President's Page June 2003

Robert W. Haley, MD

The ABCs of SARS
The latest emerging threat to world health

On November 16 a Chinese businessman in the small industrial city of Foshan near Guangzhou, the capital city of southern China’s Guangdong province, developed a nearly fatal respiratory illness, which spread to four hospital personnel who cared for him. This was the first known case of what the World Health Organization named Severe Acute Respiratory Syndrome, or SARS. Within weeks, hundreds of similar cases appeared in nearby cities, primarily in family members and hospital personnel who cared for the initial victims. A disproportionate number of the early cases were in chefs and foodhandlers. Throughout recorded history the most virulent new germs, such as smallpox and plague, have emanated from southern China, where it is thought the close living and dining arrangements of humans and diverse animal species encourage adaptation of mutant strains to humans.

Alert local public health officials throughout Guangdong province quickly recognized a serious problem and reported it up the line, but provincial and national officials suppressed the reports and failed to take actions that might have stopped the epidemic at its inception. In February, 13 foreign visitors contracted SARS while guests at Hong Kong’s Metropole Hotel and returned home to spread the virus to other regions, including Vietnam, Singapore, Europe, Canada, and the United States. Vigorous efforts to isolate SARS patients and quarantine their close contacts contained the outbreaks outside China, except in Toronto, where widespread transmission occurred before the problem was recognized. A rare WHO travel advisory on March 10 and the natural fear of epidemics have curtailed travel and retail activity, and seriously injured the economies of the countries where SARS has persisted. The disease now is spreading widely in the interior of China, where overcrowding, poor sanitation, primitive medical facilities, and limited public health organization make it difficult to control.

SARS is a viral infection of the lungs that kills 5 percent to 10 percent of its victims, young or old, by attacking the alveoli and impairing oxygenation. The initial symptoms are indistinguishable from a common cold or influenza, and include fever, muscle aches, sore throat, and nasal discharge, progressing to a dry cough and dyspnea. Some have diarrhea. Severe cases develop unilateral or bilateral patchy infiltrates, such as atypical pneumonia. Corticosteroids and ribavirin appear to ameliorate the symptoms in some people, but may prolong viral shedding.

An unprecedented worldwide collaboration of laboratories, organized by WHO and the Centers for Disease Control and Prevention, rapidly identified a newly emerged member of the coronavirus family as the causative agent and, within three weeks, sequenced its genome. Coronaviruses, named for their crown-like appearance under electron-microscopy, cause a minority of common colds in humans and more serious diseases in many animal species. The SARS strain has partial DNA homology with human, chicken, and horse strains, but is novel. With this knowledge, scientists have developed a research serologic test and are working on a rapid, clinically applicable test. The fact that infected people make antibody to the virus suggests that a vaccine might be possible; however, like most coronaviruses, the SARS virus appears to be mutating rapidly, which could defeat a vaccine.

With no rapid test, curative treatment, or vaccine, the only effective way of dealing with the new threat is to prevent it. Fortunately, transmission of SARS is indolent. The fact that 80 percent to 90 percent of cases affect family members or healthcare personnel who care for cases indicates that the mode of transmission is either large droplets spewed a few feet by coughing and sneezing or contamined hands and environmental surfaces; true airborne spread, such as with tuberculosis, is unlikely. SARS virus also is excreted in urine and feces, and may spread through sewage leaks. Several large clusters of secondary cases traced to a single index case indicate that rare “super-spreaders” are especially infectious.

Transmission of SARS usually can be prevented by rapid identification and isolation of new cases; scrupulous use of masks, gowns, eye shields, and handwashing by care-givers; environmental disinfection with bleach, alcohol, phenol, or formaldehyde; and vigorous health department tracing and quarantine of close contacts of cases. SARS patients should be instructed to cover their coughs and sneezes, avoid touching their faces, and wash their hands thoroughly and often, particularly after going to the bathroom, to avoid infecting their families and care-givers. SARS might just re-establish these habits among the social graces.

The future of SARS is uncertain. Although the SARS virus survives for days on environmental surfaces at cold temperatures, it dies quickly at warmer temperatures. Thus, if hand/surface transmission predominates, SARS will be seasonal, disappearing in the summer, possibly allowing greater opportunities for eradication. If large droplet transmission predominates, it may continue spreading year-round and become endemic in developing countries. Barring a wholesale mutation to avirulence, for the foreseeable future we must expect occasional introductions in the United States, which will threaten healthcare workers and challenge local public health departments. We must learn to deal with it.

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