DOCTORS WORK TO IDENTIFY PATHOGEN
17 Mar 2003
Source: Wall Street Journal, March 17, 2003
Doctors Work to Identify Pathogen For Deadly Pneumonia Breakout
By ANN CARRNS, MARILYN CHASE and ANTONIO REGALADO, Staff Reporters of THE WALL STREET JOURNAL
The world's leading infectious-disease laboratories swung into action over the weekend as part of a fast-moving effort to identify the cause of a mysterious pneumonia outbreak that is popping up outside of its original hot zone in China.
The coordinated effort to track the disease and determine its nature demonstrates not only the available technology, but also the heightened awareness among global health officials of new scourges, arising in part from fears of bioterrorism. Indeed, while health officials say it is highly unlikely that the disease is linked at all to bioterrorism, the global effort will help hone skills for protecting public health in emergencies.
Tests so far have looked at a variety of tissue samples, including those taken during an autopsy on at least one of the patients who died in Canada, after traveling to Hong Kong. These include samples of blood and other bodily fluids, along with tissue samples from the lungs, liver, spleen, brain and kidney.
Scientists typically screen the blood for the presence of antibodies, the defensive molecules produced by the immune system when it detects foreign invaders. However, because it takes the body several days to mount an antibody response that can be measured, such tests aren't always useful.
Doctors researching the infection also have performed a procedure called alveolar lavage, where liquid is flushed through the trachea and then collected for cell culture tests. The culture tests look for the death of different types of cells that normally would be susceptible to a particular pathogen, or germ.
"You say, 'Uh-oh, this cell is dying,' " said Klaus Stohr, manager of the World Health Organization's Influenza Program, adding that the tests provide a clue to the family of viruses that may be at work. However, such tests take days, or even weeks for conclusive results.
While the cause of the illness still hasn't been pinpointed, one possible suspect is the Nipah virus, a newly identified pig virus responsible for sickening and killing swine farmers in the late 1990s.
Experts say they are leaning toward a virus, Nipah or otherwise, as the cause of the current outbreak because bacteria are larger, and would likely have been spotted already with a high-powered microscope if they were the culprit. For instance, doctors found swarms of anthrax bacteria in the spinal fluid of the first person killed in the anthrax attacks of 2001.
James Hughes, head of the infectious disease center at the federal Centers for Disease Control and Prevention in Atlanta, which is collaborating with the WHO, said his agency is conducting a variety of tests to identify the agent, such as attempting to grow the infectious agents; injecting mice with material from the samples, to try and induce the disease; and various molecular testing techniques.
Testing for viral genes and proteins also comes into play. Some such tests, Dr. Stohr said, already have been done, and one result is that "there are no indications that influenza is involved in the outbreak." Other scientists say influenza shouldn't yet be ruled out.
If no common virus or bacteria is found to be the actual pathogen causing the disease, the detective work will become more difficult. "Then we are dealing with the possibility of a brand new agent," Anthony Fauci, head of the National Institute of Allergy and Infectious Disease in Bethesda, Md., said, adding, "or an agent that has mutated so much we can't identify it."
Scientists would then begin a laborious process of searching for any similarities to known pathogens, Dr. Fauci said. The hunt for the agent's DNA also would widen: Scientists would begin scanning more broadly for genes that bear similarities to known micro-organisms.
The research work is truly global. About eight scientific institutions are assisting Hong Kong University laboratories as part of WHO's international consortium of research laboratories with the facilities to conduct sophisticated tests. Among them: The CDC, the Pasteur Institute in Paris, the Public Health Laboratory Services in London, the Institute for Tropical Medicine in Hamburg and Erasmus University in Rotterdam.
Potential treatments would of course depend on what the cause of the illness is determined to be. If a virus is found to be the culprit, Dr. Hughes acknowledged, there may be no immediate treatment. If it does turn out to be a type of flu, research could begin on a new vaccine, although that is usually a lengthy process.