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Testimony on Eradication of Infectious Diseases by Claire V. Broome, M.D., M.P.H.
Acting Director
Centers for Disease Control and Prevention
U.S. Department of Health and Human Services

Before the House Committee on International Relations
May 20, 1998


Good morning. Mr. Chairman and members of the Committee, I want to thank you for your invitation to testify at this important hearing on plans to eradicate or eliminate seven diseases. I am Dr. Claire Broome, the Acting Director of the Centers for Disease Control and Prevention (CDC). Accompanying me today are Dr. Walter Orenstein, Director for the National Immunization Program and Dr. James W. LeDuc, Associate Director for Global Health, National Center for Infectious Diseases. Today, I will briefly address issues related to CDC and global disease eradication and elimination programs:

  • The rationale for supporting global disease eradication initiatives,

  • Progress towards global polio eradication,

  • Progress towards global measles control and eradication,

  • Guinea worm eradication, and

  • Diseases that the World Health Organization (WHO) has targeted for elimination: lymphatic filariasis, onchocerciasis, Chagas' disease and leprosy.
RATIONALE FOR GLOBAL ERADICATION INITIATIVES

CDC defines eradication as the permanent reduction to zero of the worldwide incidence of infection caused by a specific agent. Eradication occurs with deliberate efforts and creates an environment where intervention measures are no longer needed. Elimination, on the other hand, is defined as the reduction to zero of the incidence of infection in a defined geographic area. Elimination also occurs through deliberate efforts, but, unlike eradication, intervention measures are still required because the agent still exists elsewhere and could be imported. The CDC participates in eradication programs as a result of public health, economic, humanitarian and other reasons. Diseases do not recognize boundaries. Therefore, international disease elimination and eradication activities are essential in protecting Americans from the threat of imported disease. Although the United States has been free from endemic polio since the early 1970s, polio cases resulting from imported polio virus occurred in several years in the late 1970s and 1980s. Virtually all measles cases in the United States are now directly or indirectly imported from other countries. By contrast, no American has suffered from smallpox since global eradication was reached in 1977.

Successful eradication programs save significant amounts of money. The eradication of smallpox in 1977, with support from the CDC and the U.S. Agency for International Development (USAID), proved to be a remarkably good economic investment. A total of $32 million was spent by the United States over a 10-year period in the global campaign to eradicate smallpox. The entire $32 million has been recouped every 2 months since 1971 by saving the costs of the smallpox vaccine, administration, medical care, quarantine and other costs. According to General Accounting Office (GAO) estimates from a draft report, "Infectious Diseases: Soundness of World Health Organization Estimates to Eradicate or Eliminate Seven Diseases," the cumulative savings from smallpox eradication for the United States is $17 billion. The draft report also estimates the real rate of return for the United States to be 46 percent per year since smallpox was eradicated.

Achievement of global polio eradication will offer benefits similar to those realized by smallpox eradication. More than $230 million will be saved annually in the United States alone in polio vaccine and administration when polio eradication is achieved. Globally, more than $1.5 billion will be saved annually.

Disease eradication also dramatically reduces the global burden of disability and death resulting from disease. Smallpox eradication eliminated the suffering of an estimated 10-15 million people a year and saved the lives of 1.5 million people per year. The polio eradication initiative is eliminating the burden, disability and death related to polio. Already, several million children worldwide are NOT paralyzed because of the dramatic reductions in polio virus transmission. About 10 percent of the children who contracted paralytic polio would have died as a consequence of the disease without the global polio eradication initiative.

Successful disease eradication initiatives also benefit the broader spectrum of public health. These benefits include:

  • Disease surveillance systems established for eradication initiatives can be used for other important public health efforts. For example, polio surveillance systems in Latin America were helpful in determining the scope of cholera outbreaks in the early 1990s.

  • Eradication initiatives provide models for appropriate and feasible laboratory networks. For example, the global polio laboratory network (87 virology labs) developed for polio eradication is a model for global infectious disease laboratory surveillance.

  • Capacity building required for successful eradication initiatives leads to improvements in planning, training, and communications.

  • The global polio eradication initiative has helped expand the computer capacity and demand for technological advancements in developing countries.

  • The success of polio eradication activities increases the enthusiasm for immunization and other public health programs by local and political officials.

Recent Congressional hearings have examined the benefits of global infectious disease eradication efforts. On March 3, 1998, the Senate Committee on Labor and Human Resources, Subcommittee on Public Health and Safety, held a hearing highlighting issues surrounding the global burden of infectious diseases. Senator Bill Frist, Subcommittee Chairman, noted that the United States must be concerned about the threat to its citizens by the spread of infectious diseases. Dr. David Brandling-Bennett, M.D., Deputy Director of the Pan American Health Organization (PAHO), testified that the United States must not fail to complete the "unfinished business" of eradicating or eliminating diseases which have already been targeted by the international community. At an April 23, 1998, hearing on combating infectious diseases, held by the Senate Committee on Appropriations, Subcommittee on Foreign Operations, Subcommittee Chairman Mitch McConnell noted the need "to invest in a serious, sustained global commitment" toward these issues.

The CDC believes that diseases selected for global eradication should be few in number and carefully identified according to accepted criteria. Specific factors must be considered before the global community embarks on eradication initiatives:

  • Biologic feasibility of eradication -- are humans the only reservoir for the disease?

  • Burden of disease, disability and death

  • Availability of an effective, practical intervention (e.g., drug, vaccine, etc.). Ideally, the intervention should be safe, inexpensive, long-lasting and easily deployed

  • Cost-effectiveness of eradication versus ongoing control

  • Operational and technical feasibility of implementing eradication strategies

  • Global capacity for political, financial, managerial and technical support needed for a worldwide initiative

Although disease eradication initiatives provide compelling benefits, the world would be poorly served if more eradication programs were launched than the global health community could properly manage or support. Launching eradication initiatives which do not meet the accepted criteria would be equally harmful.

PROGRESS TOWARDS GLOBAL POLIO ERADICATION

Extraordinary progress continues towards achievement of the goal of global polio eradication by the year 2000. Reported cases have declined by 90 percent since the initiative was launched in 1988. All countries of the Americas have been polio-free since 1991, and virtually all countries in Europe and the Western Pacific Region (including China) have been polio-free for one or more years. More than 400 million children worldwide were vaccinated against polio in National Immunization Days (NIDs) in 1997. Over the course of the polio eradication initiative, several million children and families have already been saved from the ravages of paralytic polio.

The polio-endemic countries of middle and south Asia, including India, Bangladesh, Myanmar, Nepal and Indonesia have conducted NIDs for 2 or more years. More than 150 million children were immunized in India and Bangladesh alone. India's new National Polio Surveillance Project works with a national laboratory network and has greatly improved India's surveillance during the last six months. Current efforts to eradicate polio involve continuing Polio NIDs, improving polio surveillance, and strengthening routine immunization programs.

Collaboration among Rotary International, WHO, UNICEF, USAID, CDC and the governments of Australia, Denmark, Japan, United Kingdom, and other countries has been unique among public health initiatives for the unprecedented level of cooperation, the scale of private sector contributions and the amount of funds raised. It is estimated that Rotary International will have contributed more than $400 million by the end of the polio eradication initiatives. Rotary International's contribution is the largest private contribution to a public health initiative in history.

Despite the extraordinary progress towards polio eradication, progress in Africa has not kept pace with progress in other regions. Rapid and complete implementation of the recommended polio eradication strategies is urgently needed. Completion of special initiatives in war torn areas such as Somalia and Sudan is essential to bringing the polio eradication program to a successful and timely conclusion. Additional funding from donor organizations and governments will be required to support polio eradication activities in Africa. Despite the many challenges presented by Africa, CDC remains optimistic that polio will be eradicated by the end of the year 2000.

The primary legacy of polio eradication will be the disappearance of a devastating disease that acted as a scourge on our children. But that is not all. The polio eradication program will leave stronger immunization programs worldwide, improved capacity for disease surveillance, a functioning global laboratory network and the momentum to tackle other major public health problems, including measles.

PROGRESS TOWARDS GLOBAL MEASLES CONTROL AND ELIMINATION

Despite the availability of a highly effective vaccine, measles is one of the greatest causes of illness and death worldwide. Measles causes 1 million deaths annually and accounts for more child deaths than any other vaccine-preventable disease. One out of every 10 children less than 5 years old who dies today will die from measles, a preventable disease. Virtually all cases of measles in children in the United States are now the direct or indirect result of measles imported from Europe, Asia and Africa.

Global measles eradication would result in economic benefits for the United States. The CDC estimates that more than $50 million annually in measles vaccine costs alone would be saved in the United States following a successful measles eradication initiative. Additional savings would accrue from the prevention of hospitalizations and medical costs if future measles epidemics in the United States were eliminated. For example, hospitalization and other medical costs exceeded $150 million during the measles resurgence in the United States from 1989-1991.

WHO is considering a global measles eradication initiative as a result of the global interest in ending the sickness and death caused by measles. Although there is not yet consensus for a global measles eradication initiative, CDC fully supports regional measles elimination goals and accelerated measles control as a step towards a global eradication initiative. If regional measles elimination goals continue to be successful, CDC hopes that a global measles initiative will be launched as the polio eradication program comes to a successful conclusion.

A tremendous amount of progress towards establishing a global measles initiative has already occurred. In 1994, the Pan American Sanitary Conference endorsed the goal of measles elimination in the Western Hemisphere by the year 2000. Implementation of an immunization strategy combining high routine coverage with at least one dose of measles vaccine and periodic mass campaigns vaccinating all children in target age groups regardless of prior receipt of measles vaccine has led to a greater than 90 percent reduction of measles cases in the Western hemisphere from 1990 to 1997. Measles transmission has been interrupted in the Caribbean and most countries of Central and South America for more than one year. Mexico, Argentina, Colombia, Chile, Peru, and all of the Central American countries and the English-speaking Caribbean have demonstrated that measles transmission can be interrupted for one or more years. The importation of measles into the United States from countries in Latin America has virtually disappeared. In addition to the ongoing measles initiative in the Americas, the Eastern Mediterranean Region of the WHO has established a regional measles elimination initiative, the European Region is considering one, and several African countries have established national measles elimination initiatives.

Many experts have concluded that global measles eradication is biologically feasible, and appropriate based upon fulfilling criteria agreed upon by public health experts. However, the eradication of measles will be a more difficult challenge than either polio or smallpox eradication. The high infectiousness of the measles virus and the complex logistical and operational requirements for measles eradication make this a unique challenge. Increased funding, technical support, and coordination will be needed for a measles eradication initiative. Another major challenge will be harnessing the political will globally to move forward. This is particularly relevant for many developed countries in Western Europe and Asia that have not accepted measles as a serious health burden and thus have not made prevention of measles a high priority.

Refinement of the technical strategies (e.g., vaccination, surveillance) for measles eradication may also be needed. Although we have achieved a tremendous amount of success with measles elimination, outbreaks still occur. In 1997, a measles outbreak in Brazil affected more than 20,000 individuals, primarily young adults. Investigations are ongoing to determine the reasons for the outbreak and what additional prevention strategies may be required for adults. CDC supports the rigorous evaluation of ongoing Regional measles elimination initiatives.

Despite the importance of measles as a public health problem in the United States and worldwide, it is critical that the global public health community focus on finishing polio eradication before embarking on a more difficult and expensive measles initiative. As we continue our efforts to eradicate polio by the year 2000, we are carefully considering how we can best achieve global measles eradication.

DRACUNCULIASIS (GUINEA WORM)

Another disease nearing eradication from the world is dracunculiasis, or "Guinea worm", once responsible for an estimated 10 million infections across much of Africa and extending into Pakistan and India. Dracunculiasis is a parasitic disease that affects children and adults, causing severe disability resulting from the emergence of a worm, approximately 3-foot long, from the skin. It prevents farmers from planting their crops, nursing mothers from caring for their infants, and children from attending school. It does not occur in the United States, and Americans almost never come in contact with it. Rather, it attacks the poorest of the poor in affected countries and further robs them of their ability to help themselves. It is transmitted in contaminated water, and it can be prevented by providing safe drinking water from wells or by educating people about the disease and how to filter their drinking water through cloth filters.

Since the early 1980's, CDC has worked closely with the Carter Center and WHO to provide the scientific underpinnings for this program and to translate the science into practical operations manuals to guide local implementation of interventions. The success of the global campaign to eradicate Guinea worm is a tribute to President Jimmy Carter and the dedicated staff of the Carter Center, who have made this one of their primary missions. Due in large part to their efforts, in collaboration with WHO, CDC, and other partners, dracunculiasis has been eliminated from India and Pakistan and is on the verge of elimination in 5 of 16 endemic countries in Africa. Moreover, incidence of the disease has declined from an estimated 3.2 million cases annually in 1986 to less than 80,000 cases in 1997, most of them in southern Sudan, where civil conflict has prevented the introduction of effective interventions. Outside of Sudan about 35,000 cases were reported to WHO in 1997.

The date when Guinea worm will finally be eradicated depends on access to war-torn regions of some affected countries, but there is general agreement that the end is in sight, and this disease should be eradicated soon after the turn of the century, given continued support to the eradication effort.

LYMPHATIC FILARIASIS

I will now briefly discuss the four diseases that WHO has targeted for elimination, rather than eradication, beginning with lymphatic filariasis. Recent technical advances coupled with the generous donation of drugs to treat lymphatic filariasis have led to encouraging discussions that this disease may eventually be a candidate for global eradication. Lymphatic filariasis is a mosquito-borne parasitic disease that infects an estimated 120 million people in India, elsewhere in Asia, Africa, many Pacific Islands, the Caribbean, and South America. This infection causes gross disfiguring enlargement of the legs, arms, or genitals in approximately 40 million of those infected. The good news is that an effective drug combination has been found that is 99 percent effective against the parasite that causes lymphatic filariasis, and the manufacturer of one of these drugs, SmithKline Beecham, has agreed to provide the drug free of charge to WHO for use by governments and other organizations in their elimination campaigns.

CDC works with WHO to eliminate lymphatic filariasis primarily through our WHO Collaborating Center for Control and Elimination of Lymphatic Filariasis, which is located within CDC's National Center for Infectious Diseases. CDC staff are working closely with experts from around the world to design and implement national campaigns, applying the lessons learned from our active research and control efforts. CDC is also carefully evaluating the effectiveness of new drug combinations in eliminating transmission of the parasite.

It is too early to accurately estimate the required time to eradicate lymphatic filariasis or the eventual cost, but given the generous donation of drugs already made, it is clear that significant progress will be seen in the years ahead.

ONCHOCERCIASIS (RIVER BLINDNESS)

A similar parasitic disease, onchocerciasis, is also vector-borne, although transmitted by biting flies rather than mosquitoes. About 18 million persons are infected in Africa and parts of the Americas and the Middle East. The infection leads to blindness; since the vector flies breed in rapidly flowing water, the disease is found near rivers, thus the origin of the common name for this infection, "River Blindness." Prime farming land near rivers in Africa and Latin America has gone uncultivated for fear of the disease. Over the last quarter century, WHO and The World Bank have led an effective vector control program to fight River Blindness in West Africa, and today much fertile land is now yielding valuable crops, demonstrating the success of a campaign that has eliminated this infection as a public health problem from 11 countries. Since 1987, the generous donation of the drug ivermectin (MectizanR) by Merck and Company has now led to efforts to control the disease by treatment of affected populations with a single oral annual dose of the drug. Since 1991, a campaign in the Americas to eliminate onchocerciasis as a public health problem has led to treatment programs in all six affected countries: Mexico, Guatemala, Brazil, Colombia, Venezuela, Ecuador. In 1995, the World Bank and WHO launched another campaign to expand treatment coverage to all parts of Africa where the disease still is uncontrolled. As with Guinea worm efforts, CDC has worked closely with the Carter Center and WHO/PAHO to provide the technical assistance and scientific backup needed to help guide implementation of interventions. In addition, our field station in Guatemala serves as a central coordinating facility for identifying endemic foci in Central America and targeting control activities.

Global eradication of onchocerciasis is probably unattainable given the difficulty of sustaining once-a-year treatment for at least 10 years and questions about whether once-a-year treatment will be frequent enough to interrupt transmission of the parasite in all settings. Research is underway to address these technical and logistical issues. Despite these challenges, elimination of the infection is imminent in at least four of the six affected countries affected in Latin America, and in the Middle East. In addition, complete and sustained implementation of ivermectin delivery can result in complete control of this infection in Africa.

CHAGAS' DISEASE

A third vector-borne parasitic disease considered in the GAO report is Chagas' disease. This disease is found only in the Americas where it is transmitted between animals and to humans by insects commonly called "kissing bugs". Several different insect species are able to transmit the parasite, but in the southern half of South America, only a single species is important in the transmission cycle to humans. PAHO has targeted elimination of Chagas' disease throughout broad regions of South and Central America, focusing on insect control. These efforts began in the southern cone region, such as Argentina, Uruguay, and Chile, where considerable success has been attained. Two additional programs have recently been launched to include the Andean region and Central America. While we do not believe eradication is a real possibility given today's tools, control in well-defined areas like the southern cone nations is a practical goal. CDC is working closely with PAHO and the member nations of the three control initiatives to provide tools and resources for improving control strategies and evaluating program success.

HANSEN'S DISEASE (LEPROSY)

Leprosy is the final disease targeted by WHO for possible elimination. Leprosy, a bacterial disease known from biblical times, usually affects the skin and peripheral nerves, but has a wide range of possible clinical manifestations. In 1997, there were an estimated 1.15 million cases in the world, most of them concentrated in South-East Asia, Africa, and the Americas. Each year, approximately one-half million new cases are detected worldwide.

Current efforts to eliminate leprosy focus on a combination of identifying infected patients and sustained treatment using a highly effective multi-drug regime. Leprosy is usually spread from person to person; however, once treatment begins, patients cease to be a source of infection for others. The leprosy infection can be cured within 6 months to 1 year.

There are fewer than 1000 cases of leprosy recognized in the United States, almost all of which are under active multi-drug therapy. The disease remains relatively common in the Republic of the Marshall Islands and the Federated States of Micronesia, which have compacts of free association with the United States. These two areas have prevalence rates that are among the highest in the world.

WHO has taken the lead in the global leprosy elimination campaign, and CDC has had relatively little involvement to date in this campaign. However, CDC, along with the Gillis W. Long Hansen's Disease Center of the Health Resources and Services Administration, is exploring collaborations with the Ministry of Health and Environment of the Republic of the Marshall Islands to reduce the burden of this disease.

CONCLUSION

The potential public health, financial and humanitarian benefits of eradication programs offer a compelling rationale for U.S. Government support of such initiatives. The smallpox eradication program and the ongoing polio eradication initiative best document that these potential benefits can be realized. However, the United States must continue to carefully evaluate prospective elimination and eradication programs to ensure that they are selected based on accepted scientific, programmatic and economic criteria. We must ensure that the global public health capacity to support such initiatives exists or can be developed. Recognizing appropriate causation, the United States must also be willing to be ambitious and far sighted, even when some questions remain unanswered. The health of our children and the world's children is far too important to allow continuing paralysis or death from diseases which can be prevented forever by a simple vaccine.


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