Researchers in Germany and Hong Kong said Tuesday that they have identified a virus that may play a role in the mysterious pneumonia-like illness that recently emerged from Asia and has infected more than 500 people and killed nine worldwide.
Using an electron microscope to examine sputum and throat swabs from a Singapore physician now hospitalized in Germany, a German team found virus particles that appear to resemble paramyxoviruses, a common strain of viruses that causes many human diseases.
Dr. Wolfgang Preiser of Frankfurt University Hospital cautioned, however, that the researchers have not yet confirmed that the visible particles are, in fact, viruses -- much less that they actually cause the disease, which is now known as severe acute respiratory distress syndrome, or SARS.
"It could possibly, potentially be the agent responsible for SARS, but we don't know at this stage," Preiser said.
Dr. John Tam and his colleagues at the Prince of Wales Hospital and the Chinese University of Hong Kong said later in the day that they had also identified a paramyxovirus using electron microscopy on a sample from a SARS patient in that city. They also determined the genetic sequence of the virus, confirming that it is from the paramyxovirus family. They have not yet revealed whether it is a novel virus or one that is already well known.
The World Health Organization said Tuesday that there have been 219 cases of SARS and four deaths reported worldwide in the last few weeks, in addition to more than 300 cases and five deaths reported earlier in China. Dr. James Hughes of the federal Centers for Disease Control and Prevention said that the CDC had eliminated five suspect cases in the United States, leaving nine that are still considered suspicious. Most experts believe that none of these nine is a genuine case, however.
The paramyxovirus family includes such common viruses as mumps, measles and respiratory syncytial virus, as well as other viruses that cause respiratory infections. Because they are so widespread, experts said, it might not be unusual to find them as innocuous passengers in the patients' fluids.
In recent years, researchers have identified several previously unknown paramyxoviruses, including two -- Hendra virus and Nipah virus -- that have been responsible for outbreaks of severe disease and deaths in humans.
The Hendra virus was transmitted to humans by horses, while Nipah was transmitted by pigs.
The paramyxoviruses do not respond to any antiviral agents or antibiotics.