Micro bubbles have also been introduced by the Japanese to market safe and good tasting oysters. Micro bubbles of concentrated oxygen containing about 2% ozone can be used to inactivate norovirus in shellfish and oysters. This norovirus is one of the major pathogens causing food poisoning in winter. This is a much more cost effective method compared to cultivating the oysters in sterile seawater and using chlorine-based germicide.