network-like background pattern

Anatomy of an Epidemic

Emerging from a remote corner of China, SARS wreaked havoc in 28 countries—killing hundreds, infecting thousands, quarantining millions, and costing billions. What does SARS mean for the future of public health?

By Jim Duffy

If there was a single moment when SARS turned the corner from frightening mystery to known malady, it came during the last days of Carlo Urbani’s life. SARS didn’t even have a name on February 28, when the Italian physician with the World Health Organization (WHO) saw a patient named Johnny Chen at a hospital in Hanoi.

Speculation at that point about mysterious cases popping up in Asian cities centered on a rumored outbreak of avian flu in China. After examining Chen and learning how he’d infected at least 22 hospital workers, Urbani had his doubts about the flu theory and shared them with WHO colleagues. He convinced Vietnamese officials that they likely had a public health emergency on their hands.

So much has been learned about SARS in the last few months that it’s difficult to appreciate Urbani’s insight. In fact, SARS took a simple, straightforward route to Hanoi. Johnny Chen caught it from Liu Jianlun at a Hong Kong hotel. Liu was a physician at a Chinese hospital that had seen patients with a mysterious respiratory ailment that first appeared among chefs and butchers working with exotic meats in the Guangdong province of southern China.

But those revelations came later. “One important thing we’ve learned here is what an incredible difference key individuals can make in these situations,” says Neal Halsey, MD, professor of International Health. “Everything Urbani did—the way he used his clinical expertise, the way he sounded the alarm, his willingness to ask for help—proved so, so important.”

Urbani himself began showing symptoms while on a flight to Thailand. Scott Dowell, MD, MPH ’90, was with the emergency-response team that rushed to the airport and then sped Urbani to a nearby hospital. Director of an emerging infectious disease program jointly operated by the U.S. Centers for Disease Control and Prevention (CDC) and the Thai Ministry of Public Health, Dowell knew next to nothing about the disease that would soon be dubbed SARS, for severe acute respiratory syndrome.

“We’d had a briefing, but that was about it,” he recalls. “Our indoctrination into this disease came in taking care of Carlo in a makeshift isolation room. He went from a really mild illness to a little respiratory distress to severe distress. Despite everything we tried, it was just an inexorable progression toward death.”

Urbani died on March 29, shortly after the WHO issued its now-famous global travel alert. That alert commenced a whirlwind for the world of public health—the first new global epidemic of the 21st century was here.

At the School, an overflow crowd gathered May 14 to hear a panel of faculty experts discuss the new infectious disease that was dominating global headlines. Dean Alfred Sommer, MD, MHS ’73, drew a round of bittersweet chuckles with his introduction to the session.

“This is pure public health,” he said. “For once we don’t have to explain to people what public health is and why we’ve devoted our whole lives to it.”

SARS infected nearly 8,100 people and killed 774 before its advance slowed in June, but the public health whirlwind it caused still hasn’t let up. Too much remains unknown, uncertain—not the least of which is whether and how seriously SARS will return this winter.

This summer faculty members and alumni reflected on what public health has learned thus far about SARS and how the epidemic might shape the future of the field.

Lesson 1: It really is a small world after all

“One thing is clear—the 747 is a great incubator.” That isn’t a revelation to David Celentano, or to anyone else who logs 100,000 miles a year on airplanes. As the Hopkins epidemiologist tracked early SARS numbers on his office computer in April, he found himself remembering all the colds he’d caught over the years from fellow air travelers. Then he canceled a planned trip to Asia.

Air travel has long been regarded as a potential public health risk. With SARS, that risk became deadly reality—a new infection made its way from a remote corner of China to the Hong Kong airport. From there, it traveled throughout the Asian continent and halfway around the world, all before it even had a name.

“Fifty years ago, an outbreak like this might well have burned itself out locally,” notes Kenrad Nelson, MD, professor of Epidemiology and a former Epidemic Intelligence Service officer. “Disease is global today. So public health has to be global.”

This new reality means that tomorrow's practitioners need to be prepared for all sorts of maddening complications in the fight against infectious disease.

Witness the initial dissembling about SARS numbers by some Chinese authorities. Witness the bureaucratic brouhaha over how—or even whether—the international community could assist Taiwan, a country most of the world doesn't formally recognize. Air travel might make the world a smaller place, but it doesn’t make it any less messy.

“Local, national, WHO: All three need to be working, and they need to be working in unison and without defensiveness,” says Ron Brookmeyer, PhD, chair of the School’s MPH program. “A lot needs to be done to improve the chances that that’s going to happen when it needs to happen.”

Getting there will require years of grunt work: building relationships, opening communication lines, and expanding cooperative capabilities.

That’s the kind of work alumnus Scott Dowell, MD, MPH '90, was doing in Thailand when SARS erupted. The first of its kind in the world, his program lends CDC expertise to nations establishing programs to better detect and control outbreaks of infectious disease. Its mission encompasses training programs, surveillance strategies, and capacity building—the kind of work that more Asian countries are doing in the wake of SARS.

“Public health has suddenly been elevated to a much more important position in many of these places,” Dowell says. “I hope that gives us a push toward strengthening international collaborations so we can put quality public health teams into places where these outbreaks can happen.”

For some School faculty, the urgency of the task raises questions even about domestic spending here in the United States, where many experts have long decried the “dismantling” of the public health infrastructure. The field received 10 percent of health care spending in the 1940s; that's down to 1 percent today, even after a recent boost spurred by fears of bioterrorism.

“But compared to other countries, we’re still in pretty good shape,” says Kenrad Nelson. “What SARS says to me is that we have to be concerned about places all over the world that don’t have good public health systems.”

“We here in the United States need to think seriously about investing in these other countries,” agrees Robert Bollinger, MD, MPH ’88, associate professor of International Health. “Their ability to deal with problems is going to be critical for us as well as for them in the future.”

The international community, on the other hand, needs to beef up WHO’s capabilities. Among School faculty, there is broad agreement that WHO performed commendably in the face of SARS. Its forceful early travel advisory and aggressive surveillance strategies helped stem the spread of an infectious agent that might otherwise have killed many thousands instead of less than 800.

But WHO’s success should not imply that it has all the resources and expertise it needs, warns Neal Halsey. “What’s happened with SARS is such a powerful argument for strengthening the WHO,” he says. “Look at what they accomplished, and then look at their extremely limited resources. It was just nine people doing almost all of what they did out there.”

Lesson 2: We still have gaping holes to fill

In 1996 epidemiologist Don Burke’s research on emerging infectious diseases took him to Cameroon. When a vehicle he was in on that trip struck and killed a wild animal, Burke’s traveling companions threw the carcass in back so they could cook it up for dinner later.

When scientists identified a possible animal reservoir for the coronavirus behind SARS—a cat-sized creature called a civet—Burke searched for his old photos from Cameroon.

“The one and only road-kill meal of my career—and it was a civet,” he says. “It’s pretty good, actually—a little musky, but good.”

Burke’s civet dinner isn’t just an entertaining anecdote. The director of the Department of International Health’s Disease Prevention and Control Program uses it as a starting point in discussing the zoonotic diseases that move from animal reservoirs into human populations. SARS, of course, is just one example of the breed; others include AIDS, Ebola, mad cow disease, and numerous strains of influenza.

In some ways, SARS revealed the revolutionary progress of modern laboratory science. In a matter of a few weeks, researchers identified the mysterious new agent as a coronavirus, pinpointed its likely reservoir in the animal population, and decoded its genomic structure. Vaccine tests were under way in April—for an agent that no one knew existed in January.

And yet SARS simultaneously revealed gaping holes in our scientific knowledge. Virtually no one anticipated that a coronavirus, which previously had caused only minor human maladies, could wreak such havoc. One exception is Burke, who predicted such an outbreak in a 1997 lecture (see sidebar). Today, Burke is a strong advocate for expanding public health research on infectious diseases into animal populations. His own research focuses on the diseases of non-human primates in Africa.

“We know precious little about the reservoir of viruses that are in nature right now that could infect humans,” says Burke, MD. “We ought to do better at looking where the dangers could be. I want to go one step beyond surveillance. I think public health should be trying to understand the systems in which these things arise.”

To many laypersons, the onset of a disease like SARS sounds like a simple matter—somebody caught a bug from an animal and passed it on. But in nature, such transmissions are anything but simple. After all, humans have been butchering and consuming civets for centuries, but no one contracted SARS before, at least as far as we know at the moment.

“This cross-species boundary has been there forever,” Burke says. “There’s nothing magic about this year.” One possible explanation, he explains, is that the virus arose because of a complex, one-of-a-kind chain of recombination or mutation events. “That’s the reason influenza epidemics emerge,” he says. “Flu goes hot when the virus reservoir in the animal population mixes with the viruses that are in humans. The new viruses that emerge from those combinations have mostly human virus and a little bit of animal virus.”

No one knows whether coronaviruses work the same way, but if they do, then SARS might be eradicable in the short term. Burke has been a leading voice in urging the international public health community to heighten its vigilance as SARS wanes, in an effort to catch and break the chain of transmission for every last case in the world.

If SARS, like most respiratory diseases, is a cold weather infection, then the warmer months offer a chance to beat it for good. Burke concedes that this may be a long-shot strategy, but the potential payoff is enormous. “If we can eradicate the agent that’s being transmitted now, that may be it,” Burke says. “If this was a chance recombination event, that means that just because there’s an animal reservoir doesn’t mean SARS is coming back any time soon.”

Lesson 3: Long live Epidemiology 101

Despite the speed with which SARS was identified and decoded, scientific technology can’t take credit for curbing the epidemic. On the streets of cities like Hong Kong and Toronto, that success was the resultof the old-school techniques that Epidemiology 101 students have been learning for decades: surveillance (see sidebar), hygiene, isolation, quarantine.

“When it gets right down to it, we still have to count on that stuff,” says Trish Perl, MD, MSc, the chief epidemiologist at Johns Hopkins Hospital, with a joint appointment in Epidemiology at the School. She traveled to Toronto during the height of that city’s SARS ordeal to relieve exhausted colleagues. “That stuff has been shown to work time and time again. But for some reason getting people to believe that it’s as simple as that is really a challenge.”

One survey cited by Perl indicated that Toronto health care workers who contracted SARS were less likely than their colleagues to abide religiously by hygiene rules.

“Wash your hands—that’s probably the greatest maxim in all of public health,” says David Celentano, director of Infectious Disease Epidemiology. “But it’s a message that seems to be lost on every generation.”

In the age of genomics, who wants to talk about hygiene habits? Or strategies so old they date to biblical times? Celentano, ScD ’77, MHS ’75, recently traveled to Dubrovnik, Croatia, where he marveled at a stark, stone isolation facility built 1,400 years ago outside the city’s walls.

“People scream and yell nowadays about how harsh [quarantine] seems,” Celentano says, “but it works. That’s why we’ve been doing it for centuries.” To Celentano, SARS and bioterrorism should serve as warnings that countries around the world need to sort through all the modern-day legal and liability issues surrounding isolation and quarantine.

In a way, then, SARS brings public health back to the future. “The technology is great, but that shoe-leather epidemiology is still essential,” says Ron Brookmeyer. “You need to recognize a threat, identify it, track it. You still need all that Epidemiology 101 stuff to break the chain of transmission.”

Lesson  4: Don’t underestimate the dangers ahead

With rapid transmission rates and a fatality rate of somewhere between 5 and 10 percent, SARS’ numbers told a frightening story.

But they didn’t tell anywhere near the whole story that Scott Dowell witnessed on the front lines. In a few short months, SARS disrupted the lives and livelihoods of millions of people across a broad swath of the Asian continent. In mid-May, nearly a million people were under quarantine in Taiwan alone. When Dowell visited Beijing, he found a city of deserted streets, empty restaurants, and nearly empty hotels.

“It’s probably hard to appreciate from the U.S. just how substantially SARS changed daily life,” Dowell says. “You go to an airport, and not only is it just about empty, but the people doing the pre-boarding screening are essentially in space suits.” 

Trish Perl, too, saw SARS up close, when she helped overtaxed staffers at Toronto’s Scarborough General Hospital. “It was eerie—like you were on Mars or on a new planet,” she told the New York Times. “You sit in meetings, everyone around the table is wearing an N95 mask.”

As a hospital epidemiologist, Perl has special concern for the clinicians, nurses, and technicians who must work in close quarters with infectious diseases while trying to save patients’ lives. “One of the most important messages we need to get out there is that it’s very clear that when we put these people in a health care setting, we are putting them in a place where the environmental conditions are right to ensure transmission,” she says.

Nearly half of the early SARS cases in Toronto were health care workers. Staffers were quarantined in such large numbers that hospitals endured severe shortages of caregivers at the worst possible time. Those who remained on the front lines found themselves ostracized by a public who now saw them as a source of danger. 

Perl worries that an American city might have it worse than Toronto. Canadian hospitals, she says, have a stronger system of psychological counseling to help health care workers grapple with the stress, fear, and guilt sure to arise in such circumstances. Perl fears that Americans would be more likely to balk at isolation and quarantine rules.

Like many of her colleagues, Perl strongly believes that it’s high time the United States reinvests in its public health infrastructure. “It may not be sexy,” she says. “We’re sometimes viewed as the Pus Patrol. But I wish we in health care would take our lessons from the business world, from manufacturing operations—they would never, never, never let go of quality control.”

What happens next with SARS is, at this point, anybody’s guess. There’s a chance, as Don Burke notes, that it will disappear forever. And there’s also a chance that it will reappear with a vengeance.  In the SARS seminar at the School in May, both Burke and Perl showed graphs detailing the events of 1918, when a small wave of deadly flu cases appeared in the spring and then subsided in the warmer months. That turned out to be a “herald wave” for the flu pandemic that killed 20 million in the following fall and winter of 1918.

The most likely scenario, however, lies between those two extremes. “Fortunately, this coronavirus doesn’t seem to be as infectious as the flu,” says Kenrad Nelson, “but it looks to me like it’s very likely to persist, at least at a low level and perhaps becoming endemic in a few places, like China. A year from now, we’ll still be talking about SARS.”

Lesson  5: Public health must learn to lead with speed

Fear moves faster than science. In a world of instant communication, that can be a problem for public health. “This whole thing unfolded so fast over here,” Scott Dowell says from Thailand. “It really outstripped the response from public health officials.”

In Asian cities, people began wearing masks in huge numbers every time they went out in public. No harm was done, but public health officials generally regarded that move as unnecessary. Airlines and airports had to decide what their crews would wear before the WHO could weigh in with recommendations. That’s when airport workers donned those space suits, another excessive measure of protection that might have helped fuel the public fear that—to cite just one example—led pilots to refuse to transport SARS tis-sue samples to laboratories.

“In that respect, our usual public health mechanisms didn’t work so well,” Dowell says. “We were doing what we needed to do, investigations and evaluations and trying to make recommendations based on data. It’s not that there’s blame to be assigned here; it’s just that events unfolded so fast that things moved outside the realm of public health.” That creates a conundrum for public health officials. It’s apparent that they need to learn how to move with lightning speed to communicate with the public. But this means that on occasion they’re going to have to move authoritatively even before they have reliable information.

“What does the public do if they hear there are six SARS cases in their community?” asks Robert Bollinger. “Should they go to work? Should their kids go to school? One of the biggest problems is how to establish the communication lines to allow for an exchange of accurate information between the public health system, the CDC and WHO, the local public health officials, and the public.”

From his up-close vantage point, Dowell thinks the primacy of risk communication is an especially important lesson from the SARS epidemic. 

“If something like this happens in the future, public health leaders better be ready to move incredibly fast, and they better be ready to communicate with the public incredibly well,” Dowell says. “If you don’t do that, you’re going to be following, not leading. The public health system has to respond much more quickly than [we] ever have before. Or we’re going to get pushed aside.”