact rules are often rebutted with "people do dumb things with gloves on."

One of my favorite glove use stories is something a greenhouse manager told me 10 years ago. It goes something like this: the guy had convinced the business owner that food safety was really important and he installed full restrooms in the greenhouse — and fully stocked a closet with latex gloves. The manager trained all the employees on why clean hands and gloves were important.  A week after the training session he saw an employee urinating on the outside of the restroom. With his gloves on.

In this month’s Journal of Food Protection, my friend Jen Cannon’s group has a paper that shows some great data to back up why proper glove use is important: Dirty gloves are pretty decent at transferring norovirus. After looking at multiple donor/recipient surfaces (stuff like dirty gloves to berries, or dirty gloves to food contact surfaces) Sharps and colleagues showed transfer rates from 20%-70% under wet conditions and although less, still showed transfer of up to 12% under dry conditions.

From the discussion, "After a restroom visit, a food worker, not respecting hygienic practices, may immediately or within a short period of time (<30 min) begin to handle foods, not allowing sufficient time for contaminated hands to dry." or take the gloves in to the restroom with them.

Abstract is below.

Human Norovirus transfer to stainless steel and small fruits during handling

Journal of Food Protection®, Volume 75, Number 8, August 2012 , pp. 1437-1446(10)

Sharps, Christopher P.; Kotwal, Grishma; Cannon, Jennifer L.

Human noroviruses (NoVs) cause an estimated 58% of foodborne illnesses in the United States annually. The majority of these outbreaks are due to contamination by food handlers. The objective of this study was to quantify the transfer rate and degree of contamination that occurs on small fruits (blueberries, grapes, and raspberries) and food contact surfaces (stainless steel) when manipulated with NoV-contaminated hands. Human NoVs (genogroups I and II [GI and GII]) and murine norovirus (MNV-1) were inoculated individually or as a three-virus cocktail onto donor surfaces (gloved fingertips or stainless steel) and either immediately interfaced with one or more recipient surfaces (fruit, gloves, or stainless steel) or allowed to dry before contact. Viruses on recipient surfaces were quantified by real-time quantitative reverse transcriptase PCR. Transfer rates were 58 to 60% for GII NoV from fingertips to stainless steel, blueberries, and grapes and 4% for raspberries under wet conditions. Dry transfer occurred at a much lower rate (<1%) for all recipient surfaces. Transfer rates ranged from 20 to 70% from fingertips to stainless steel or fruits for the GI, GII, and MNV-1 virus cocktail under wet conditions and from 4 to 12% for all viruses under dry transfer conditions. Fomite transfer (from stainless steel to fingertip and then to fruit) was lower for all viruses, ranging from 1 to 50% for wet transfer and 2 to 11% for dry transfer. Viruses transferred at higher rates under wet conditions than under dry conditions. The inoculum matrix affected the rate of virus transfer, but the majority of experiments resulted in no difference in the transfer rates for the three viruses. While transfer rates were often low, the amount of virus transferred to recipient surfaces often exceeded 4- or 5-log genomic copy numbers, indicating a potential food safety hazard. Quantitative data such as these are needed to model scenarios of produce contamination by food handling and devise appropriate interventions to manage risk.

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About Ben Chapman

Dr. Ben Chapman is a professor and food safety extension specialist at North Carolina State University. As a teenager, a Saturday afternoon viewing of the classic cable movie, Outbreak, sparked his interest in pathogens and public health. With the goal of less foodborne illness, his group designs, implements, and evaluates food safety strategies, messages, and media from farm-to-fork. Through reality-based research, Chapman investigates behaviors and creates interventions aimed at amateur and professional food handlers, managers, and organizational decision-makers; the gate keepers of safe food. Ben co-hosts a biweekly podcast called Food Safety Talk and tries to further engage folks online through Instagram, Twitter, Facebook, YouTube and, maybe not surprisingly, Pinterest. Follow on Twitter @benjaminchapman.