Shoppers told to wash their hands after visiting the supermarket to avoid bacteria on chicken wrapping that causes food poisoning Shoppers should wash their hands after leaving the supermarket thanks to dangerous bacteria lurking on millions of packs of chicken, experts say. Shoppers should wash their hands after leaving the supermarket thanks to dangerous bacteria lurking on millions of packs of chicken, experts say Safety experts say these cases could be caused by shoppers picking up the bacteria on a chicken wrapper and then feeding a child or snacking themselves.