Is%20the%20common%20cold%20becoming%20a%20killer - Is the...

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Is the common cold becoming a killer? 03 September 2008 From New Scientist Print Edition. Subscribe and get 4 free issues. Debora MacKenzie IN APRIL last year, Paige Villers was finishing basic training at Lackland Air Force Base in Texas when she came down with a cold. She struggled to shake it off. Then came a prolonged battle with pneumonia, followed by an immune over-reaction that killed her. "She had symptoms that just looked like a cold or the flu," Villers's mother told reporters. "You hear of people dying of pneumonia, but it's usually older people. Not a 19-year-old in the prime of her life." It turned out that Villers had been infected by an adenovirus, a family of viruses that normally causes no more than a common cold. But this virus was a nasty new strain called Ad14, which killed at least 140 people in the US in 2007. The real toll may well have be much higher, as the viruses behind such deaths are rarely diagnosed. The emergence of Ad14 - and the surprising turn it took this year - is a sharp reminder that a harmless cold is not the only possible outcome of the constant battle between people and respiratory viruses. There can be others. Even before the discovery of Ad14, interest in cold viruses had revived, partly thanks to new technologies that make it much easier to study them. What biologists have been uncovering is both surprising and disturbing. "It is increasingly clear that these viruses can kill," says Sebastian Johnston of Imperial College London. The common cold is just that: common. We breathe in 15,000 litres of germ-laden air every day, says Ron Eccles, head of the Common Cold Centre at Cardiff University in the UK. "The respiratory system is constantly under attack." While the respiratory system does have formidable immune defences, a slew of viruses are staying one step ahead in the arms race. They cause acute upper respiratory tract infections, aka the common cold. Adults typically have two to four colds a year, while young children have six to ten. Astonishingly, we have no idea how many viruses lie behind such infections. More than 200 members of nearly a dozen families of viruses are known to cause colds (see "The culprits"), but it is becoming clear that many more are out there. The reason for our ignorance is that the traditional method for identifying cold viruses is to grow them in culture. Doctors take a sample of mucus - snot - and add it to a thin layer of human cells in a dish to see what virus replicates. This is how rhinoviruses, thought to cause up to half of all colds, were discovered in the 1960s. However, live viruses often do not survive sampling and culturing, and the method can fail to identify which virus is behind a cold in a third of cases.
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Now, however, researchers don't need to grow viruses to identify them. With the help of PCR, which amplifies the amount of DNA in a sample, they can look directly for viral DNA or RNA sequences. To everyone's surprise, this is turning up cold viruses that are completely new to
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Is%20the%20common%20cold%20becoming%20a%20killer - Is the...

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