Wednesday, March 19, 2003

Killer pneumonia likely to be new bug

NewScientist.com news service

A new microbe that has jumped from animals to humans is likely to be the cause of the deadly pneumonia that has spread rapidly around the globe. This is the conclusion of international scientists who have tested for virtually every known human pathogen without success.

The highly infectious illness - dubbed Severe Acute Respiratory Syndrome (SARS) - has so far claimed at least nine lives from a total of over 500 cases. The outbreak has prompted serious concern at the World Health Organization and other health authorities.

The recent spread around the world stems from a single case in Hanoi, Vietnam. The Far East has been worst hit, with Vietnam now having 54 cases, Hong Kong having 123 and Singapore having 23, according to reports on Tuesday.

An earlier outbreak in China's Guangdong province, which resulted in over 300 cases and five deaths, is thought to be linked. Other countries affected by the outbreak include Canada, Australia, Thailand, Taiwan, UK, Slovenia, Germany and Israel.

Scientists in 11 international laboratories, coordinated by the WHO, are working flat out to identify the cause of the illness. WHO spokesman Ian Simpson told New Scientist: "The list of things tested for is vast. Everything which has ever been known to cause respiratory infections has been tested for, plus some others not known to cause respiratory infections. It's looking increasingly unlikely that it's caused by something we know about already."

Prime suspect

Influenza had been a prime suspect, and a fearsome prospect given its history of pandemics, but all known strains of influenza and its components have been tested without success. In addition, "pretty much all other viruses known to affect humans and most common bacterial infections" have been tested, Simpson says.

Pneumonia is an inflammation of the lungs caused by a bacterial, viral or fungal infection. Atypical pneumonia, as SARS was initially called, is usually caused by bacteria such as Legionella pneumophila, Chlamydia pneumoniae and Mycoplasma pneumoniae.

Simpson said organisms like Chlamydia and Legionella had not shown up in tests. But he added that the WHO was not completely ruling out anything and scientists were "triple and quadruple testing".

Chlamydia was implicated via lung x-rays in two deaths in the Chinese outbreak. However, Simpson said the Chinese authorities were now questioning this conclusion.

He said: "They now wonder whether that is correct. An awful lot of the population would test positive anyway if you just did a random Chlamydia test." WHO experts are now flying out to China to help the authorities review their evidence.

Bioweapon agent

Among the bacteria being tested, although not commonly associated with respiratory illnesses, is Neisseria meningitidis which causes meningitis. In addition, tests have been carried out for organisms like plague and Brucellosis - pathogens commonly considered as potential bioweapons.

"The reason [for testing biothreat agents] is just because they exist and people are scratching their heads for anything. Nobody can absolutely rule out the possibility of it being a biological agent, but if it is most people here would eat their hats," said Simpson.

He said laboratories were re-testing samples and examining the possibility that the culprit organism could be an entirely new emerging disease like AIDS, Ebola or Nipah virus, probably having crossed over to humans from animals.

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