Gateway to World Health: Harvard Public Health at 75

by Irma S. Jarcho

The Harvard School of Public Health celebrated its 75th anniversary on 27-29 April 1997 with a wide-ranging symposium titled "Gateway to World Health: New Science and Strategies in Public Health." The three days of meetings covered virtually every aspect of modern public health, including environmental health research, health systems, health policy, the role of the state, advancing global health equity, and social relationships and health. Readers who have been interested in my reviews of such books as Laurie Garrett's The Coming Plague (Spring 1995), Maya Pines' The Race Against Lethal Microbes (Winter 1997), and Frank Ryan's Virus X (Spring 1997) would find the sessions on "Infectious Diseases and Environmental Threats" and "Emerging Diseases" of particular importance.

Tuberculosis. According to Dr. Barry R. Bloom, there is no question that the Directly Observed Therapy System (DOTS) -- seeing to it that persons infected take their medicine under the supervision of a doctor or attendant -- is effective against tuberculosis infections. But there is a limit to how extensively this can be applied where the infrastructure and the financing for such elaboration does not exist. Bloom stated that there are three things needed before we can control tuberculosis: 1) a rapid, inexpensive diagnostic test; 2) drugs that will abolish latency; and 3) an effective vaccine. Particularly impressive was a study of a series of tuberculosis patients in Harlem Hospital in 1991. Some 82% were unemployed, 79% were male, 53% were alcoholics, and 45% were homeless. Social issues in that series were as important as the disease itself.

AIDS. Dr. Myron Essex presented some of the latest statistics on AIDS infections:
location number of infections male/female ratio
North America 1.2 million 6:1
Latin America 1.5 million 4:1
Sub-Saharan Africa 19.0 million 0.9:1
Western Europe 800,000 5:1
Southeast Asia 6.5 million 2:1

As can be seen from these statistics, only in Africa does AIDS appear to be primarily transmitted through heterosexual sex. The highest rate of infection was found in Botswana, where 40% of those tested were positive for HIV.

Dr. Essex emphasized the difficulties in developing a vaccine against AIDS. The ultimate vaccine must be able to react with many strains -- HIV-1A, B, C, D, E, F, and O. In the West (U.S. and Europe) AIDS is primarily caused by HIV-1B. In Africa and Southeast Asia the other strains -- C, D, E, and A are more prevalent. To complicate matters further, HIV-2, a milder form of AIDS, appears to protect against subsequent infection with HIV-1, providing 60-70% protection.

Schistosomiasis. Professor Donald A. Horn spoke of the problems posed by schistosomiasis, second only to malaria as a parasitic infection worldwide. Up to a million people are at risk of infection, and the disease is spreading due to new irrigation projects and the construction of dams. Vaccination seems to be a possibility, and both protective peptide and DNA vaccines have been produced and are undergoing tests.

Malaria. Dr. Kamini Mendis reported that there were one to two million deaths a year from malaria, mostly in sub-Saharan Africa, where the disease caused a mortality of 5-10% in the under five group. The risk of severe malaria, highly lethal, increases with the duration of illness. The sooner treatment can be instituted, the lower the death rate.

In the session on "Emerging Diseases," Dr. Timothy Ford discussed water-borne diseases which appear to be gaining increased importance -- witness the cholera epidemic in South American and the cryptosporidosis outbreak in the United States. Possible factors in the increasing prevalence include climate change, increase in both numbers and mobility of the population, and increased pollution. Climate change effects may be seen in the apparent increase in algal blooms worldwide and a concomitant increase in pathogens associated with algal blooms. There are likewise increased reports of shellfish poisonings and fish poisonings.

Increased population translates into greater demands for water, while, in actual fact, the available supply of water per person is decreasing. Annual renewable fresh water per person in China will fall from about 4500 cubic meters in 1955 to slightly under 2000 cubic meters in 2050. In India the decrease is more dramatic -- from over 5000 cubic meters in 1955 to 1800 in 2055. In Egypt and Israel available supplies will be well under 1000 cubic meters per person.

As for cryptosporidosis, the first recorded human case was diagnosed in 1976, while the largest recorded waterborne outbreak in U.S. history occurred in Milwaukee in 1993. Dr. Ford presented an interesting classification of water-related diseases:

Dr. Mary Wilson presented some of the problems involved in confronting emerging diseases. More than 500 million persons cross international borders on commercial flights each year. In 1849 Snow demonstrated that cholera follows the major routes of commmerce. It is as true now as it was then.

Movements of the population serve to disseminate illness. In the early 1990s it was estimated that there were, globally, 20 million refugees, 30 million displaced persons (who had to move for environmental reasons, e.g., famines, flood) -- 70 million working legally or illegally in other countries, 120 million living outside their country of birth and more than 10,000 refugees within the borders of some 70 countries. With these figures, how can disease transmission be controlled?

Some current practices favor the spread of human pathogens. Giving antibiotics to farm animals to spur growth can result in resistant strains of pathogens. In the case of aquaculture the antibiotics fed to cultured fish in the ponds can be found in wild fish near fish farms.

Insects and human pathogens can survive transport. Mosquitoes, house flies, and flour beetles, placed in wheel bays of a Boeing 747, survived flights of up to seven hours in temperatures of 8oC to 25oC in the bay, -42oC to -54oC outside. Dr. Wilson concluded that global movement is unprecedented in volume, reach, and speed and that the distribution of species is changing at unprecedented rates.

(Editor's Note: Other articles commemorating the 75th anniversary of the Harvard School of Public Health have appeared in our Winter and Spring 1997 issues.)

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