Dispatches - Spring 2002
A. Tassy Prosser and Nathan Wolfe
Out in the Cameroon bush, a hunter from the village has had a good day. He heads back to camp carrying a freshly killed duiker, a kind of small antelope, in a rattan sling on his shoulder. Blood from the animal drips down the hunter's bare legs, which are scratched and cut from his trek through the underbrush. At the camp, his wife takes the game and butchers it, accidentally cutting herself on the sharp knife in the process.
Later, she will smoke the strips of meat over an open fire, and, once preserved, the duiker will be sent by bus to the capital city of Yaoundé. The exchange is part of an extensive underground economy that provides forest game — bush meat it is called — to the country's urban centers in exchange for cash.
It is exactly this process that research associates Nathan Wolfe, ScD, an infectious disease expert, and his wife A. Tassy Prosser, MS, an anthropologist, have been carefully studying. The post-docs, working under Professor Don Burke, have come to west Central Africa to try to discover how new diseases enter the human population. In particular, they are interested in how the hunting and butchering of forest animals - including monkeys and even apes — could be a mechanism of transmission enabling new pathogens to enter into the human population.
"I'm interested in a whole range of diseases, especially the ones that may have the potential to move from animals into humans but have not yet done so to our knowledge," says Wolfe. "Just one example would be the simian hemorrhagic fever virus, which is known to exist in nonhuman primates and is just the sort of virus that could be an important emerging agent." It is thought that Ebola and HIV and perhaps a number of other viral infections may have entered the human population through just this process — blood-to-blood contact between animal and human during some step of hunting, butchering, or consumption.
Wolfe and Prosser spend part of their time in the field, observing how bush meat is butchered and distributed. More often, they are visitors to the bush villages where they oversee AIDS testing, awareness, and education programs while collecting extensive behavioral data about the lifestyles and activities (including hunting and butchering) of the residents. Prosser oversees a team of four counselors who can ask questions in either French (the language of Cameroon's colonial heritage) or one of several local languages such as Ewando, Douala, or Fang. "What I try to do is ensure the accuracy of questionnaire results and then compare them with the blood test results," says Prosser.
The blood tests themselves enable Wolfe to conduct what he calls "sero-archaeology," the careful examination for trace evidence of exposure to new and different viruses. "We're looking for retroviruses in general," he says. "This includes a whole range: HIV and other closely related viruses, HTLV, foamy viruses, and others."
The scientists' research has already turned up one disquieting discovery. "What has been an eye-opening experience is just how wide-scale this practice is," says Prosser. "Cameroon is 50 percent urban at this point, but there is a lot of anxiety about that urbanization. Ask almost anyone, and he will tell you he is 'still a villager at heart.' Often, the way urban dwellers maintain that connection is by eating bush meat, so there is large-scale consumption of bush meat in the cities, even though it costs more there than chicken or beef."
Although consumption of bush meat is officially discouraged—and even illegal—the Cameroon government has not been able to put an end to the practice. If this black market economy leads to the introduction of new infectious agents into human populations, success in battling them will depend to a large extent on how quickly they are identified. "Currently, we wait for an epidemic to start before we mobilize resources to fight it," Wolfe says. "What we want to try to do is create a science that is predictive, that identifies the mechanisms that enable new diseases to appear. What we're trying to do is create the science of emerging disease."
After a lifetime of public service, Luis F. Duque settled down several years ago to enjoy retirement in his Medellin home. The public health professor and former rector of the University of Antioquia once served as Colombia's deputy minister of health and director of the Colombian National Institute of Health in Bogota. Later, he was an adviser on health policy to the nation's president. Duque, MD, MPH '68, was ready to relax and pursue his passion of reading, good discussion with his wife and friends, and great music (both classical and Colombian).
But lately he's been employing the tools of public health to help bring about an end to the plague of violence that has traumatized Colombian society for the past several decades. Call it a semi-retirement.
Now a senior adviser to a nascent violence prevention program at the University of Antioquia's School of Public Health, Duque and his colleagues are planning a new effort to apply science to the understanding and control of deadly human passion.
"Violence has been the leading cause of death in Colombia for 15 years," Duque says of his country's extraordinary murder rate. "Fifty percent of healthy years of life lost in Medellin are lost through homicide. That loss is equal to the amount of healthy years lost to all other causes. We're just starting to research into why this is so."
Although the country has been engaged in an on-again, off-again civil war with insurgent groups such as the Fuerzas Armadas Revolucionarias de Colombia (FARC), Duque maintains that only about a fifth of the nation's violent deaths are the result of armed conflict. "Eighty percent of the problem is everyday violence such as criminals with handguns," he says. "Our murder rate is not a political problem, it's a public health problem."
Last year, about 4,000 people were murdered in Medellin, a city of more than 2 million. "Currently, the murder rate in Medellin is 180 homicides per 100,000 people," Duque says. "That compares with a rate of 40 to 50 per 100,000 in Bogota, and between 10 and 12 for the United States." About 90 percent of the violent deaths are from guns, a change from two decades ago, when only about half of all murders involved firearms.
"Clearly, alcohol, psychotropic drugs, and the availability of guns all play a role," Duque says. "But these are factors I would label instrumental. I don't think that the guns by themselves are the cause."
Rather, he cites a culture mired in profound social and economic inequity, a mass media both domestic and international that seems to glorify violence and vigilantism, and an erosion in traditional cultural values. Great changes in the family and educational system, he believes, have created the cultural and social conditions that have made possible the narcotics traffic that has brought Medellin worldwide attention.
"Now there is a crisis in values," he says. "We need to rebuild the societal values structure starting from some basic values, which can be accepted by the community as a whole."
There are signs of improvement. In the past decade, Medellin's murder rate has been cut in half. Duque hopes the university's new program in violence prevention will help further such progress. But with the city's unemployment rate at 20 percent, crime is an ever-present fact of life, particularly among the city's poor. "Our challenge is to work with children and young people to create a new cohort in society that works out its differences without resorting to violence," says Duque.
Tracking anthrax attacks in New York was the job that took Els Mathieu (MPH '00) into the eye of a media hurricane. But the 35-year-old Belgian says it was a fairly routine outbreak of cryptosporidium in rural Ohio that really gave her an insight into the American system of public health, and how it differs from those in Europe.
An Epidemic Intelligence Service officer in the National Center for Infectious Diseases of the Centers for Disease Control and Prevention in Atlanta, Mathieu must be ready to leave at short notice to investigate infectious disease outbreaks in the United States. When more than 700 people in a small rural town outside Columbus came down with diarrhea and other symptoms typical of crypto, Mathieu was sent as the primary investigator.
"I began working with the local health department, and I learned that the local voters had to vote to approve their budget," says Mathieu. "Essentially, they [the health department] had to compete for their funding with other departments. I found that quite sad that people don't see [public health] as necessary." In Europe, she observes, the public health infrastructure is mandated and maintained by the national government.
The cryptosporidium was quickly traced to a community swimming pool and the outbreak was soon contained. But she thinks the area residents came away with a heightened appreciation of the need for an effective public health infrastructure, in much the same way the anthrax attacks made that point on a national scale.
It's been nearly 60 years since Johns Hopkins physician and researcher Leo Kanner first described autism. A pervasive developmental disorder generally diagnosed when children are young (between 18 months and 5 years of age), autism is characterized by absent or delayed language skills, profoundly hindered social interactions, and oftentimes rote and repetitive behaviors. Both the etiology and epidemiology of autism are poorly understood. For decades, the neurobiological disorder was thought to be rare — somewhere on the order of 5 cases per 10,000 people. But in recent years that number has been going up, raising speculation and concern that autism is becoming more prevalent.
"Researchers are leaning today toward a prevalence estimate of 10 to 30 cases of classic autism per 10,000," notes Craig Newschaffer, PhD '96, assistant professor of Epidemiology. In addition, he says, perhaps two to four times that number fall within the range of Autism Spectrum Disorders, or ASD, in which some of the behaviors of classic autism are not present, or occur in a milder form. No one knows if these increased numbers, which are substantially higher than the estimates of 25 or even 10 years ago, reflect increasing risk or simply better diagnosis and reporting. Newschaffer hopes to find out.
In October the School announced the creation of the Center for Autism and Developmental Disabilities Epidemiology, or CADDE, with Newschaffer at its head. One of four such Centers of Excellence for the study of autism funded by the Centers for Disease Control and Prevention (CDC), it is the only one focusing on the interaction between genetic and non-genetic factors and their possible link to autism. The CDC has committed more than $2 million over the next five years to CADDE, which will enable Newschaffer and other researchers to conduct an extensive surveillance project in the Delaware/Maryland area to better estimate ASD prevalence. CDC funding will also support a large multi-site, case-control study in which CADDE will focus on possible links between ASD, genes that influence immune response, family history of autoimmune disease, and prenatal infections. In addition, the Center will serve as an information resource for parents, physicians, and other researchers.
"If there has been a real change in ASD risk over a relatively short period of time, that suggests there is some non-heritable component involved somehow in the disorder," Newschaffer says. CADDE will undertake to identify a likely culprit. But what that component might be, and how it relates to an individual's genetic susceptibility to autism, is unclear. Autism is known to have a large heritable component, yet despite a decade of intense search for the gene or genes responsible, "we still don't understand the underlying causes."
Genes and environment are a potent mix in human health, as researchers in cancer have come to learn. Newschaffer began his own career in cancer epidemiology, a background he says may prove uniquely useful. "In cancer epidemiology we acknowledge this gene and environment interaction," he says. "It strikes me that the tools developed there could be successfully applied to autism."
He might have stayed with cancer research, had not his first child, Jonas, been diagnosed with autism while a toddler. "He was behind in language development so we were having his hearing tested," Newschaffer recalls. "At a party a pediatrician friend saw him and suggested that the problem might be something other than hearing loss." Jonas is now 9. "It took a few years for me to decide that I wanted to move into autism research," Newschaffer says. "There were few epidemiologists at work in this field. I saw a real need for population-based approaches. I want to help try to get a handle on these apparent trends."
Gansu Province, China
High in the mountains of Gansu Province in China's northwest, Christy Fong (MPH '99, PhD candidate in International Health) is at work tracking down a familiar killer. In her efforts she relies upon the project's jeep, a skillful driver who knows the unmarked roads and local language, and a steely sense of determination. "I'm here because of my passion for helping my country's poor and ethnic peoples," she says.
Despite tremendous advances in the control of infectious diseases made in the 1950s and '60s, China still battles one of its most persistent and deadly foes: tuberculosis. "TB was rampant in the 1930s and '40s , and was one of the primary killers in China,"
Fong says from her office in Linxia City, China's "Little Mecca" and home to some 800,000 Muslims. "In the early days of the People's Republic there was a strong effort to control TB and other infectious diseases that was very successful. But then the emphasis moved to other health issues and economic development, and in recent years, with the great increase of inter-province migration, the frequency of transmission of TB has increased significantly." In addition, China has become one of the world's 'hot spots' of emerging drug-resistant TB strains."
Fong is a health technical consultant for a TB control project sponsored by World Vision, an international Christian relief and development organization. She is helping initiate the TB program among the Muslim Dong Xiang ethnic minority, a group that has suffered a high prevalence of TB for many years. In particular, she is working to bring improved TB care to the women of the district, who have typically been disadvantaged by lower educational levels, language barriers, social customs, and remoteness, all of which have limited their access to government tuberculosis services.
Half of Fong's time is spent crisscrossing Dong Xiang County, visiting women TB patients in their homes to collect information and monitor adherence to the 6 to 8-month treatment regimen that involves four or more TB drugs. The other half she spends directing the project and training local health workers. The project's five-township target area is largely semi-arid and mountainous, ranging in elevations from 2,000 to 3,000 meters, and houses tend to be scattered at great distances. Fong is battling tuberculosis one case at a time, while organizing a community-based effort to create a sustainable program of TB control.
"What we are trying to do is enable these patients to become change agents in their communities," she says. "Other people will tend to listen to the experience of patients who have been cured. By this we hope to create a rippling effect that will amplify our efforts throughout the county."