Reuters/Lisi Niesner
“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.
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