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Mutant norovirus strain triggers concern of US health officials

Robin Wulffson MD's picture
norovirus, mutant strain, outbreak, prevention, Salt Lake City

A new strain of norovirus that first appeared in Australia last September has now crossed the Pacific Ocean and is wreaking havoc in Salt Lake City. Its appearance in Utah, coupled with two recent outbreaks on cruise ships carrying passengers from the US indicates that norovirus infections are very likely to increase in other parts of the US. Norovirus is an organism that is capable of rapidly mutating to a new strain; thus, individuals with a previous infection are susceptible to reinfection when a new strain emerges. Most infected individuals suffer from nausea, vomiting, and diarrhea for a few days; however, infections can be serious, sometimes resulting in death in seniors, children, and individuals with immunodeficiency.

The new mutant strain has been dubbed Genotype II.4 or “Sydney 2012.” In Australia the norovirus season usually peaks during their winter; however, this season it has gone on longer than usual and they are seeing cases into their summer, which is winter in the United States. Other areas of the globe have also experienced an upsurge in norovirus outbreaks. According to a report released on January 2 by Britain’s Health Protection Agency (HPA), 3,877 laboratory confirmed cases of norovirus have occurred in the nation this season (from week 27 to week 51 2012). In addition to the surge in cases in England and Australia, the HPA notes that cases have increased throughout Europe, Japan, and elsewhere around the globe. Contributing to the spread of the virus is air travel. Air travel encompasses close contact with other passengers as well as breathing recirculated air—a happy hunting ground for the norovirus. An infected airline passenger will return home while ill or still contagious; thus, posing a risk to family and friends.

Currently, Salt Lake Valley Health Department is investigating multiple “clusters” of the disease throughout the valley. The agency is paying particular attention to nursing homes, which it notes are often the hardest hit due to close living quarters and the time of the year. “It’s very fast-moving and very contagious,” noted Salt Lake Valley Health Department epidemiologist Jennifer Robertson. She explained that the illness is spread when someone comes in contact with an infected person, such as a caregiver, or when someone ingests food or water that has been contaminated with the virus or has touched the same surface as someone with the virus. It spreads easily, especially in closed settings. She noted that norovirus infections are most common at this time of the year and that a new strain seems to surface every two or three years, as immunity to other strains increases and random genetic mutations arise.

The highly contagious organism is believed to have sickened approximately 250 missionaries at The Church of Jesus Christ of Latter-day Saints’ Missionary Training Center in Provo recently. The virus spread rapidly through the facility; however, precautions are ongoing in an attempt to prevent further spread of illness, including encouragement of proper hand-washing techniques. The actual number of norovirus in Utah is unknown because, with all outbreaks of the virus, many cases go unreported.

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According to the Centers for Disease Control and Prevention (CDC), cruise ships, schools, hospitals, restaurants and other gathering places have borne the brunt of the illness in its recent spread, as large numbers of people are confined to a smaller space. In late December, the CDC has reported that two norovirus outbreaks have occurred on two cruise ships. An outbreak sickened 194 passengers and 11 crew members aboard the Cunard Line luxury cruise ship Queen Mary 2. That same week, 189 passengers and 31 crew members aboard the Emerald Princess, operated by Princess Cruise Lines, came down with symptoms attributed to the norovirus.

The virus is present in the vomit and stool of infected individuals. It can be acquired by:

  • Eating food or drinking liquids that are contaminated with norovirus (someone gets stool or vomit on their hands; then touches food or drink).
  • Touching surfaces or objects contaminated with norovirus and then putting your hand or fingers in your mouth.
  • Having direct contact with a person who is infected with norovirus (for example, when caring for someone with norovirus or sharing foods or eating utensils with them).

People with norovirus illness are contagious from the moment they begin feeling sick until at least three days after they recover. However, some people may be contagious for even longer. Currently, there is no vaccine or treatment for the infection beyond supportive measures such as anti-nausea medication, anti-diarrheal medicine, and fluids.

Salt Lake Valley Health Department

See also:
Could Britain's major norovirus outbreak spread to the US?
Don't let the norovirus ruin your next cruise or vacation