By Tonie Auer
November 25, 1999
Photo: Digital World

When a strain of encephalitis never before seen in the United States killed six people in New York last August, both health officials and the public got worried.

The outbreak raised questions officials are still trying to answer, such as how the virus got to the United States and what they can do to keep it from happening again. It’s also drawn attention to issues public health officials have been working on for years, such as how infectious diseases are transmitted from one country to another and how travel, food handling, and environmental change affect the problem.

The root of all illness

While it might seem that infectious diseases are a problem of the past, they still put an incredible burden on society. Modern advances such as antibiotics and vaccines have helped conquer some diseases, but new ones—such as AIDS, Lyme disease, and hantavirus pulmonary syndrome—are always emerging and often spread from one country to the next.

Increasing international airline travel could be a big part of the problem, experts say. “Someone in the U.S. can be in Australia in a day, and that is—often—less than the incubation time of a disease. When that person returns to the U.S. and gets sick here, the doctor wouldn’t know what is occurring,” said Jeff Taylor, MPH, epidemiologist with the Bureau of Communicable Disease Control for the Texas Department of Health.

Changes in the food supply, such as mass production and global distribution, have made hundreds of thousands of people ill. “Disease is spread faster today than in years past because of the mobility of people, among many other reasons, as well as the number of people who eat out,” said Caryl Collier, MPH, RN, chief of the Office of Communicable Disease, Consultation, Quality Improvement, and Training for the Missouri Department of Health. For example, changes in the way food is grown, as well as food packaging and distribution systems, have led to the potential for rapid spread of foodborne pathogens such as E. coli, which has continued to surface in industrialized countries, said Joan Dzenowagis, PhD, a scientist with the Division of Noncommunicable Diseases of the World Health Organization.

Another important factor in the spread of disease is environmental change, said James M. Hughes, MD, director of the National Center for Infectious Diseases. Many emerging or reemerging diseases are acquired from animals and insects like mosquitoes, ticks, and mice, and environmental changes like global warming can alter the habitats of organisms that transmit disease.

Keeping an eye on things

Strong surveillance programs are an important part of controlling the spread of disease, officials say. “While we cannot expect to totally prevent the migration of viruses from one part of the world to another, our best efforts should, and do, concentrate on strong surveillance for early detection and response, well-equipped labs, and a cadre of public health officials trained and equipped to confront and control viruses,” Hughes said.

Evaluating and investigating outbreaks is more precise when sensitive surveillance systems are in place, Collier said. Alert health workers, such as nurses in community clinics or emergency rooms, also play a key role in stopping the spread of disease, Dzenowagis said.

“Reports of unusual numbers and patterns of disease in a population can alert health officials to pay attention to these patterns and step up monitoring or to launch an investigation in order to determine what containment measures should be put in place,” Dzenowagis said. “We really depend on reliable information and reporting systems to catch unusual disease events, which can then lead to action.” That action can be as simple as educating the public about how to prevent the disease or stressing the importance of vaccinations, experts say.

Strengthening infectious disease surveillance and response, as well as improving methods of gathering and evaluating surveillance data, is critical not only for detecting outbreaks, but also for improving public health practice and treatment, Hughes said. “The public health infrastructure is the underlying foundation that supports the planning, delivery, and evaluation of public health activities and practices,” he said.

Ultimately, despite episodes like last summer’s outbreak in New York, public health officials say they are largely prepared for future outbreaks. “Certainly no system can guarantee that diseases can be contained,” Dzenowagis said. “But the systems in place in many industrialized countries have gone a long way in reducing the toll of infectious disease through prevention and prompt diagnosis and treatment where needed.