Heymann D.

Publication Details


Emerging infectious diseases are closing, or have the potential to close windows of opportunity for infectious disease eradication or elimination. The 20th anniversary of the eradication of smallpox provides a reminder of an opportunity of which the world took advantage. Smallpox had been a devastating disease with high transmission and case-fatality rates. In 1969 alone, smallpox caused 1.6 million deaths. The eradication of smallpox stands as one of the outstanding achievements in the history of public health. Eradication was achieved because of a worldwide effort that was supported by the necessary political will and human and technical resources. The world took advantage of opportunity for smallpox eradication because a safe vaccine was available.

In the year that smallpox was declared eradicated, human immunodeficiency virus, HIV, appeared and rapidly colonized Africa and the world. Today, the prevalence of HIV is greater than 25 percent in some adult populations, such as in the Democratic Republic of Congo (formerly Zaire). In the United States, a military recruit who was immunized against smallpox developed generalized vaccinia because he was HIV seropositive, and died. That tragic event highlights the fact that if the global smallpox eradication campaign had been postponed, the world would not have been able to eradicate smallpox as easily as it did before 1980.

Many other opportunities have been lost. In the 1950s and 1960s, gonorrhea was highly prevalent throughout African countries. Governments did not attempt to change behavior to prevent transmission. Treatment either was not offered or was infrequently offered. When available, treatment for sexually transmitted diseases was many times more expensive than treatment for other diseases, especially in the private mission hospitals throughout Africa. Therefore, gonorrhea largely went untreated and disease prevalence increased to a less manageable level. Today, gonorrhea is present throughout Africa, where it causes infertility in women and where it is one of the major driving forces in the HIV epidemic, facilitating the transmission of HIV. Had effective public health education been in place in the 1960s to help change sexual behavior and had antibiotic treatment been used effectively, there would not be such a great problem with gonorrhea today. In this case, a window of opportunity to control one disease and reduce the rate of transmission and impact of a far more serious disease has closed.

The prevalence of tuberculosis (TB) and multidrug-resistant TB is increasing globally. The emergence of HIV facilitated the resurgence of TB, which provides another example of a case in which an opportunity has been lost. Global surveys show that there is a 1 percent prevalence of resistance to at least one TB drug. Multidrug treatment for TB costs between $20 and $30 for a complete cure, but treatment costs are approximately $3,000 for multidrug-resistant TB. In many places, the chance to achieve a manageable level of TB by the proper use of drugs has been lost.

The global effort in the 1960s and 1970s to eradicate malaria succeeded in eradicating malariologists, but not malaria. Today, the malaria parasite is resistant to the drugs of choice—chloroquine or pyrimethamine-sulfadoxine (fansidar), or both— because of improper treatment. Drug-resistant malaria takes longer to respond to treatment. In addition, the mosquito species that transmit the parasite are resistant to the insecticide that previously controlled them because of the improper use of insecticides and a breakdown of public health infrastructure. A window of opportunity to eliminate malaria and mitigate its impact has been lost as increasing numbers of adults are losing work and more children are dying because of the resurgence of malaria.

Many public health opportunities have also been lost because of the emergence of infectious diseases. Poor public health practices by the local hospital workers in Kikwit, Zaire, drove the 1995 Ebola hemorrhagic fever outbreak. A cycle of transmission among the patient care staff transmitted the virus to their families and additional patients. The international community learned of the outbreak in May 1995, nearly 20 weeks after the first case was reported. Poor communication, poor infection control practices, and poor preventive public health measures reflect the weak public heath care systems and the poor state of infectious disease surveillance in most of Africa. With the end of the Cold War, the end of the colonial era, and the decline of Western interest in tropical diseases, the public health infrastructure in many African countries has deteriorated. Infectious disease surveillance is nearly nonexistent, and emerging infections frequently go unreported.

Immunization, the vanguard of public health practice, is losing ground in both developing and developed countries. For example, the rate of immunization against yellow fever is declining in most countries of the world, particularly those countries where the yellow fever virus is endemic. It is very difficult to have an African government commit to programs of vaccination against yellow fever as part of routine immunization programs, even though the vaccine is safe and inexpensive and engenders long-lasting immunity. In addition, tourists are becoming less and less rigorous in their vaccinations. Recently, there was an international alert when a photographer returned to Germany with an unknown disease. At first it was thought to be Ebola hemorrhagic fever, but yellow fever was confirmed to be the diagnosis.

Climate variability and climate change are closing other windows of opportunity as the distribution of some diseases is expanding as a result of changing climatic conditions. The traditional meningitis belt ran across Saharan Africa. Recently, epidemics have occurred farther south in the countries of Uganda, Kenya, and Tanzania. The spread of meningitis may be due to the extreme droughts brought about by changing climate conditions in those areas.

The bovine spongiform encephalopathy (BSE) outbreak in cows in the United Kingdom, with the subsequent resulting outbreak among humans of a variant of Creutzfeldt-Jacob disease (vCJD), is an example of carelessness in food-handling practices and public health measures. That is, in the late 1970s the procedures for rendering bonemeal and other products from animal carcasses changed. The resultant food products were used in animal feed. However, infectious agents were transmitted through the animal feed from infected carcasses back into ruminants, resulting in the BSE epidemic and the transmission of the BSE agent to humans, resulting in vCJD.

At a time when infectious diseases are on the rise—when 48 percent of deaths between birth to 44 years of age are largely due to one of six infectious diseases and when in the span of 20 years AIDS has become the second most important infectious killer in the world—the costs of treating infectious diseases are also rising. At the same time, infectious diseases are taxing economies. The 1991 cholera epidemic in Peru cost that country an estimated $770 million. The plague epidemic in India cost that country $1.8 billion. Between 1990 and 1998, BSE in the United Kingdom is thought to have cost more than $6 billion. Although, while these diseases may not be high on the list of causes of mortality, they are high on the list of causes of economic morbidity.


Among the global responses used to combat emerging infections are the International Health Regulations (IHR). The World Health Organization (WHO) administers the IHR. The purpose of the IHR is to ensure maximum security against the international spread of diseases with minimum interference in world traffic (travel and trade). The IHR ascribe a set of norms at ports of entry into countries so that diseases or their vectors, which might arrive on conveyances, do not spread beyond those port areas. At the same time, they require the reporting to WHO of any occurrence of one of three diseases: cholera, yellow fever, and plague. The IHR are limited in that they require reporting of only those three infectious diseases, even though many more infectious diseases are of equal or greater threat to human health and healthy economies. Consequently, the IHR are being revised to cover more infectious diseases and will be directed out of WHO headquarters in Geneva, Switzerland, using electronic communications for quarantine officers. The revised IHR also seek to increase the capability to report disease outbreaks and to decrease the stigma of reporting, as frequently there is a disincentive to reporting because other countries may respond by erecting trade barriers against the reporting country, such as those against countries that have reported cholera epidemics. The IHR will likely play a larger role in the future global surveillance and control of infectious diseases.

Two tools are used globally to control infectious diseases: eradication and elimination. Eradication is an important activity that has been used successfully in the past against smallpox. Current efforts to eradicate polio are nearing completion. In addition, by the end of 2001 or early 2002 it is anticipated that wild-type poliovirus transmission will be interrupted worldwide. Elimination is decreasing the prevalence of a disease to a level at which it can be more easily handled within the health care system. Lymphatic filariasis is a disease with a low mortality rate but with a high rate of morbidity and severe negative effects on local and regional economies and social structures. Efforts toward the elimination of lymphatic filariasis are under way in Africa following the guaranteed donations in perpetuity by Merck & Co. and SmithKline Beecham of the drugs necessary to control the disease. In an attempt to take advantage of the powerful partnership with the private sector, other efforts are under way to eliminate leprosy and Guinea-worm infection (dracunculiasis).

Elimination and eradication programs need a strong global surveillance system. These systems may be either formal or informal networks; both are equally important and serve a valuable role. The formal networks, such as laboratory networks, epidemiology training networks, and other groups, are networking and continuously reporting on diseases. Informal networks are often electronic discussion sites, such as ProMed and the Global Public Health Intelligence Network of Health in Canada (GPHIN). The news media, nongovernmental organizations, the Red Cross, and Doctors Without Borders (Médecins sans Frontières) are also among the many informal networks. WHO monitors the surveillance networks and validates suspected outbreaks of disease, sharing news of disease outbreaks with the global health community. Through this program, WHO identified about 215 infectious disease outbreaks between November 1996 and June 1998.


Strengthening global surveillance is not enough to eliminate or eradicate infectious diseases. Laboratories need strengthening and an improved means of communications and reporting. Networks of laboratories that link countries and regions need to be established so that appropriate actions include those people who can help the most. One means of strengthening laboratories is to work closely with those monitoring the Biological Weapons Convention. Article X of the Convention requires the signatories to exchange technologies. This effort would bring technology transfers into a coordinated program that would strengthen those signatories’ laboratories. This effort would also add to those resources that support laboratories in other countries, for few donors are interested in strengthening laboratory capacity.

Most donors are more likely to fund the “glamorous” disease control programs. However, basic public health laboratories are not strengthened. To assist with that effort to strengthen basic public health laboratories, the Center for Disease Control and Prevention is helping support diagnostic testing for meningitis and other laboratory capabilities. The U.S. Agency for International Development is also taking interest in surveillance and strengthening of laboratories.

In the future, closer ties between public health and trade organizations will be needed. Recent discussions between WHO and the World Trade Organization are exploring ways in which WHO would become an arbiter in certain trade issues with a public health component, especially in the case of infectious diseases, through IHR. Closer links are also needed in the area of food safety and IHR.

Greater collaboration is also needed between the medical and behavioral science communities. Changes in human behavior have been effective in controlling the spread of HIV in Thailand and Uganda. Yet, only those two countries have had success in this area. More time needs to be spent investigating the behavioral determinants and interventions needed for effective disease control.

The world as a whole is not putting enough effort into research and development of new vaccines. Despite several outbreaks caused by the Ebola and Marburg viruses, the global community has never been able to put together a solid research effort to discover the origins and natural histories of these viruses. Most of the investigations have been conducted with whatever funds are available at the end of a fiscal year.

Emerging infections are also requiring multisectoral approaches. For example, the world cannot address the growing problem of antimicrobial resistance among microorganisms that cause disease in humans in isolation from other sectors of society that are also involved. The fields of animal husbandry, agriculture, medicine, and public health need to work together through advocacy and public health awareness campaigns.

Creative ways are needed to secure adequate funding for infectious disease research, surveillance, and prevention programs in both the private and the public sectors. Currently, about 10 percent of health research worldwide is directed toward the needs of developing countries by both the public and the private sectors, but only 2 percent of that money is going toward the six most important infectious disease processes in those countries: AIDS, malaria, respiratory infections, diarrhea, TB, and measles. The directions of both public- and private-sector research need to be refocused back toward infectious diseases.

Emerging infections are a critical phenomenon. The globalization occurring in the world community provides a reminder of this fact. Efforts to combat emerging infections require a global response to provide adequate financial support. Public commitment needs to be developed, for where there is public commitment it will be followed by political resolve, and where there is both political and public determination there are windows of opportunity to eradicate and eliminate infectious diseases.