he onslaught of infectious disease has caught some health care experts by surprise. At mid-century the dream of eradicating the world’s most dreaded afflictions seemed within our grasp: vaccines for polio, smallpox, diphtheria, tetanus, and other illnesses were saving millions of lives each year. Penicillin and other antibiotics were developed to cure life-threatening diseases, such as tuberculosis and syphilis. So hopeful were public health officials that many young physicians viewed infectious disease as a medical specialty with little future. “I don’t think I really learned about anthrax, smallpox, or hemorrhagic fever until recently,” says Alan Hartstein, a veteran professor of infectious disease at the School of Medicine. “When I was a young man we all thought that these diseases were all under control. What a mistake that has proved to be.”

Consider tuberculosis. World health officials once believed that outbreaks of this highly contagious bacterial infection might one day be contained to perhaps a small, manageable handful per year, scattered around the globe. But with drug-resistant strains of the disease cropping up almost as soon as new antibiotics are introduced, that dream is fading. Last year more than two million people worldwide died from tuberculosis. The disease poses a threat not only to the rural and urban poor but also to health care workers in the most advanced clinical settings. Hartstein serves as the chief of infection control at the University of Miami/Jackson Memorial Medical Center, helping to reduce the chances that infected patients will transmit disease to other patients and to hospital workers. Containing tuberculosis, he says, is among the greatest challenges.

Other diseases remain a threat because of bioterrorism. Smallpox was once believed eradicated, forever removed as a threat to human health. But researchers now are investigating new vaccination and treatment options in the event of a wide-scale attack. At the University, which houses a high security germ lab, researchers are studying the bacteria that cause bubonic and pneumonic plague. School of Medicine associate professor Gregory Plano hopes to determine how the disease at the molecular level invades its human host. He says only a handful of new cases appear in the United States each year, transmitted principally by fleas from infected rodents. But researchers hope to develop a vaccine against a separate form of the disease that is transmitted by airborne particles—the most likely form of an outbreak caused by a bioterrorism attack.

Perhaps the most alarming threat is posed by newly emerging diseases and by ones lying dormant in remote areas of the world. After leveling off during the first half of the 20th century, worldwide deaths caused by infectious disease are skyrocketing, mostly due to diseases unknown a few decades ago. In barely a quarter century, AIDS has swept the planet, today infecting an estimated 42 million people. Outbreaks of more exotic diseases such as Ebola, an agonizing hemorrhagic fever with a high mortality rate, are occurring with increasing frequency since first appearing in the early 1980s. “West Nile virus was first recognized in humans in 1937 and has been causing disease in Europe, Africa, and Asia ever since,” says Gio Baracco, assistant professor in the Division of Infectious Diseases at the School of Medicine. “But it had not been seen in the Americas until 1999.” The disease has sickened nearly 5,000 people this year, killing 95.

Experts blame the sudden emergence of infectious diseases on a variety of mostly human influences—deforestation, increased urbanization, climate change, war and famine, to name a few. In short, explains Hartstein, new diseases appear and old ones rear their heads when man and nature collide. AIDS is believed to have originated in chimpanzees in remote Central Africa and passed to humans when logging roads opened the interior to hunters who were infected while butchering their game. An outbreak of Nipah virus a few years ago in Malaysia has similar roots: fruit bats driven from the forest by logging and farming operations infected the drinking water of pig farms. The virus mutated; the pigs passed it on to humans, killing 105. Experts now believe that SARS mutated from a virus found in civet cats, a small game animal related to the mongoose found in southern China.

Until recently these rare incidents of animal-to-human disease transfer, known as zoonosis, would have occurred anonymously, deep in the jungle or other remote regions with little consequence beyond the infected individual and his immediate family or tribal group. But with global travel occurring with an ease and rate unimaginable just a few decades ago, an outbreak anywhere in the world puts the world’s population at risk. “We’re at the point where it’s not about preventing [the disease], it’s about containing it and controlling it once it has appeared,” Hartstein says.

ome experts warn that the right confluence of events could create a kind of epidemiological “perfect storm”—a disease so virulent, so contagious, and mutating with such speed that the resulting pandemic would be impossible to avoid. If such an event occurs, clinicians and researchers at the School of Medicine’s Division of Infectious Diseases will be among the first drafted to help contain it. The school’s stature in the field is rooted in exposure to both variety and volume. “You can definitely expect to see a broader spectrum of diseases in a city like Miami. This has helped us gain the kinds of experiences that few other hospitals can provide,” Gwendolyn Scott says. Indeed, the school’s prominence in AIDS research and treatment is a response to a local patient population with one of the nation’s highest rates of HIV infection. The same is true of its much-lauded Sexually Transmitted Diseases program

To illustrate the fury of a worldwide pandemic, epidemiologists point to the 1918 influenza outbreak that killed an estimated 20 million people, including about 670,000 Americans. And that was at a time when transcontinental travel was rare. As SARS demonstrated, an isolated outbreak can make its way around the world in a matter of weeks. But according to Baracco, the chance of a 1918 repeat is low. While there is little doubt that new diseases will appear, advances in communications have allowed public health officials to construct an early warning system. “One person may get sick of a mysterious disease in remote Africa and we’ll know about it within days, even hours, all across the globe,” he says.

Similar advances have occurred in the field of medical sleuthing: epidemiologists often can isolate a previously unknown pathogen within days of an outbreak. Baracco, who also heads the infection control committee at the Veterans Administration Medical Center in Miami, says health care officials are more prepared than ever to prevent disease transmission. Following the SARS outbreak, for example, new procedures were adopted at the hospital to better detect potential cases. Among the changes: requiring all patients with fevers or coughs to wear masks, even before diagnosis; questioning incoming patients about recent travel histories; and immediately isolating suspected disease carriers.“ SARS has shown us that with proper precautions we can respond to an outbreak of disease, even ones we know very little about,” says Baracco. “But we always have room to improve our preparedness. After all, there’s no question we’ll be seeing more and more of these outbreaks no matter what we do. There are going to be mild ones and there are going to be bad ones. The important thing is to be ready when they arrive.”