A new strain of a vomiting bug first found in Australia has killed nursing home residents from California to Japan, spoiled luxury cruises and may have sickened more than 1 million Britons so far in its global sweep.
The new norovirus, identified in Sydney last March, caused the worst bout of gastroenteritis in a decade in Australia’s Victoria state last year. Health-care facilities in the Northern Hemisphere should prepare for a “severe” epidemic this winter, researchers from eight countries said in a report this month.
The norovirus strain is adding to a list of winter ails topped by a resurgence of flu. Gastro outbreaks have been reported in New Zealand, France, Belgium, Denmark and Scotland, and cruise ships carrying suspected patients have docked in New York and Florida the past three weeks, heralding a new wave of infections for which there is no specific treatment or vaccine.
“Cruise ships are almost a sentinel sensing system for norovirus,” said Peter White, professor of microbiology at the University of New South Wales in Sydney, who helped identify and characterize the new strain. “Norovirus is going to wreak havoc in their cruise industry for the next year while this new strain gets a grip.”
Carnival Corp.’s 14-deck Queen Mary 2 sailed into Brooklyn Jan. 3 after 204 passengers and 16 crew came down with suspected norovirus. A week earlier, Carnival’s Emerald Princess arrived in Fort Lauderdale after 189 passengers and 31 crew had developed the same symptoms, the Centers for Disease Control and Prevention said.
An official at Miami-based Carnival referred questions on norovirus, sometimes known as winter vomiting bug, to Cruise Lines International Association, an industry group.
“Historic incidence rates of gastrointestinal illness aboard cruise ships are low,” said David Peikin, the association’s director of public affairs. “One of the cruise industries’ top priorities is preventing gastrointestinal illness from being brought on board a ship.”
Shares of Carnival, the world’s biggest cruise-line operator, gained less than 1 percent to $37.65 at the close yesterday in New York and have increased 2.4 percent since Jan. 1. Miami-based Royal Caribbean Cruises Ltd., the world’s second-largest cruise operator, added less than 1 percent to $36.20 and has rallied 6.5 percent this year.
While long-term care facilities and schools are especially prone to outbreaks, new epidemics of acute gastro often emerge on cruise ships, where control is hindered by close living quarters and shared dining areas. With regular turnover of passengers, noroviruses on ships can repeatedly infect new susceptible travelers, researchers at the Center for Infectious Disease Control in Bilthoven, Netherlands, found in a 2008 study.
“Cruise ship holidays create an environment in which norovirus is easily spread and outbreaks readily occur,” the authors said, noting that a reporting system for cruise ship-related outbreaks’’ may provide an early warning system for winter epidemics in the wider community.
Exhaustive control measures may not always be sufficient to eliminate the virus, the researchers said. Norovirus can persist on surfaces and is resistant to many common disinfectants, according to the Atlanta-based CDC. It estimates more than 90 percent of diarrheal disease outbreaks on cruise ships are caused by norovirus.
“It’s almost impossible for them to protect themselves against a norovirus outbreak once it occurs,” White said. “The only way you could do it would be to stay in your cabin the whole time and not go out.”
Norovirus is the most common cause of acute gastroenteritis in the U.S, causing about 21 million illnesses, 70,000 hospitalizations and 800 deaths a year, according to the CDC.
Symptoms of norovirus include a sudden onset of vomiting and, or diarrhea. Some people may have a temperature, headache and stomach cramps. The illness usually resolves in one or two days and there are no long-term effects.
Outbreaks occur throughout the year, peaking in January and February. In the U.K., the bug hospitalizes 3,000 people a year and costs the National Health Service more than 100 million pounds ($160 million).
There have been 4,407 laboratory-confirmed cases of norovirus so far this season -- 56 percent more than reported a year ago, the U.K.’s Health Protection Agency said yesterday in a statement. About 1.2 million people in England and Wales may have caught the bug.
Salt Lake County
In Salt Lake County, Utah, norovirus is suspected to have sickened about 1,000 people in eight clusters in the six weeks through Jan. 10, compared with two clusters of cases usually for that time of the year, said Ilene Risk, the county’s epidemiology director, in an e-mail.
The disease can be severe, especially for the very young, the elderly, and those with weakened immune systems, said Bill Rawlinson, senior medical virologist and director of virology at South Eastern Sydney and Illawarra Area Health Service.
Immunocompromised patients can excrete the virus for many weeks at low levels. Complications arise when infected people aren’t adequately rehydrated, he said.
Two residents of a senior care center in Mill Valley, California, died in an outbreak that sickened dozens of people. Japan has recorded 123 outbreaks in 17 prefectures linked to restaurants, hospitals, banquet facilities, nursing homes and hotels since September, according to the National Institute of Infectious Diseases. At least 10 people died from suspected infections.
The Sydney variant is the result of a combination of two different strains, according to White, the microbiology professor. It also mutated slightly from its closest relatives, ensuring nobody is immune to it.
“The immunity that people carry from previous norovirus infections won’t protect them from this new virus,” White said. “Therefore, the virus can infect many more people.”
The new strain doesn’t cause more serious illness than others, and strategies for managing outbreaks are the same for any norovirus, the U.K.’s Health Protection Agency said. These measures include washing the hands thoroughly and regularly, particularly after using the toilet and before eating.
“Noroviruses mutate rapidly and new strains are constantly emerging,” said David Brown, director of the HPA’s virology reference department, in a Jan. 9 statement. “There is no specific treatment for norovirus infection other than to let the illness take its course, with symptoms usually lasting around two days. Keeping hydrated is very important and you can take over-the-counter medicines to relieve headaches and aches and pains.”
The best way to stem its spread is to practice good hand hygiene and for sufferers to avoid contact with other people, including staying home from work and not returning for two days once symptoms have subsided, said White.
“This virus will definitely lead to large increases in gastroenteritis across the globe for the next year,” he said.