Poor Larry isn't looking too good. He's pale and clammy and he's been projectile vomiting over and over again while his carers just stand by and watch.

Yet their lack of concern for Larry is made up for by their intense interest in how far splashes of his vomit can fly, and how effectively they evade attempts to clean them up.

Larry is a "humanoid simulated vomiting system" designed to help scientists analyze contagion. And like millions around the world right now, he's struggling with norovirus - a disease one British expert describes as "the Ferrari of the virus world".

"Norovirus is one of the most infectious viruses of man," said Ian Goodfellow, a professor of virology at the department of pathology at Britain's University of Cambridge, who has been studying noroviruses for 10 years.

"It takes fewer than 20 virus particles to infect someone. So each droplet of vomit or gram of feces from an infected person can contain enough virus to infect more than 100,000 people."

Norovirus is hitting hard this year - and earlier too.

In Britain so far this season, more than a million people are thought to have suffered the violent vomiting and diarrhea it can bring. The Health Protection Agency (HPA) said this high rate of infection relatively early in the winter mirrors trends seen in Japan and Europe.

"In Australia the norovirus season also peaks during the winter, but this season it has gone on longer than usual and they are seeing cases into their summer," it said in a statement.

In the United States, the Centers for Disease Control and Prevention (CDC) say norovirus causes 21 million illnesses annually. Of those who get the virus, some 70,000 require hospitalization and around 800 die each year. 

Profuse and projectile 

Norovirus dates back more than 40 years and takes its name from the U.S. city of Norwalk, Ohio, where there was an outbreak of acute gastroenteritis in school children in November 1968.

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.

John Harris, an expert on the virus at Britain's HPA, puts it simply: "Norovirus is very contagious and very unpleasant."

What makes this such a formidable enemy is its ability to evade death from cleaning and to survive long periods outside a human host. Scientists have found norovirus can remain alive and well for 12 hours on hard surfaces and up to 12 days on contaminated fabrics such as carpets and upholstery. In still water, it can survive for months, maybe even years.

At the Health and Safety Laboratory in Derbyshire, northern England, where researcher Catherine Makison developed the humanoid simulated vomiting system and nicknamed him "Vomiting Larry", scientists analyzing his reach found that small droplets of sick can spread over three meters.

"The dramatic nature of the vomiting episodes produces a lot of aerosolized vomit, much of which is invisible to the naked eye," Goodfellow told Reuters.

Larry's projections were easy to spot because he had been primed with a "vomitus substitute", scientists explain, which included a fluorescent marker to help distinguish even small splashes - but they would not be at all easily visible under standard white hospital lighting.

Add the fact that norovirus is particularly resistant to normal household disinfectants and even alcohol hand gels, and it's little wonder the sickness wreaks such havoc in hospitals, schools, nursing homes, cruise ships and hotels.

During the two weeks up to December 23, there were 70 hospital outbreaks of norovirus reported in Britain, and last week a cruise ship that sails between New York and Britain's Southampton docked in the Caribbean with about 200 people on board suffering suspected norovirus.

Moving target

The good news, for some, is that not everyone appears to be equally susceptible to norovirus infection. According to Goodfellow, around 20 percent of Europeans have a mutation in a gene called FUT2 that makes them resistant.

For the rest the only likely good news will have to wait for the results of trials of a potential norovirus vaccine developed by U.S. drugmaker LigoCyte Pharmaceuticals Inc, or from one of several research teams around the world working on possible new antiviral drugs to treat the infection.

Early tests in 2011 indicated that around half of people vaccinated with the experimental shot, now owned by Japan's Takeda Pharmaceutical Co, were protected from symptomatic norovirus infection.

The bad news, virologists say, is that the virus changes constantly, making it a moving target for drug developers. There is also evidence that humans' immune response to infection is short-lived, so people can become re-infected by the same virus within just a year or two.

"There are many strains, and the virus changes very rapidly - it undergoes something virologists call genetic drift," Harris said in a telephone interview. "When it makes copies of itself, it makes mistakes in those copies - so each time you encounter the virus you may be encountering a slightly different one."

This means that even if a vaccine were to be fully developed - still a big 'if' - it would probably need to be tweaked and repeated in a slightly different formula each year to prevent people getting sick.

Until any effective drugs or vaccines are developed, experts reckon that like the common cold, norovirus will be an unwelcome guest for many winters to come. Their advice is to stay away from anyone with the virus, and use soap and water liberally.

"One of the reasons norovirus spreads so fast is that the majority of people don't wash their hands for long enough," said Goodfellow. "We'd suggest people count to 15 while washing their hands and ensure their hands are dried completely."

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