A British woman was recently sickened with norovirus from oysters, although she hadn’t eaten any. It turns out that she got the infection from a friend who got it from eating the oysters. Natalie Dye, 49, of Esher, Surrey, reportedly dined at a restaurant with friends after a seaside holiday and consciously avoided eating any oysters, the specialty of the house. “I am careful with anything raw or undercooked because I hate being ill, so I didn’t have one,” she said. When her friend who had eaten the oysters became ill within 24 hours with vomiting and diarrhea, Dye felt sorry for him but was glad she hadn’t had any. However, she became ill two days later with the same symptoms as her friend. “I was hot then cold, I ached all over, then I started vomiting uncontrollably. I was bedridden for two days and weak and ill for a week. My husband called the GP and we were amazed when he told us that Richard’s oyster was almost certainly the cause,” Dye said. She speculated that she might have caught the norovirus when she helped take care of her friend, sat with him in the car, or hugged him goodbye. “I simply didn’t realize his food poisoning was contagious,” she said. A two-year study in the U.K. revealed in 2011 that 75 percent of British-raised oysters contain norovirus, according to BBC News. The virus is estimated to affect as many as 1 million people there every year. The study, by the U.K. Food Standards Agency, did not change the agency’s public health warnings. FSA still advises people that eating raw oysters is a food safety risk, and that older people, pregnant women, young children and those with health problems should not eat raw oysters or other raw shellfish. However, because norovirus is so contagious, a person can get it even without eating the problematic food item but just by being around someone who already has the virus from that food source. A University of Southampton microbiologist, Dr. Ian Clarke, said that oysters are a common source of foodborne outbreaks. “It can start by one person eating a norovirus-contaminated oyster and then passing the virus on by person-to-person contact,” he noted. Researchers recently found that oysters allow viruses to live, grow, and produce more virulent strains. The norovirus, like cold and flu viruses, can mutate, and therefore new strains can cause outbreaks in those with no immunity to them. The research team, headed by Professor Yongjie Wang from Shanghai Ocean University, analyzed the genetic material of more than 1,000 norovirus samples taken from oysters and found that more than 80 percent of the known human norovirus strains were in oysters. In addition, new strains found in oysters matched those in new outbreaks in humans, and 90 percent of norovirus outbreaks could be traced to coastal regions, according to the research. The reason why not everyone gets sick when they eat an oyster is because many of the norovirus-contaminated bivalves contain the virus at such a low level that it doesn’t affect people, Clarke said.

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