The US Food and Drug Administration (FDA), federal and state health authorities, along with Canadian public health officials, are investigating multi-province and multi-state norovirus outbreaks linked to raw oysters from British Columbia. Currently, there is no word on how many illnesses and states are involved in the US part of the outbreak; however, potentially contaminated raw oysters harvested in the south and central parts of Baynes Sound, British Columbia, Canada, were distributed to California, Illinois, Massachusetts, New York, and Washington. It is possible that additional states received these oysters either directly from Canada or through further distribution within the U.S.
According to the Public Health Agency of Canada (PHAC), 172 cases so far have been reported in three provinces — British Columbia, Alberta, and Ontario. The US Centers for Disease Control and Prevention (CDC) said contaminated oysters and other shellfish are common causes of norovirus outbreaks and therefore, it recommends cooking oysters and other shellfish thoroughly (to 145°F or higher) before eating.
Norovirus is the most common cause of acute gastroenteritis (AGE), resulting in roughly 1 in 5 cases worldwide, across all settings and age groups — it’s well-known for causing outbreaks where people share close quarters, such as during conventions, at the Olympics, and on cruise ships.
The virus was a prominent headliner at the recently concluded Winter Olympics in Pyeong Chang, South Korea. Last year at the World Athletics Championships in London, the virus rapidly spread through one hotel, and several athletes withdrew from events after suffering symptoms including vomiting. Norovirus is the same bug that caused hundreds of illnesses at Chipotle restaurants in 2015 and 2017. In 2017, the CDC recorded nine norovirus outbreaks on cruise ships that affected hundreds of people.
Norovirus causes 19 to 21 million illnesses, 400,000 emergency room visits, and 570 to 800 deaths, mostly in young children and the elderly, each year in the United States alone. Norovirus kills over 200,000 annually and can be a significant economic drain to societies where outbreaks of the virus are frequent. Globally, it is estimated to cost approximately $4.2 billion in health care costs and over $60 billion in societal costs. According to the US Department of Agriculture, which monitors foodborne illnesses, norovirus is five times as deadly and eight times as costly as the E. coli virus. These cost estimates are conservative as many norovirus cases go unreported. In contrast, rotavirus, a diarrheal disease that kills babies but rarely endangers patients over the age of five, was estimated to cost $2 billion annually before a vaccine was made.
Norovirus sheds from the feces of infected people and animals, and just 10 viral particles are enough to cause an infection. Norovirus can cling to hard surfaces and people can become sick from eating contaminated food or drinking contaminated water. The virus affects members from all age groups and is usually characterized by inflammation of the stomach, diarrhea, and vomiting. There are different methods to treat the infection and correct diagnosis will, in most cases, lead to a full recovery. However, despite the majority of people recovering after a few days of discomfort, the virus has the potential to be highly fatal, especially to young children and the elderly.
There is currently no specific medication or vaccine for norovirus infection, although several vaccine strategies, mostly using virus-like particle antigens (VLPs), are in development and have shown proof of efficacy, the most advanced being the adjuvanted bivalent intramuscular norovirus virus-like particle (VLP) vaccine. Without a vaccine, the single best way to avoid infection is to practice good handwashing habits, especially after using the restroom and before eating. Rigorous handwashing before eating or touching the face could theoretically reduce the size of the outbreak by 100 percent