Norovirus Transfer between Hands and Fresh Produce

Introduction:   Norovirus is a common cause of gastroenteritis worldwide.  Many outbreaks in the US have been attributed to transmission through fresh produce and multi-ingredient foods, which often require significant handling immediately prior to consumption.

Purpose:   To evaluate the effect of gloved and ungloved hands on norovirus transfer during fresh produce preparation.

Methods:   The palm and fingers of bare or gloved hands (polyvinyl, vinyl or nitrile) were inoculated with 0.1 ml (approximately 6 log PFU/hand) murine norovirus (MNV-1) and allowed to dry. Freshly chopped Romaine lettuce was handled by the contaminated hands, and then sampled to determine the transfer coefficient.  MNV-1 transfer was also measured after volunteers handled chopped contaminated lettuce with uncontaminated bare or gloved hands. Hands and gloves were sampled for transferred virus by the glove juice method, and recovered MNV-1 quantified by plaque assay.

Results:   Transfer of MNV-1 to Romaine lettuce was greatest (P < 0.05) from vinyl gloves (ranging from 4.8 to 45%).  In comparison, transfer coefficient of MNV-1 from bare hands or nitrile gloves to lettuce ranged from 0.1 to 5.1% and 0.02 to 8.5%, respectively.  The transfer coefficient from lettuce was less variable (ranging from 0.22 and 11%), independent of glove type.

Significance:   This study examined virus transfer during simulated tasks involving fresh produce preparation, and indicates norovirus transfer coefficients are affected by the surfaces involved.