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Mystery Pneumonia-Like Virus Identified - 2003-03-20

The virus found in patients with a mysterious pneumonia-like illness in Asia is from a family of organisms known as paramyxoviruses. Public health officials are examining it closely under the microscope to see what they can learn about it and whether it causes the new disease.

Laboratories around the world are trying to determine whether the paramyxovirus swabbed from the noses of German and Hong Kong patients with the Asian pneumonia is new or something seen before.

Public health experts do not yet know whether the virus is linked to the so-called severe acute respiratory syndrome, or SARS, because it has been found only in patients' noses. The head of the U.S. government's Centers for Disease Control (CDC), Dr. Julie Gerberding, says disease trackers need better proof of a connection. "It hasn't yet been identified from any tissues or lung material or other specimens that would directly implicate it as a cause of the infection."

Whether or not the virus is linked to SARS, CDC officials suspect it is a new form because laboratories have not been able to identify it.

Most paramyxoviruses are benign and cause illnesses that are generally not lethal -- measles, mumps, and some forms of the common cold, for example.

But a retired virus expert in Washington, Dr. David Kingsbury, says more virulent forms have appeared in recent years. In 1994, the Hendra virus killed two people in Australia who had been in close contact with horses. Dr. Kingsbury points out that the Nipah virus outbreak in Singapore and Malaysia four years ago jumped to people from pigs and was linked to severe encephalitis, an often fatal brain inflammation. "It's a classic scenario that when an adapted agent in one species encounters a new species, there can often be a bad interaction," he says.

No one is sure that is the case with this unknown paramyxovirus, but experts say that because organisms from this group have jumped from animals to people before and can cause deadly lung illness, the viruses are logical candidates for the current SARS outbreak.

If they are the cause, treatments are unknown. There are few drugs for viruses, as Columbia University infectious disease expert Stephen Morse points out. "Many of the bacterial diseases can be treated with antibiotics. With viruses, this is much harder to do," he says. "We have very few antivirals. Most of them are very specific to a virus or a family of viruses." But Dr. Morse adds that much can be done to treat the symptoms of severe respiratory infections like SARS, including ventilators to aid breathing and steroids to reduce inflammation.

Public health officials note that SARS appears to be transmitted by close contact, judging from the cases that have occurred in hospitals, hotels, and families. Dr. Morse believes that will limit its spread. "The information to date seems to suggest that it's transmitted by the respiratory [breathing] route through droplets, spray, something like that," he says. "It requires fairly close contact. It does not seem to be spreading rapidly through casual contact, which is good news."

SARS is tough to diagnose, however. It symptoms are common to many other illnesses fever, coughing, breathing difficulties, and chest discomfort. This makes tracking it hard. As a result, U.S. public health officials are warning anyone returning by sea or air from Hong Kong or other parts of Asia to seek medical help if they suffer such symptoms within one week of departure.