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TUESDAY, July 15, 2003 (HealthDayNews) -- Now that the world is catching a breather from SARS, scientists are summing up what they know about the clinical features of this new lung disease.
To wit: Infection with the SARS virus leads to critical illness in as many as one-quarter of patients. These people typically require prolonged treatment with respirators. Nearly half of those that do need mechanical breathing help die of the infection. In addition to serious lung damage, other deadly complications can include multiple organ failure, blood clots and shock resulting from blood infection.
This picture emerges from reviews of nearly 400 SARS cases in Singapore and Toronto, the only North American city with a major outbreak. The two studies appear in the July 16 issue of the Journal of the American Medical Association.
More than 30 days have passed since the last suspected case of SARS in Toronto, and U.S. officials last week lifted a travel alert that had been in effect since late April for that city. The World Health Organization has declared SARS contained, but not before the virus sickened more than 8,400 people in 30 countries and killed more than 800.
Most cases occurred in China, where the disease originated, perhaps by jumping to people who ate infected civets. The infection is believed to be caused by a new form of coronavirus, a pathogen which until now rarely was linked to serious illness in people.
About a third of people infected with the SARS virus became critically ill and the death rate from the disease could approach 10 percent.
"A fairly large proportion of patients do get critically ill and the mortality rate is fairly high in those patients," says Dr. Stephen E. Lapinsky, associate director of the intensive care unit (ICU) at Toronto's Mount Sinai Hospital and a co-author of one of the journal articles.
In Toronto, where 196 people contracted SARS, those who died of the disease tended to be elderly and to have type 2 diabetes -- a finding which continues to puzzle researchers. In Singapore, the death rate from SARS was 13 percent for patients under 60, but soared to 43 percent for those over that age.
The surge in critically ill people during the outbreak taxed Lapinsky's unit and other ICUs in Toronto. Beds were in short supply, while many health-care workers who would have helped treat SARS patients were themselves quarantined, he says.
Since many cases of SARS likely have gone unreported, researchers don't know the true caseload of the disease. SARS in Canada was almost exclusively a hospital-acquired infection, with almost no cases picked up in the community. Ascertaining the true prevalence of the disease is also complicated because some people who contract the SARS virus never develop symptoms.
SARS's behavior and clinical appearance do offer some reason for reassurance, says Dr. Allan Detsky, a physician at Toronto General Hospital who treated patients in the outbreak there and is a co-author of one of the studies.
"If you have a runny nose and productive cough -- one with stuff coming out -- that is not SARS," Detsky says. "The second thing is that in North America, at least, you have to be in pretty close contact to someone to become symptomatically ill. It's not a disease that you get on the subway or by going to a hockey game."
While SARS is quiet now, the disease has made a lasting impact on health-care systems.
In Toronto, for example, the ferocity of the infection and its rapid spread in hospitals forced intensive care units to recast the way health workers deal with patients suspected of having the virus.
No longer do SARS patients in that country receive medication and oxygen through aerosolizing masks, unless they are in pressurized rooms that prevent cough droplets from escaping. Doctors and nurses now enter patient rooms clad from head to toe in protective gear, masks, gowns, goggles and gloves.
"You can't just walk in" to a room with a SARS patient, says Detsky. "Youneed much better protection."
Placing breathing tubes in SARS patients is also trickier than for people with conventional forms of pneumonia. On two occasions, the act of "intubating" SARS patients caused "spills" that led to additional infections. Hospitals now need to have filters and hoods in place to contain the SARS virus before doctors insert the breathing aids.
The Toronto outbreak even affected the way scientists performed research, Detsky adds. After one of the researchers analyzing the behavior of SARS fell ill with the virus, the study team members decided they could no longer meet in person. "We were holed up in our offices with masks on," orchestrating the study over the telephone," he says.
Ultimately, says Detsky, the scientists overcame that obstacle to produce two papers on the outbreak in their city. The feat was remarkable not only for the isolation of the researchers, but also because the work included patients from 10 local hospitals.
Yet while SARS may be a new and deadly respiratory ailment, in many ways its impact on patients is well known to doctors, says Dr. Gordon D. Rubenfeld, of the University of Washington in Seattle. SARS falls into a category of illness called acute respiratory distress syndrome, or ARDS, used to describe the kind of airway trauma caused by not only infections but inhalation of toxic chemicals and other harmful substances. Acute lung damage may cause more deaths each year in this country than emphysema or AIDS.
"When [SARS] patients become ill, there's nothing that unusual about them," says Rubenfeld, author of an editorial accompanying the journal articles. "The one part of SARS that's very different [from other ARDS] is the infection-control issues, particularly to health-care workers. But that has nothing to do with managing SARS and helping the patient."
What's needed, Rubenfeld says, are better treatments for ARDS. In the Asian outbreaks, doctors gave patients anti-viral drugs and steroids, even though there's no evidence these therapies help fight the virus. "We don't have enough information about how to care for [SARS]," he says, but the same holds for other ARDS.