Tests Suggest Virus Link
Lab Samples From 2 Outbreak Victims Show Signs of Microbe
By Rob Stein
Washington Post Staff Writer
Wednesday, March 19, 2003; Page A09
Scientists have found evidence of a virus in at least two patients stricken by the mysterious, sometimes deadly respiratory infection that has triggered a global health alert, officials said yesterday.
Laboratories in Germany and Hong Kong testing samples from victims found signs of a microbe known as a paramyxovirus, a family of viruses that can cause a spectrum of diseases in animals and humans, officials said.
Some paramyxoviruses can cause relatively mild respiratory illness. Others cause well-known ailments such as mumps and measles, and still others are responsible for exotic, deadly respiratory infections that emerged in Asia and Australia in the 1990s, officials said.
Although the discovery could be a major break in the hunt for the cause of the global outbreak, officials cautioned that the findings were preliminary and that the virus could have nothing to do with the disease, which is dubbed severe acute respiratory syndrome (SARS).
"It's still preliminary, and it would be wrong to say they found the source of the outbreak," said David L. Heymann, head of communicable diseases for the World Health Organization. "But it's a clue, and encouraging that they're finding something, finally."
Coincidentally, the National Academy of Sciences released a report yesterday urging the world to improve its abilities to detect and combat infectious diseases, whether occurring naturally or through bioterrorism. Among the recommendations was to bar the use of antibiotics that people might need to boost animal growth, which would help prevent pathogens from becoming resistant.
In the current outbreak, researchers in the 11 laboratories working on the disease around the world immediately began testing additional samples to see if they could detect the virus, Heymann said. Results could come as early as today, he said.
There are no effective treatments for diseases caused by paramyxoviruses, Heymann said, although many can be prevented with vaccines.
Paramyxoviruses include the Hendra virus, which emerged in Australia in 1994, and the Nipah virus, which erupted in Malaysia and Singapore in 1999. Scientists determined that the Hendra virus was spread to horses by fruit bats, but not before three people became infected by close contact with sick horses, including two who died.
Nipah is spread to humans from pigs, prompting officials to slaughter thousands of the animals to bring that outbreak under control. But paramyxoviruses also include the respiratory syncytial virus, a common cause of lower respiratory infections, usually mild, in children.
"It's as if you looked at a family of people. One is tall. One is short. One is particularly nasty, while one is sitting calmly in the corner," said Klaus Stohr, who heads the WHO's global influenza program. "That's like this family."
Because paramyxoviruses can cause deadly respiratory infections and have jumped from animals to humans before, they would make logical candidates for the current outbreak, which began in China and has scattered across Asia and into Europe and Canada, experts said.
"This does sound like a plausible possibility," said Stephen S. Morse, an infectious disease expert at Columbia University in New York. "It's great to have a clue."
The viral particles found in the SARS patients were detected with an electron microscope, which enables researchers to see extremely small structures. But "it's as if you were looking at the shadow of someone and don't see the face, but it looks like someone you know," Heymann said. The Hong Kong researchers tested about 30 patients and found evidence of the virus in one, officials said.
"We're all excited because we found something, but we don't want to jump to conclusions. We have to be a bit cautious here," Stohr said. "It's exciting, because it might be a lead. However, we're not there yet."
Chinese researchers had found evidence of a microbe known as chlamydia in victims of what is believed to be a related outbreak in the Guangdong province. But that turned out to be unrelated, experts noted.
In addition to testing more patients, researchers will likely try to grow the virus in the laboratory and identify genetic material from the virus using polymerase chain reaction (PCR), Morse said.
The announcement came as the number of cases of the illness mounted. At least 219 cases have been found in China, Vietnam, Germany, Canada, Singapore, Hong Kong, Taiwan, Thailand, Slovenia and Britain, and at least four people have died. More than 300 other cases and at least five deaths have been reported in the Guangdong province of China. That outbreak, which began in November, was continuing, contrary to earlier reports that it had subsided, said WHO spokesman Dick Thompson.
Health officials in other countries, including the United States, Australia and Israel, are investigating other possible cases, officials said. Two suspected cases in Switzerland were ruled out.
washingtonpost.com |
