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Links sars common cold { April 17 2003 } Original Source Link: (May no longer be active)
http://www.washingtonpost.com/wp-dyn/articles/A39713-2003Apr16.htmlhttp://www.washingtonpost.com/wp-dyn/articles/A39713-2003Apr16.html
Scientists Link SARS Virus to Common Cold
By Rob Stein
Washington Post Staff Writer
Thursday, April 17, 2003; 12:00 AM
The alarming new lung infection that has triggered an international health emergency is unquestionably caused by a previously unknown virus related to germs that cause the common cold, the World Health Organization announced today.
Dutch scientists have produced the final pieces of evidence necessary to conclusively link the microbe, known as a coronavirus, to the new disease, severe acute respiratory syndrome (SARS), scientists at the Geneva-based United Nations body said.
While researchers for several weeks have been focusing on the virus as the probable cause of SARS, the definitive connection is nonetheless a crucial milestone in the global health crisis. It will allow scientists around the world racing to fight the epidemic to focus exclusively on the virus, speeding development of better tests for it, aiding efforts to find a way to treat it and helping scientists eventually develop a vaccine to prevent its spread.
"We now know with certainty what causes SARS," said David L. Heymann, executive director of the WHO's communicable disease program. "Now we can move away from methods like isolation and quarantines and move aggressively toward modern intervention strategies including specific treatments and eventually vaccination. With the establishment of a causative agent, we are a crucial step closer."
Heymann also said that scientists had detected evidence of the virus in feces and urine, which would explain why many victims experience diarrhea and other gastrointestinal symptoms. The discovery could mean that the virus can be transmitted through waste, which would explain how the disease spread rapidly through a Hong Kong apartment tower, which has puzzled and alarmed researchers, he said.
"It may be the way in which they are getting infected," said Heymann at a briefing about a one-day meeting of scientists from 13 laboratories in 10 countries that the WHO is coordinating to fight the disease. He stressed, however, that the primary route of transmission is droplets that infected people spray out when they sneeze or cough.
Efforts to contain the disease have focused primarily on identifying and isolating sick people early before they spread the virus. That appears to have been effective in some places, such as Hanoi, Singapore and Toronto. But the disease is still spreading in Hong Kong and mainland China, and sporadic new possible cases continue to be reported throughout the world.
While several tests have been developed for the virus, none are precise enough to answer key questions, such as whether people can spread the virus before and after their symptoms begin and end.
Although much more research is needed to determine where the virus originated, the microbe's genes don't appear similar to any other known coronaviruses, suggesting it has been hiding in nature in southern China, perhaps in an animal, said Masato Tashira of the National Institute of Infectious Diseases in Tokyo. The only two previously known human coronaviruses cause about one-third of all colds, but other coronaviruses infect many different animals, sometimes cause severe respiratory or gastrointestinal diseases.
The announcement firmly associating the coronavirus to SARS came after researchers in the Netherlands discovered two final pieces of evidence: Monkeys infected with the virus developed a disease identical to that seen in humans, and scientists were able to then find virus in the animals.
"We can with all confidence say the causative agent of SARS is the coronavirus," Albert Osterhaus of the Erasmus Medical Center in Roterdam, who led the research, said at the briefing.
Researchers at the University of Hong Kong were the first to isolate the virus from victims in Asia. Scientists at the U.S. Centers for Disease Control and Prevention in Atlanta almost immediately confirmed that the microbe was a coronavirus. Other laboratories in the scientific network assembled by WHO soon found evidence of the coronavirus in additional patients.
But some scientists also found signs of another virus, known as a paramyxovirus, and Chinese scientists said they had evidence that another organism known as chlamydia might be involved.
The WHO network started building the case for the coronavirus. For a virus to be conclusively linked to a disease it must satisfy four criteria, known as Koch's postulates: the microbe must be found in all patients with the disease; it must be isolated from a patient and grown in the laboratory; it must reproduce the disease in an animal, and must be then found in that animal. The Dutch research satisfied the final two criteria, showing that monkeys infected with the coronavirus developed the disease, those infected with the paramyxovirus did not and those infected with both did not get sicker than if they were infected with the coronavirus alone.
"The coronavirus alone is capable of causing the typical symptoms," Osterhaus said. "The coronavirus is the primary cause of the disease."
The WHO is calling the pathogen the SARS virus and dedicated the discovery to Carlo Urbani, the WHO scientist who first alerted the world to the nascent epidemic before dying from the disease himself.
Earlier this week scientists at the CDC and in Canada released the virus's complete genetic code.
The speed with which the microbe was identified, its genome deciphered and its link to the disease proven, was unprecedented, illustrating the urgency to fight the epidemic. Scientists put aside typical personal concern about fame or profit from their work.
"All of this has been set aside. All of this has been overcome by the understanding that we are being faced with a public health emergency," said Klaus Stohr, who is coordinating the WHO network.
The SARS epidemic apparently began in the southern Chinese province of Guangdong in November, spread to Hong Kong by an infected doctor and then elsewhere by travelers visiting Hong Kong.
At least 3,293 suspected cases have now been reported in 23 countries, and 159 victims have died. Hong Kong and southern China have been hit hardest. Outside Asia, Toronto is the worst SARS hot spot.
U.S. health officials are investigating at least 193 cases in 32 states, including five in Virginia, but are expected to sharply reduce that number this week when they narrow their definition of the disease to bring it in line with the WHO. Most of the cases have been among people who recently returned from Asia, but a handful have been health care workers and family members infected by the travelers.
© 2003 The Washington Post Company
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