Will SARS come back? Experts agree only on this: It won't be the last worldwide killer epidemic.
A year ago, severe acute respiratory syndrome -- SARS -- was unknown. Like a winged dragon, it suddenly emerged from China, taking only a month to spread death from Asia to North America.
And like a sleeping dragon, it's now nowhere to be found. Unless, of course, it wakes again. Will it? If anyone would know, that person would be Jeffrey Koplan, MD, MPH, former CDC director and longtime CDC disease detective, now vice president for academic health affairs at Emory University in Atlanta.
"Unknown," Koplan tells WebMD. "SARS can not come back; it can come back. Anyone who gives a firm statement of, 'This is what will happen with SARS,' I don't know where they are getting their information."
What is known, Koplan says, is that there's more than one sleeping dragon.
"The best-case scenario is we learn from SARS and prepare for what is going to be an inevitable return of this virus or something like it -- or something worse," Koplan says. "The worst case is we say, 'This isn't coming back,' or say, 'Other things are more urgent.' In that case, we are no better off than before. Right now, we are closer to nowhere."
This is the story of SARS -- so far. It's about what happened. It's about what we know and what we don't know. And it's about what, at our peril, we refuse to learn.
Unusual Pneumonia
The ancient city of Foshan sits in the Pearl River delta of southeast China. Foshan is home to some 320,000 people. It's an industrial city, but its exquisite silks and porcelains -- and its famous Cantonese cooking -- make it a popular tourist destination.
In November 2002, people in Foshan began coming down with an unusually severe pneumonia. By January 2003, this pneumonia had spread to the nearby -- and larger -- city of Guangzhou. But it wasn't until mid-February that the World Health Organization got its first official report of 305 cases and five deaths from an unidentified respiratory disease.
By then, SARS had taken flight -- literally. The worldwide epidemic began when a doctor who had been treating SARS patients flew to Hong Kong and checked in at the Metropol Hotel. In just a few days, he infected at least 17 other hotel guests. They carried the disease to Toronto, Vietnam, and Singapore.
Donald E. Low, MD, chief microbiologist at Mt. Sinai Hospital in Toronto, was in Hong Kong at that time. His hotel was down the street from the Metropol.
"I flew back the next day, and the SARS patient [who carried the disease to Canada] was on the same plane the next day," Low tells WebMD. "In that one day, SARS moved across the globe from Hong Kong to Toronto."
On March 12, 2003, the WHO issued a global SARS alert. Eventually, SARS spread to 26 countries on five continents. More than 8,000 people fell ill. There were 774 confirmed SARS deaths -- about a 10% case-fatality rate.
Stopping SARS
What ended the SARS epidemic? Klaus Stöhr, PhD, director of the WHO's global SARS laboratory network, credits early identification and isolation of SARS patients. It took heroic efforts from health officials in Hong Kong and elsewhere, who refused to allow anyone with a fever to board any form of transportation. Moreover, air travel to cities with ongoing SARS outbreaks virtually ceased.
"Most countries did temperature screening," Stöhr tells WebMD. "In Hong Kong, every day there were 750,000 people screened at airports, seaports, and land ports. Every day, several hundred people were found to be feverish, and quite a number turned out to be suspected cases of SARS. That is one measure that worked to limit the number of cases. Also helpful was the recommendation to the public to suspend air travel to countries where SARS cases were occurring in the community. These are two measures that we considered successful."
As it turned out, SARS wasn't as easily spread as it first seemed. Most cases could be traced to "superspreaders" -- a few people who became especially ill with especially large doses of especially infectious virus.
"People who were relatively close to the original source of infection obtained a larger dose of SARS virus, were more severely ill, and secreted a large amount of virus," Stöhr says. "With each link in the chain of transmission, the virus excretion rate changed. Those first in the chain were most severely infected. But the super spreading was mostly seen in the initial phase of the outbreak when people did not understand the measures that needed to be taken."
Where Did SARS Come From -- and Where Is It Now?
Foshan, China, is in Guangdong province. As elsewhere in southern China, Guangdong markets feature exotic "game food." These live, exotic animals of nearly every imaginable kind are caged very close to one another. They're butchered and eaten as culinary delicacies.
Some of the earliest SARS cases seem to have been in people whose jobs involved dealing with these animals. Blood from people who handle these animals are more likely to have antibodies against the SARS virus than other people working in the same markets. And health authorities have isolated SARS virus from at least two kinds of these animals -- the Himalayan palm civet and the raccoon dog.
This doesn't necessarily mean the animals are the source of SARS. It's possible that the animals caught the virus from humans, and not the other way around. Pets owned by SARS patients in Hong Kong -- cats and dogs -- have been infected with the virus.
Stöhr says it's clear that no humans now have SARS disease. This means there are only five ways the disease could make a comeback:
The SARS virus is hiding in humans. These people would be infected but without symptoms. Stöhr finds this unlikely. Intense, ongoing screening of blood donors and health-care workers in Hong Kong finds no trace of active SARS infection. This fits with the idea that SARS can only be spread by people who are severely ill. "Asymptomatic carriage, if it happens, plays a small role," Stöhr says.
- Silent transmission. If some people got infected but never had an immune response to the SARS virus, they couldn't be detected by SARS screening tests. "This has not been seen at all," Stöhr says.
- The virus might get away from a laboratory where it's being studied. Labs studying the virus might store it unsafely. This happened twice. In the first incident, a lab worker in Singapore became infected. He did not spread the SARS virus, even though he came into close contact with 25 other people. More recently, a worker in a Taiwan military lab was accidentally infected in December 2003. This case is more troubling, as the worker traveled to Singapore after becoming infected. A WHO investigation -- including tracing of all contacts -- is under way.
- A more sinister possibility is the intentional release of the virus. "We do have to be concerned about this virus as it sits in refrigerators around the world," Low says. "I am worried about SARS as a bioterror weapon. It's already been shown to be very effective in bringing health care to its knees."
- If SARS came from animals the first time, it could happen again. "If the original animal reservoir is not detected, one cannot rule out re-emergence, especially as in China there has been no attempt to segregate exotic animals in the marketplace," Stöhr says. "These animals have been allowed back into the markets and are still a threat." But Low sees this as a sign that the original emergence of SARS from animals was a one-time event. "There is no evidence it ever happened before and -- even though the same circumstances remain in place -- it hasn't happened since," he says.
An Incomplete Shield
Just in case, the WHO is supporting research on a SARS vaccine. Stöhr says the goal is to have a vaccine ready for testing in three years. But Koplan points out that even if such a vaccine works, the clinical testing process itself takes years.
And while doctors got a lot better at treating SARS, there's still no specific treatment for the illness -- and no drug that's proven to kill the SARS bug.
Low, for one, isn't worried that SARS will make a comeback.
"We have put this genie back in the bottle," he says.
But since SARS, public health officials everywhere are sleeping with one eye open.
"I think what we've experienced has definitely been a wake-up call with regards to the importance of being prepared for the introduction of new diseases: SARS and what the future will bring," Low says. "That was an incredible learning experience with a steep learning curve."
Canada, he says, has learned its lesson the hard way.
"One of the things SARS has done for us in Ontario and Toronto and spilled over into all of Canada is a recognition of the situation we have put public health in," Low says. "We have decimated public health and not let it grow at the rate science is growing. We live in such a global village. We have to be prepared today. Public health is absolutely essential for infection control. I think we will benefit greatly from this. Hopefully the U.S. will be able to take our example and use that as an argument as to why you have to support public health in the future."
Former CDC director Koplan says he hopes so, too. But he hasn't seen it yet.
"I don't see progress at this point," he says. "With 20% of the population uninsured or underinsured and lacking access to health care, the best bet is they will have to go to work and spread whatever disease they have without being diagnosed. Until we have adequate support for hospital care in public hospitals, they will be overcrowded and overburdened."
In particular, Koplan says, public hospitals lack enough equipment, staff, and surge capacity to deal with even a moderate public-health emergency. The line separating us from disaster, he says, is thin indeed.
"Our public health system is what stands between us and much greater illness and death rates," Koplan says. "We saw it with SARS. We see it this year with flu. And we will see it again. Just as after a crime wave people are quick to support the police, and after a bad performance by kids on standardized tests we want to support schools, after SARS we see that we really need to support our public health departments. They are the ones that give us a much better shot at surviving the next epidemic."