An international team of researchers has developed a drug they say appears to be effective in treating monkeys infected with Severe Acute Respiratory Syndrome, or SARS. The scientists describe the therapy in the current issue of the journal, Nature Medicine. But some scientists are skeptical the drug would work well in humans.

SARS, or Severe Acute Respiratory Syndrome, started in Southern China in late 2002 and spread around the world, infecting around 8,000 people and killing nearly 800, before it was brought under control. Most of the deaths occurred in China, Hong Kong, Viet Nam, and Singapore.

The therapy described in Nature Medicine involves something called small interfering RNAs. RNA is the chemical messenger of DNA, the genetic material found in every cell. In the case of SARS, the virus infects cells, hijacking the DNA to cause the illness.

In the article, U.S., Chinese and German researchers describe how they developed a drug to block the chemical messengers used by the virus. The drug, which uses small interfering RNAs, stopped the disease process in rhesus macaque monkeys exposed to SARS.

After a few days of being treated with the drug, the animals' fevers fell, according to the investigators. They also claim there was minimal damage to the macaques' lungs. In addition to high fever, SARS causes pneumonia-like symptoms.

The researchers also found the drug kept healthy monkeys from becoming sick.

Patrick Lu of Intradigm Corporation of Rockville, Maryland, is one of the study's authors. "Basically, all this strong evidence support[s] the conclusion that treatment is able to relieve animals of the SARS virus-caused symptoms," he said.

Other researchers who have worked with short interfering RNAs, called s-i-RNAs for short, does not think the s-i-RNA therapy will work in humans.

"s-i-RNA has been somewhat disappointing, I think, as a therapeutic regimen in viral infection," said virologist Michael Buchmeier of Scripps Research Institute in La Jolla, California.

Mr. Buchmeier says macaque monkeys, like those used in the study, do not get very sick with SARS, so it is not clear the therapy would work in humans.

In a real life outbreak, Mr. Buchmeier says, the virus would likely change it's shape, or mutate, rendering any s-i-RNA drug ineffective. He says more work needs to be done.

"While it [the research] is very interesting, it is certainly not conclusive," he added. "But quite frankly, it's not going to change the work that we do."

Nonetheless, the researchers who authored the Nature Medicine study hope to begin the first round of human safety trials of their s-i-RNA drug in the near future.