Oysters can contain harmful bacteria. Oysters are filter feeders, so will naturally concentrate anything present in the surrounding water. Oysters from the Gulf Coast of the United States, for example, contain high bacterial loads of human pathogens in the warm months, most notably "Vibrio vulnificus" and "Vibrio parahaemolyticus". In these cases, the main danger is for immunocompromised individuals, who are unable to fight off infection and can succumb to sepsis, leading to death. "Vibrio vulnificus" is the most deadly seafood-borne pathogen.