Salad greens make the most people sick, but contaminated poultry kills the most Americans, federal researchers report in the first comprehensive look at the foods that cause foodborne illnesses. And there are a few surprises -- the bug most likely to be lurking in a salad is norovirus, and it probably came from the hands of the person who made it.

This doesn’t mean salad is more dangerous, the team at the Centers for Disease Control and Prevention stresses: It just shows what foods are most involved and may reflect how often people eat them.

“When the average American looks at this data, they need to know that we are not trying to make estimates of the risk of illness per serving of any of the food categories,” says the CDC’s  Dr. Patricia Griffin, who heads the agency’s branch that investigates stomach bugs.

“We are just providing information on what are the food categories that are the major sources of illness ... so regulators can take action to make food safer.”

Food poisoning is extremely common.  The CDC estimates that 48 million Americans get some sort of foodborne illness every year, 128,000 of them are sick enough to go to the hospital and 3,000 die. Most of the time, the bacteria, virus or parasite responsible is never identified, and usually the particular food isn’t, either.

Griffin’s team analyzed all the data they could get on every outbreak of foodborne illness reported between 1998 and 2008 in which both the food source and the microbe responsible were known. They broke the food down into 17 categories.

“We attributed 46 percent of illnesses to produce and found that more deaths were attributed to poultry than to any other commodity,” they wrote in their report, published in the journal Emerging Infectious Diseases on Tuesday.

“(The data ) indicate that efforts are particularly needed to prevent contamination of produce and poultry.”

This doesn't mean people should swap out salads for, say, fries.

“We certainly would not want people to avoid any category of food,” Griffin said. “We know that the vast majority of meals are safe. As far as fruits and vegetables in particular, CDC is well aware and promotes the fact that they are an important part of a healthy diet. They are linked to reduced risk of heart attacks, strokes and cancer. “

Cooking food is one of the best ways to prevent illness, as proper cooking will kill most disease-causing agents. As raw meat and eggs are often contaminated, proper food handling techniques are also important.

It’s harder to protect against germs on raw food, however. “Our data found that produce items were a common cause of illness, accounting for almost half of illnesses,” Griffin said in a telephone interview. “Most of those produce items that caused those illnesses were consumed raw.”

And norovirus – also known as Norwalk virus, which causes gastrointestinal upset commonly known as stomach flu or winter vomiting disease – was a major cause of illness contracted from raw vegetables, the CDC finds.

Contaminated meat and poultry accounted for 22 percent of illness but 29 percent of deaths, while dairy and eggs accounted for 20 percent of illnesses and 15 percent of deaths.

Last week, CDC reported 1,527 foodborne disease outbreaks in 2009 and 2010. They said 29,444 people got sick and 23 died in these outbreaks. Norovirus or Salmonella -- especially in eggs, sprouts, tomatoes and peppers -- caused most, while Campylobacter in unpasteurized dairy products, Salmonella in eggs, and E. coli 0157 in beef were also very common causes of food poisoning outbreaks. And nearly half -- 48 percent -- of all outbreaks from a single place were traced to restaurants or delis.

News reports have focused a great deal on outbreaks of diseases such as salmonella, listeria and E. coli, and the Food and Drug Administration, US Department of Agriculture and other regulators have focused on protecting food from animal contamination such as bird droppings and manure from pigs and cows, which carry these agents.

But norovirus is carried and spread only by humans.

“The way that you get it from food is when a food handler doesn’t wash his hands after an episode of diarrhea or vomiting and then prepares food,” Griffin said. This is an area that may require extra focus, she says.

“Washing hands is very, very important,” she added.  Norovirus can be spread before a person feels sick and for days after he or she recovers, also.

Adding to the risk is the issue of sick leave. Many food preparers, restaurant workers and food handlers do not get paid sick leave, and thus are encouraged to work while they are ill.  One study published in 2011 in the American Journal of Public Health projected that workers who did not get paid time off for illness helped spread 5 million cases of respiratory disease during the 2009 H1N1 swine flu pandemic.

The Bureau of Labor Statistics says 39 percent of private sector workers have no paid sick leave, and this number rises to 70 percent for food and hotel workers.

There’s a bill in Congress that would mandate sick leave for many employers,  supported by President Barack Obama and groups including  the National Women’s Health Network, the AFL-CIO,  Families USA and others. It was last considered in 2009.

So besides cooking meat and making sure greens are washed well, how can people protect themselves? “I would advise people to avoid eating raw foods of animal origin, and that includes raw milk,” Griffin said.  Shellfish? “You have to make a decision about raw shellfish and how much you love them, how much risk you want to take and what your risk might be,” she said.

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Paramedics dressed in protective attire enter a German cruise ship quarantined in December after an outbreak suspected to be norovirus. A new strain is making people miserable around the world this year.

It gets in your food, in your laundry, it sticks to plates and it might even float into the air when you flush your toilet. A new strain of norovirus -- often called stomach flu -- is going around and it’s going to be very hard to avoid it, experts say.

Federal health officials say a new strain, called the Sydney strain, is now causing most of the misery across the United States and the world. The virus, sometimes known as Norwalk virus or winter vomiting disease, causes vomiting, diarrhea and that someone-just-hit-me-with-a-plank feeling.

There’s no real treatment for it except for waiting it out, no vaccine, and recent studies show it’s one of the hardest viruses to get rid of. Simple cleaning alone doesn’t always kill it, and it takes just a few particles of virus to sicken a person.

“It is pretty difficult to get rid of,” says Allison Aiello, who studies how viruses spread at the University of Michigan. “It is pretty stable. It lives quite some time on surfaces. It is hard to kill.”

For instance, a few recent studies show that a quick application of hand sanitizer won’t get rid of it, Aiello says. And most people don’t wash their hands properly, either -- it takes about 30 seconds of vigorous rubbing using hot water and soap to wash away the tiny bits of virus, and that means getting under the nails, too.

Perhaps worst of all, people start spreading norovirus before they actually feel sick, and they can spread it for as long as two weeks after they start getting better. 

“Imagine you have a food handler who uses the bathroom and they haven’t washed their hands thoroughly,” Aiello said in a telephone interview. “They can end up preparing a salad for the diners that evening and end up infecting a lot of people because the food isn’t cooked. You can’t really do anything about that.”

Raw shellfish is a notorious source of norovirus and other foodborne germs, but at least one recent study suggests norovirus may be even more insidious than that. In December, a team at Ohio State University found the virus stuck to plates that had been washed in restaurant-like conditions -- and they found sticky dairy products like cheese helped the virus stay there.

Hand-washed dishes are especially likely to carry the virus, the Centers for Disease Control and Prevention says in its website -- which could be one reason norovirus causes so many outbreaks on cruise ships. “You cannot get the water hot enough if you wash by hand,” says Aiello.

Norovirus is spread fecally -- in the poop -- and that means it can get into laundry. Studies show that fecal matter spreads even in ordinary laundry, so if someone is sick, it’s important to use very hot water and bleach to destroy virus that could be on any clothing, sheets or towels.

And regular cleaner won’t get the virus off surfaces. CDC recommends using bleach, including chlorine bleach or hydrogen peroxide.

Complicating the problem, most restaurant workers don’t get paid sick leave, so if they miss work, they don’t get paid. This means many workers come in sick, and they can spread the virus to hundreds of customers. Food handlers, dishwashers, even staff who bus and clear tables, all can spread the germ.

“If they have to go back to work there has to be complete and utter vigilance about washing your hands,” Aiello says.

In June, the Food Chain Workers Alliance issued a report showing that only 21 percent of workers surveyed could take a paid sick day off work. More than half said they come to work sick because they cannot take time off.

The problem extends to the home, too. There, Aiello said, several factors make it hard to keep one sick family member from infecting others.

“It could be the door handle. It could be the toilet tank cover. Some studies show it can be aerosolized. If you throw up and then flush the toilet, how much of the spray gets into the air?” she asked. One study last year showed how the virus spread on a plastic bag that had been in a bathroom where a norovirus patient threw up. 

Norovirus is the most common cause of acute gastroenteritis -- stomach upset -- in the United States. It makes 21 million people sick every year in the United States – 70,000 on average sick enough to go to the hospital. As many as 800 people die, mostly elderly patients who become dehydrated. It’s the the most common cause of foodborne-disease outbreaks, CDC says.

Dr. John Treanor of the University of Rochester Medical Center in New York is working on a vaccine against norovirus. But the same properties that make norovirus so hard to kill also make it hard to make a vaccine.

For one thing, it’s simple. Like all viruses, norovirus hijacks live cells, turning them into virus factories that kick out particles called virions. “There is only one protein they use to make virions,” Treanor says. “If you have that one protein, it will self-assemble.”

The virus is also surrounded by a case called a capsid, which makes it hard to kill. The viruses infect the epithelial cells which line the digestive tract, causing cramps, diarrhea and vomiting, but it’s not understood exactly why.

And the virus mutates. “You typically see a specific strain, and then that strain is replaced by a new strain,” Treanor said. In this case, a strain called New Orleans has been replaced by the Sydney strain. Like with influenza, people who may have had some immunity against one strain aren’t protected agaisnt the new one.

So until there is a vaccine, what can people do? “There really isn’t very much you can do,” says Treanor. “Clearly, washing your hands is important.”

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A nasty new strain of norovirus, a highly contagious gut bug, has circled the globe and landed in the U.S., where it’s now the leading cause of what’s known indelicately as “winter vomiting disease.”

Health officials at the Centers for Disease Control and Prevention said Thursday that the GII.4 Sydney strain of norovirus was responsible for more than half of outbreaks of the illness during the last four months of 2012. The new norovirus spread amid a particularly harsh flu season that's also causing misery. 

Of 266 outbreaks of norovirus between September and December, 141 were caused by the bug that was first detected in Australia in March 2012, according to data from CaliciNet, which tracks norovirus outbreaks. The proportion of outbreaks caused by the new strain jumped dramatically from 19 percent in September to 58 percent in December, the CDC says in its weekly report on death and disease.

“Right now, it’s too soon to tell whether the new strain of norovirus will lead to more outbreaks than in previous years. However, CDC continues to work with state partners to watch this closely and see if the strain is associated with more severe illness,” said Dr. Aron Hall, a CDC epidemiologist specializing in viruses.

Like the virus that causes the flu, norovirus mutates quickly, resulting in a new strain every few years, Schaffner said. When that happens, people who’ve already had previous versions of the bug that can cause profuse vomiting and diarrhea are more likely to get it again. “What that means is more of us are susceptible,” said Dr. William Schaffner, a infectious disease expert at Vanderbilt University in Nashville, Tenn.

That can be a particular problem in enclosed spaces, such as cruise ships, nursing homes or other gatherings where people share close quarters.

The virus spreads ridiculously easily, often carried in the air after projectile vomiting, or lingering on surfaces where it infects the next victim, Schaffner said.

“It’s very contagious,” he said. “It takes only a few viral particles.”

In the U.S., norovirus is the leading cause of acute gastroenteritis, affecting more than 21 million people a year and leading to about 800 deaths, CDC said.

Though the worst part of the infection usually lasts only a few days, young children and the elderly are most at risk of serious complications, typically because of the danger of dehydration from rapid fluid loss.

Another danger is that dehydration can cause blood pressure to drop, resulting in fainting that can lead to falls. Schaffner said when he heard that U.S. Secretary of State Hillary Clinton suffered a concussion after fainting following a stomach virus in December, his first thought was norovirus.

“She’s a global traveler; she could have picked it up anywhere,” he said.

CDC officials advised health workers to be vigilant for increases in norovirus outbreaks this winter because of the new GII.4  Sydney strain. They should follow standard infection control practices to prevent norovirus.

In addition, the general public ought to be aware that the new bug is out there and take precautions including washing hands with soap and water, disinfecting surfaces, rinsing fruits and vegetables, cooking shellfish thoroughly and not preparing food or caring for others while ill.

CDC officials said it’s too early to tell whether the new strain will lead to more outbreaks or more serious illness, but they’re watching the situation closely.

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An early flu season, complicated by an aggressive strain of a stomach virus, has spread misery across the United States.

Boston’s mayor Thomas Menino declared a public health emergency and hospitals in some cities reported their already stretched emergency rooms were filling up with patients. More than 2,200 people have been hospitalized with the flu since October nationwide, according to the Centers for Disease Control and Prevention, and at least 18 children have died nationwide -- a reminder that flu can be deadly and unpredictable.

Public health officials said while the season is off to an early start, the influenza virus doesn’t so far seem to be doing anything especially unusual. They’ve been urging people since last fall to get vaccinated against the flu and to take precautions, such as frequent handwashing, to avoid infection. 

But this year, in addition to the usual colds, there's also a strain of a virulent stomach bug, called norovirus, making people sick around the world and in the United States. Patients who are sick may have a hard time telling the difference. Norovirus causes flu-like symptoms as well as vomiting and diarrhea. In the past few weeks, 250 people at a Mormon missionary training center in Provo, Utah, became sick with norovirus, the Associated Press reports. In Mill Valley Calif., two died after an outbreak of norovirus at a senior care facility over Christmas sickened 60. 

Data from the Centers for Disease Control and Prevention shows only about a third of all people with flu-like symptoms actually are testing positive for influenza. So two-thirds of the sick people have something else.

Unlike for flu, there's no vaccine for norovirus. There's also no treatment except what health professionals call supportive care – rest, fluids and ibuprofen or acetaminophen for muscle aches. Some patients with influenza can take a pill called Tamiflu. It doesn’t cure the virus but it can cut a few days off the week or so that flu usually makes people ill, if it’s taken within 48 hours of the first symptoms. 

Twenty-nine states and New York City are now reporting high levels of influenza-like-illness and more than nine states are reporting moderate levels of flu-like disease, according to the Centers for Disease Control and Prevention. 

CDC says about 8 out of every 100,000 people are being hospitalized for flu. “This is high for this time of year,” says Dr. Joe Bresee of the Centers for Disease Control and Prevention’s Influenza Division.

In a severe year, as many as 36,000 Americans die from influenza and 200,000 go into the hospital. While most who die are elderly, every year previously healthy children and young adults can also die.

“While we can’t say for certain how severe this season will be, we can say that a lot of people are getting sick with influenza and we are getting reports of severe illness and hospitalizations,” Bresee added. “Anyone who has not already been vaccinated should do so now.”

Vaccine makers have distributed 128 million doses out of about 135 million doses that they plan to make. 

The vaccine protects against three strains of the flu virus, but there’s a fourth strain circulating at low levels that is not affected by the vaccine.

CDC will update its statistics on flu Friday. It said last week that more than five percent of people seeing their doctors complained of flu-like symptoms, which is more than twice as many as this time last year. But last year was an unusually mild flu season.

“While the timing of influenza seasons also is impossible to predict, based on past experience it’s likely that flu activity will continue for some time,” the CDC cautions. Flu season usually lasts at least three months and the United States typically gets hit the worst in January and February.

Influenza-associated pediatric deaths have been reportable to CDC since the 2004-2005 season. To date, CDC has received reports of 18 pediatric deaths this season. More information about reported pediatric deaths is available at the Influenza-Associated Pediatric Mortality web application.

One factor that may indicate increased severity this season is that the predominant circulating type of influenza virus is influenza A (H3N2) viruses, which account for about 76 percent of the viruses reported. Bresee explains “typically ‘H3N2 seasons’ have been more severe, with higher numbers of hospitalizations and deaths, but we will have to see how the season plays out.”

So far this season, more than 90 percent of the influenza viruses that have been analyzed at CDC are like the viruses included in the 2012-2013 influenza vaccine. The match between the vaccine virus and circulating viruses is one factor that impacts how well the vaccine works. But Bresee cautions that other factors are involved.

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How to protect yourself from the flu? Wash your hands

Americans are getting hit with a double whammy of viruses this year – an especially vicious flu season, and on top of it, a stomach bug called norovirus that seems to be infecting more people than usual.

Both are very easy to catch and both can be very unpleasant, putting people on their backs for a week or more with fever, body aches and, in the case of norovirus, vomiting and diarrhea. Influenza also kills several thousand people every year, including previously healthy children and adults.

So how can you protect yourself? One good way is to wash your hands, wash your hands, wash your hands, experts agree.

“People need to learn to wash their hands and wash them well,” says Jeanne Matthews, chair of the department of nursing at Georgetown University School of Nursing & Health Studies in Washington, D.C. Handwashing protects you, and it keeps you from spreading any viruses you may have to anyone else.

“Certainly teaching your kids early on to wash their hands frequently is one of the most important things you can do,” Matthews adds. “Having the flu in the house doesn't have to be a family affair.”

And it can protect you even when everyone around you is sick. Viruses live in tiny droplets of saliva and mucus, which people spread when they touch their mouths or noses and then touch something else. There’s evidence that many viruses such as norovirus can really stick to plates and dishes and they definitely stick to telephones, TV remote controls, computer keyboards and other frequently touched objects.

You can pick up those germs on your own fingers, and infect yourself when you touch your nose, mouth or eyes.

Influenza can travel on tiny droplets in the air, but these sink and fall to the ground within a few feet. So teaching adults and children alike to cover their coughs can prevent the spread of all sorts of viruses, including colds and flu.

“You cough into your sleeve, or you cough into a tissue and then throw the tissue away and then wash your hands,” Matthews says.

Alcohol-based gel or foam hand sanitizers can kill viruses and bacteria, but it can be risky to rely on them alone. One study released in 2011 at the annual Meeting of the American College of Preventive Medicine found that  norovirus -- often called “stomach flu” – can spread despite their use.

Washing hands thoroughly with warm soap and water has a big advantage over hand sanitizers because it can actually wash germs down the drain.

There are two other important ways to stop the spread of viruses: vaccines, and staying home when you are sick.

“The first recommendation that we have is for everyone to get a flu shot. It’s never too early or too late to do that,” Matthews says. “Even if you have flu in your family it is a good way to protect yourself. “

And adults should stay home from work when they are sick – and keep their kids home from school when they are sick. It’s a no-brainer that too many people ignore, experts point out.

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featurepics.com

A resuable grocery bag was traced to an outbreak of norovirus that sickened members of a girls' soccer team in Oregon.

Oregon public health officials have traced a nasty outbreak of norovirus infections in a group of soccer players to an unlikely source: a reusable grocery bag contaminated with what some experts are calling “the perfect pathogens.”

The incident is raising questions, once again, about the cleanliness of the portable shopping bags that many consumers use to avoid the paper vs. plastic impact on the environment.

“We wash our clothes when they’re dirty; we should wash our bags, too,” said Kimberly K. Repp, an epidemiologist with the Washington County Department of Health and Human Services in Hillsboro, Ore. Her work is published this week in the Journal of Infectious Diseases.

Repp was an intern with the Oregon Health and Science University in October 2010 when she and other experts were asked to help unravel the mystery of sick soccer players and their chaperones. They had traveled north from Beaverton and Tigard, Ore., to Washington state on a Friday for a weekend tournament.

Less than 48 hours later, nine people were ill with unpleasant symptoms including vomiting and diarrhea. The question was: How did they get it?

One of the soccer players --  all 13- and 14-year-old girls -- had fallen ill on Saturday night and moved into the room of one of the parent chaperones. The pair went home early Sunday, with no further contact with other players.

Even so, seven other people became ill within days, stumping scientists momentarily.

CDC

Noroviruses are a group of viruses responsible for some 21 million cases of gastrointestinal illness a year, including 70,000 hospitalizations and 800 deaths.

“It involved really thinking outside the bag, so to speak,” Repp said.

Eventually, interviews revealed that most of those who became ill ate packaged cookies at a Sunday lunch. Where did the cookies come from? Turns out, the culprit was a reusable grocery bag of snacks left in the empty hotel room occupied by the first girl who got sick.

Quickly, the puzzle fell into place. The girl had been very ill in the hotel bathroom, spreading an aerosol of norovirus that landed everywhere, including on the reusable grocery bag hanging in the room.

When scientists checked the bag, it tested positive for the bug, even two weeks later.

“It was a knock out of the park,” said Repp. “We demonstrated norovirus transmission without person-to-person contact. That’s why this is different.”

The trouble with noroviruses -- which cause an estimated 21 million cases of gastroenteritis a year, some 70,000 hospitalizations and 800 deaths -- is that they’re tough bugs that can live for prolonged periods on objects and surfaces, said Dr. William Schaffner, chairman of the department of preventive medicine at Vanderbilt University Medical Center in Nashville.

“Norovirus does have the vexing capacity to persist in the environment,” he said.

While the risk of contracting an illness from any particular reusable bag is low, Schaffner said, the Oregon study follows a 2010 paper by researchers at the University of Arizona and Loma Linda University that found large numbers of bacteria in reusable grocery bags, including 12 percent that were contaminated with E. coli.

When scientists stored the bags in the trunks of cars for two hours, the number of bacteria jumped 10-fold.

Some critics dismissed that study, which was funded in part by the American Chemistry Council, which supports the makers of some disposable plastic bags.

But few have debated the study’s conclusion, which found that washing the reusable shopping bags regularly decreased contamination by 99.9 percent.

“You could just wipe it down with Lysol or Clorox,” said Repp.

Schaffner agrees. The most important tool to prevent norovirus, which spreads rapidly and infects quickly, is good hygiene, including careful hand-washing and thorough cleaning of the contaminated environment.

“You could wash the bag,” Schaffner said. “Or you could start over with a new bag."

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Sapovirus, previously regarded as rare, is showing up more often as the nasty culprit between outbreaks gastrointestinal illness in nursing homes.

For sheer misery, few germs can cause the chaos of norovirus in a nursing home.  The gut bug can spread rapidly through food, on surfaces or person-to-person, afflicting victims with violent diarrhea, vomiting and stomach pain.

About 20 million people suffer from acute norovirus infections in the U.S. each year, health officials say, but new research suggests that the nasty germ has an equally cruddy but little-known cousin: sapovirus.

Health researchers in Oregon and Minnesota have discovered that once-rare sapovirus may be more common than thought and, worse, on the rise, particularly in nursing homes and long-term care centers.

“It’s an up-and-coming bug,” said Lore Elizabeth Lee, an Oregon public health epidemiologist and author of a new study on sapovirus in the journal Emerging Infectious Diseases.

A review of2,161 gastrointestinal outbreaks in the two states yielded some surprising results. Sure, more than half of the outbreaks were caused by norovirus, and nearly a quarter were caused by bacteria, parasites or other agents, as expected.

But among 142 non-norovirus outbreaks that remained a mystery, scientists tested samples from 93 and found that nearly a quarter were caused by the new culprit,sapovirus, Lee said.

“It means we have another virus circulating that we need to study,” she explained.

The virus operates about the same as norovirus, mostly causing diarrhea, vomiting and, in some cases, fever. It appears to spread in the same ways: person-to-person, on surfaces and through food.

Of the 21 sapovirus outbreaks detected by Lee and her colleagues, 66 percent occurred in long-term care centers, another 10 percent occurred in schools and the rest occurred in familiar norovirus venues: a prison, a large psychiatric hospital, a restaurant and a cruise ship.

That means that sapovirus, once regarded as a sporadic illness in children, may be spreading its gastrointestinal misery in a similar pattern as norovirus, including in nursing homes and beyond. “It’s probably circulating in a lot of other settings as well,” Lee said.

Part of the same family of Caliciviridae viruses, norovirus and sapovirus are separate bugs. Sapovirus was first detected in 1977 at a home for infants in Sapporo, Japan, where it got its name.

It appeared mostly to lie low for a quarter-century, until 2002, when scientists developed a new test for the virus and suddenly found it showing up in more places. “The reason we’re seeing it now is we’re actively testing for it,” Lee said.

All of that is important because of the potential harm of a gut bug like this. Norovirus is the leading cause of foodborne disease outbreaks in the United States, and a similar bug could be responsible for more of those illnesses as well.

In most people, it’s a miserable but brief bout. But in children, the elderly or people with weakened immune systems, it can lead to hospitalization or even death.

Being able to identify the virus behind disabling outbreaks is important, Lee said.

Minnesota is testing for sapovirus and Oregon will soon begin, Lee said, with other states following in the future, perhaps.

In the meantime, the same steps that prevent norovirus will knock down sapovirus as well. That means good hand hygiene, careful food preparation and scrupulous attention to environmental cleanliness.

“Bleach,” said Lee. “Strong bleach.”

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By Msnbc.com staff and wire

Nearly 200 people reported getting sick after attending the Salute to Spirit and State Cheerleading Championships at the Comcast Arena in Everett, Wash., last weekend, according to KING 5 News.

Washington state health officials said they were investigating and that people who'd attended the weekend high school cheerleading competition began reporting vomiting or diarrhea on Sunday and Monday.

"At least 19 squads are reporting high numbers of illnesses," Kate Lynch, a spokeswoman for the Washington State Department of Health, told Reuters. She said 1,200 cheerleaders from 45 high schools participated in the event about 30 miles northeast of Seattle.

Health officials said they learned of the outbreak, which has flu-like symptoms similar to those found in the illnesses norovirus, rotavirus or a food-borne illness, on Tuesday.

More than 3,000 people attended the event, the Washington Interscholastic Activities Association said in a statement. "Our immediate concerns are for those who have been affected by this illness and our thoughts are with them," Mike Colbrese, the association's executive director, said in a statement.

Cheerleaders at Seattle's Ballard High School said nearly half their squad became sick.

Ballard cheerleader Summer Gnoinski told KING 5, "I threw up every hour on the hour." Her sister, Karly, who did not get sick, calls herself "one of the lucky ones."

Assistant cheerleading coach Michelle Whelan says until they know what's going on, she's taking extra precautions. "I'm not letting the girls use pom-poms, signs, flags or anything else that was at the competition until we can disinfect them."

Updated Feb. 12, 9 a.m. EST: Crown Princess departed Port Everglades Saturday afternoon after a two-day intensive cleaning. According to Princess, 226 passengers (7.34 percent out of 3,078) and 63 crew (5.35 percent of 1,178) reported gastrointestinal illness during the shortened cruise.

Crown Princess will end its current cruise two days early following a spike in cases of gastrointestinal illness for the second straight week.

In a statement, Princess Cruises said the 113,000-ton, 3,080-passenger ship will return to its Fort Lauderdale, Fla., homeport on Thursday instead of Saturday, where it will undergo two days of sanitization in consultation with the U.S. Centers for Disease Control and Prevention (CDC).

Impacted passengers will receive full refunds for the cruise, flights home, coverage of change fees if air was not booked through Princess, hotel accommodation if necessary and a 25 percent future cruise credit.

A total of 364 of 3,103 passengers and 30 of 1,168 crew were infected on last week's cruise, after which Princess undertook what it describes as "rigorous sanitization measures ... [including] a comprehensive disinfection of all cabins and public areas." The sanitization, which delayed the ship's Feb. 4 departure by some six hours, was overseen by the CDC together with the line's public health, medical and onboard departments.

Norovirus is the second most common illness next to the common cold, and is highly contagious, spreading easily in confined spaces such as hospitals, hotels, dormitories and cruise ships. Symptoms include vomiting and diarrhea, and millions are infected each year.

Cruise lines participating in the CDC's Vessel Sanitation Program -- and every major operator does -- are required to report the total number of G.I. cases evaluated by the medical staff before the ship arrives at a U.S. port when sailing from a foreign port. A separate notification is required when the count exceeds 2 percent of the total number of passengers or crew onboard.

The Crown Princess will return to port two days early after 114 passengers on the latest voyage have reported gastrointestinal illness.

Princess said the upcoming two-day disinfection will include "bringing aboard additional cleaning crew to assist with a thorough sanitization of all public spaces and surfaces including soft furnishing and carpets, railings, door handles and the like. Additionally, once all of the passengers have disembarked on Thursday morning, all bed linens and towels will be removed from every stateroom. The staterooms will be sanitized multiple times before making up the rooms with fresh linens and towels on Saturday morning, just prior to passenger embarkation."

The line said it expects the next cruise to depart on Feb. 11 as scheduled.

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