Norovirus Notebook: Winter Vomiting Bug Takes Summer Cruise

July 10, 2009

In spite of its nickname – the Winter Vomiting Bug – Norovirus can be counted upon to pop up at any time of year, especially where large numbers of people are confined together.

On July 6, BBC reported that as many as 150 people out of 769 passengers and 340 crew members on board the Transocean Tours cruise ship, the Marco Polo were ill with a suspected outbreak of Norovirus. By July 9th, the outbreak of this highly infectious virus had spread to as many as 400 people, seven of whom required hospital treatment.

While the Marco Polo outbreak was unusual in its size (nearly 40% of the ship's population may have been infected), Norovirus outbreaks are one of the most common causes of shipboard illness. The US Centers for Disease Control and Prevention (CDC) require ship operators traveling between foreign and US ports to report any cases of gastrointestinal illness before docking. Operators must make a separate notification when more than 2% of a ship's population (passengers and crew) is affected. Year after year, Norovirus accounts for well more than 50% of the cruise ship outbreaks for which a precise cause is identified.

Cruise ships, though, are just one venue that encourages the spread of Norovirus. It also thrives in hospitals, nursing homes, day care centers, and schools. It can be waterborne, or foodborne, or the virus can be spread hand-to-mouth. Norovirus, for the first time, was the leading reported cause of foodborne illness in the United States in 2006.

At the moment, there is no recognized antiviral treatment for Norovirus gastroenteritis, and no vaccine available. But that situation may be changing. Researchers at the Sahlgrenska Academy, University of Gothenburg, Sweden have learned how the virus attaches to human cells – the first step in infection.

The discovery may lead to development of a drug that would block the attachment sites on the cells, making it impossible for the virus to establish a foothold in its intended victim. The effectiveness of the drug would likely be short-lived. It could, however, be offered to individuals who are about to embark on a cruise and provide protection for the duration of that cruise.

The development of this drug is still nothing more than a gleam in the research team's eyes. It may never come to pass. At best, it will be several years before anything is available for testing – much less for routine use.

In the meantime, the only protection against contracting a Norovirus infection is scrupulous attention to personal hygiene, avoidance of high-risk food venues (such as buffets), and frequent hand-washing.

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