Norovirus

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Foodborne illness is common in the U.S. The Centers for Disease Control, or CDC, estimates that there are 48 million cases of foodborne illness each year in the U.S., with 128,000 hospitalizations and 3,000 deaths. The five most common causes of foodborne illness are norovirus, salmonella, clostridium perfringens, campylobacter, and staphylococcus aureus. All are caused by contact with an infected person, an infected food or surface, or consumption of infected food or liquid. Together, these diseases are commonly called, “food poisoning,” a “stomach flu,” or a “stomach bug.” Hospitalization is often needed due to dehydration and the very young and very old are most susceptible. Death may be caused by dehydration or kidney failure, shock, or vascular collapse from toxins related to the infection. This is especially true with staph aureus infections. As norovirus is the most common foodborne illness, I would like to discuss it today.

Norovirus is often referred to as the “cruise ship virus,” however cruise ship outbreaks are responsible for only 1% of cases. Norovirus is unrelated to the influenza virus which causes the flu. Outbreaks are typically seen from November to April but can be seen at any time of the year. Symptoms include diarrhea, nausea and vomiting, and abdominal pain. Other symptoms may include fever, muscle aches, and headache. Like most foodborne illnesses, norovirus cases are most frequently seen in food service areas like restaurants, cafeterias, and catered events, healthcare facilities, schools and childcare facilities, summer camps, and cruise ships. Norovirus is highly contagious. If food is prepared by an infected person, merely touching that food, for example raw fruit, and then putting your hands in your mouth or on your lips will transmit the virus to you. Likewise, consuming contaminated food or drink will transmit the virus, as will touching a surface that a contaminated person touched (i.e. doorknobs). Symptoms usually start 12 to 48 hours after exposure and typically last one to three days. There is no treatment for norovirus. Antibiotics are ineffective. The mainstay of treatment is hydration.

Preventing transmission of the virus is important in reducing the number of cases. If you are infected, do not prepare food for anyone for at least two days after symptoms subside. If someone in your house becomes infected, avoid direct contact with that person, wash your hands thoroughly and frequently with soap and warm water (alcohol-based hand sanitizers are less effective at killing the virus), and wash your clothes and the clothes of the infected person in hot water. Clean all surfaces with a chlorine bleach-containing solution or a disinfectant that is certified effective against norovirus, especially if an infected person vomited or had diarrhea on it.

To avoid being infected in areas where norovirus is common, like summer camps and cruise ships, there are a few rules of thumb to follow. First, wash your hands frequently, especially after touching common areas like doorknobs and tables. If you see someone vomiting or having diarrhea, leave the area immediately (the virus may be aerosolized by vomiting). Do not share food or utensils and avoid direct personal contact (like handshakes). Avoid putting your hands in or near your mouth. Lastly, as there are many forms of norovirus, having had the virus does not provide immunity to being infected again.

For more information, go to: www.cdc.gov/norovirus/index.html  

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 By Peter Galvin, MD

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