Report from ICAAC:
SARS studies answer, raise questions
By Anita Manning, USA TODAY
CHICAGO ? Six months after the World Health Organization's first global alert of SARS, scientists are unraveling some of its mysteries. But many questions remain, including the big one: Will it come back?
Scientists from around the world presented at least a dozen research papers and lectures on SARS this week at the Interscience Conference on Antimicrobial Agents and Chemotherapy, the American Society for Microbiology's annual meeting on infectious diseases. Among the highlights:
? In children, SARS, or severe acute respiratory syndrome, causes a relatively mild illness compared with adults, researchers at the Hospital for Sick Children in Toronto say. None of the 25 children treated there for SARS needed to be put in intensive-care units or required ventilator support. All made a full recovery. Younger children were less likely to pass the disease to others and fared better than teenagers, whose illness was more like that of adults, researchers said.
? Diagnosis of SARS by polymerase chain reaction, or PCR, which detects viral DNA, is not reliable in children or in early stages of the disease in adults, researchers say. In SARS, unlike other respiratory illnesses, the viral concentration builds up, peaks at about 10 days after the start of the illness and then drops off, says Malik Peiris of the University of Hong Kong. In influenza and other respiratory diseases, the viral load is heaviest at the start of the illness.
? Contagion increases with the severity of disease, so it's most likely to spread around the 10th day of illness, when the virus is at its peak. That's also when the sickest patients are in the hospital and helps explain why 20% of the cases occurred in health care workers, Peiris says. Fewer family members of SARS patients caught the disease at home, yet there are examples of hospital visitors and nurses who were rooms away from a SARS patient and still became infected.
"The majority of patients who get SARS don't transmit it," says Allison McGeer of Mount Sinai Hospital in Toronto. "But sometimes they do, and we don't know why." McGeer, who contracted SARS herself, says the disease is most often spread by droplets expelled by sick patients, but there remain "some questions of airborne transmission."
? Three phases of the disease were seen: In the first week, there is fever (it may drop and resurge in the second week) and other symptoms such as chills, cough and dizziness. About 20% to 40% of patients also had severe diarrhea; in the second week, pneumonia and breathing problems begin; in the third week, the patient either starts to recover or there is lung destruction. SARS was fatal in 6% to 16% of cases, and 20% to 25% of patients required intensive care.
? Tests show that most people infected with SARS get sick, so it's unlikely that SARS is spread widely by people who have no symptoms. The disease is most dangerous in older people. In Canada, in people over 65, the death rate was nearly 50%.
Though SARS affected 8,422 people worldwide, there were only eight confirmed cases in the USA, says Larry Anderson of the Centers for Disease Control and Prevention, but that's no reason for complacency. Other respiratory viruses are seasonal, he says, and there are several ways SARS could come back, including reintroduction from animals, believed to be the original source of the disease, or lab accidents, which may have caused a case recently in Singapore.
It's critical that more be learned about where SARS hides out in nature, says James Hughes, director of the National Center for Infectious Diseases at the CDC, and health officials should be on guard. "This disease could be back with us at any point."
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