Professor Gerba is known as “Dr Germ” because of the number of studies he has done on bacteria and everyday objects. His previous studies warned of bacteria on reusable shopping bags, airplane seat-back trays, ground-floor elevator buttons, water fountain toggles, computer keyboards, iPads and playground equipment. He said just about anything touched by children has a high chance of contamination. He advised people to wash reusable shopping bags after use, otherwise they’ll become full of “bacterial swamps”. He added: “It’s like wearing the same underwear every day.” Gerba said the best way to avoid getting sick from shopping trolleys is to wipe the handle with a disinfectant cloth and wash your hands often.