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Could Britain's major norovirus outbreak spread to the US?

Robin Wulffson MD's picture
norovirus, gastroenteritis, England, cruise ship, prevention, treatment

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). The report notes that the latest figures are 72% higher than the number of cases reported at this point last year (2,255 cases). The report falls on the heels of a Centers for Disease Control and Prevention (CDC) report released last week of norovirus outbreaks on two large cruise ships currently sailing in the Caribbean: the Queen Mary 2 and the Emerald Princess. Interestingly, the Queen Mary 2 primarily makes a transatlantic crossing between Southampton, England and New York.

The HPA notes that during the Christmas period there is typically a drop in the number of laboratory reports. In previous norovirus seasons the general trend is that cases increase in the New Year; thus, the agency predicts that cases will increase over the next few weeks. In addition, during the two weeks up to December 30, 29 hospital outbreaks were reported, compared to 70 in the previous two weeks, bringing the total of outbreaks for the season to 590.

In addition to the surge in cases in England, the HPA notes that cases have increased throughout Europe, Japan, Australia, and elsewhere around the globe. To date, the agency has no explanation for the uptick; however, it notes that case number and activity varies significantly from year to year. In Australia the norovirus season also peaks during the winter; however, this season it has gone on longer than usual and they are seeing cases into their summer. The HPA notes that the number of laboratory confirmed cases represents just a fraction of the actual amount of norovirus activity as it is estimated that for each confirmed case, there are a further 288 unreported cases because the vast majority of those affected do not seek healthcare services in response to their illness.

Norovirus can be transmitted by contact with contaminated surfaces or objects, by contact with an infected person, or by the consumption of contaminated food or water. Symptoms include a sudden onset of vomiting, which can be projectile, and diarrhea, which may be profuse and watery. Some victims also suffer fevers, headaches and stomach cramps. Although most cases resolve in a matter of days, approximately 800 people die from an infection each year, according to the Centers for Disease Control and Prevention (CDC). John Harris, a HPA norovirus expert from the HPA, noted, “Norovirus is very contagious, and anyone who has had it knows it is very unpleasant. If you think you may have the illness then it is important to maintain good hand hygiene to help prevent it spreading. We also advise that people stay away from hospitals, schools and care homes as these environments are particularly prone to outbreaks.”

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The two latest cruise ship outbreaks, which are most likely due to the norovirus, occurred on two large cruise ships. Last week, 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. A major factor of rapid norovirus outbreaks on cruise ships is because the virus can quickly spread in contained, crowded places. Other locations at increased risk are long-term care facilities, daycare centers, schools, and hotels. Noroviruses can also be a major cause of gastroenteritis in restaurants and catered-meal settings if contaminated food is served.

The recent cruise ship norovirus outbreaks, coupled with the major upsurge of cases in England and other parts of the globe indicates that a significant increase in norovirus infections is likely to occur in the United States. Many of the cruise ship passengers are Americans and will return to various locations in the US and may be contagious. Beyond cruise ships, frequent flights between the US and England, as well as other areas of the globe with a norovirus uptick, increase the risk of spread. 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.

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).

Reference: Britain’s Health Protection Agency (HPA)

See also: Don't let the norovirus ruin your next cruise or vacation