Janitors and cleaners (except maids and housekeeping cleaners) perform a range of duties from cleaning floors to taking out the garbage to painting and carpentry.

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Unilever sells a vast range of brands, including Cif cleaning products, PG Tips tea, Hellman's mayonnaise, Dove soap and Vaseline.

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"We can't say for sure how much of that benefit is down to the yoghurt and how much they are down to a whole range of infection control procedures that the hospital has in place such as the deep cleaning programme, the bare-below-the-elbow programme, and the increased isolation procedures, " Ms Heyes said.

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