Maya Pines (ed.), The Race Against Lethal Microbes: Learning to Outwit the Shifty Bacteria, Viruses, and Parasites that Cause Infectious Diseases (Howard Hughes Medical Institute, Chevy Chase, MD, 1996). 56 pp.This is the sixth in a series of reports about biomedical sciences, several of which have been reviewed in previous issues of this Newsletter (p. 24, Winter 1994; p. 19, Spring 1994; p. 34, Spring 1995). Copies may be obtained by contacting the editor at the Howard Hughes Medical Institute, 4000 Jones Bridge Road, Chevy Chase, MD 20815-6789, (301)-215-8500. This new publication in the beautifully illustrated and most informative series follows the usual format of an introductory essay by the editor followed by a series of papers on the topic.
In her introduction Pines contrasts the brouhaha about the terrifying Ebola virus epidemic which took only 244 lives with the relative lack of concern about such ancient scourges as measles, which kills one million people a year and tuberculosis, which kills two million. Infectious diseases are still the leading cause of death worldwide, killing 16.4 million a year. Many which were particularly important in developing countries are now reemerging in the United States and other industrialized countries. One of these, tuberculosis, is closely linked to a newer threat -- AIDS. When AIDS first appeared in the mid-1980s, many thought a vaccine would be developed rapidly. Our failure has exposed our ignorance of the fundamental mechanisms of infection. Other important diseases are mentioned here and discussed in the text, while the centerfold consists of a "Rogue's Gallery" of some of the most important infectious organisms. The poster details how microbes enter our bodies, how they injure us,how we fight them -- and how they fight us! It is sobering to think that we have only eliminated one of hundreds of diseases -- smallpox.
The first article in the publication, "The Return of Tuberculosis in a New, More Menacing Form," by Stephen Hall, details the occurrence in the LaQuinta High School in Southern California of 11 cases of active TB, all contracted from a misdiagnosed case in a student. In all, 178 students and staff tested positive for infection. The article then details characteristics of the disease -- for example, that there are 8 million new cases yearly worldwide and 2 million deaths. Equally detailed is the attempt to conquer the disease, through the development of a more effective vaccine and attempts to develop new more effective drugs to combat the infection. We thought we had them and, for a while, tuberculosis was a treatable disease. Now many strains are turning out to be MDRs -- Multiply Drug Resistant. The overall message is that, in the age of AIDS, tuberculosis has become a quicker, more resilient, more opportunistic killer. The statement in the introduction that infectious diseases are the major causes of death is graphically displayed in a world map on pages 22 and 23.
As already stated, the major killer is tuberculosis with 2 million deaths a year -- from 16,000 in the "established market economies" (i.e., industrialized nations) to 752,000 in India. Sub-Saharan Africa runs a close second with 458,000 deaths. The second killer, believe it or not, is measles. Children must be vaccinated between the time they are nine months of age (when the protection provided by the mother's antibodies has lapsed) and the child's first exposure to the virus -- a narrow window of opportunity. As a result, 206,000 children die of measles in India and as many as 576,000 in Africa.
The third killer is malaria -- and nearly a million children and pregnant women die of this a year. These three are currently the major killers, but AIDS is catching up rapidly. By 2005 the death toll from AIDS is expected to reach 2 million a year, thus rivaling tuberculosis. The combination of tuberculosis and AIDS is a particularly deadly one and is becoming unfortunately common.
The following article, "In Hot Pursuit of a Deadly Parasite," by Deborah Franklin, is mostly devoted to the study of sleeping sickness, a disease caused by a protozoan Trypanosome which has the ability to sprout new coats of antigens (variant surface glycoproteins or VSGs) and defeat the efforts of the immune system to conquer the disease. The complicated workings of this antigenic reaction are detailed in the article. Other parasitic diseases are discussed in separate boxes in the article -- one on a related Trypanosomal disease in Latin America -- Chagas' disease, caused by T. cruzi. The problem detailed here is that surveys seem to indicate that there are now 50,000 to 100,000 people infected with T. cruzi north of the Mexican border (a euphemism for the United States). The threat of our blood banks obtaining blood infected with T. cruzi is an important one -- especially if the blood is used for people with suppressed immune systems. Such people are at risk of developing T. cruzi infections which are rapidly lethal. One patient whose immune system had been weakend by treatment for leukemia has died and the author calls these cases "merely sentinels of many others in whom the infectons are still silent."
A third parasitic infection discussed in the article is malaria, already metioned as a major killer -- and well would it be, with 300 million people suffering from the disease and close to a million deaths a year. The number of cases has doubled in the last ten years. The industrialized nations maintain themselves free of the disease, except for imported cases. Drug therapy, formerly highly successful, is threatened, with many strains of malaria now resistant to antimalarials. Some possible solutions are discussed. The best weapon of all would be an effective vaccine, but this has not been possible to date.
The final article in the booklet is "Can AIDS Be Tamed?" by Maya Pines. It explains that the AIDS virus, HIV, has an enormously high rate of mutation so that by the time treatment is started "a billion to a trillion variants" of HIV may be circulating and inevitably one will prove resistant to the drug. The answer is to hit the virus with three or more drugs at once, and these combinations might serve to keep the virus in check. There have been enough enthusiastic articles and reports in the media to indicate that these multiple-drug approaches work but there is no indication yet that treatment can be stopped after a year or whether this extremely expensive treatment with its vaious side effects would have to go on forever. It does not work in all cases. The problem, of course, is that there are very few antiviral drugs of any kind. Most drugs that would stop viruses would damage human cells as well, since the virus uses the machinery of the host cell to invade.
Pines also discusses the difficulties inherent in the development of a vaccine against AIDS. With a virus as variable as HIV scientists hesitate to use a live virus, so experimental vaccines only contain subunits of HIV. Since 1988 some 13 vaccines of this sort have been investigated. We know that they are safe, but do they actually prevent the disease? Nobody knows.
This is a most valuable publication which will enrich and inform health and biology classes at the senior high level.
- Irma S. Jarcho
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