Frank Ryan, M.D., Virus X: Tracking the New Killer Plagues (Little, Brown, and Co., Boston, 1997). 430 pp. ISBN 0-316-76383-7.
Among the front pages of this new book is a world map with a black dot representing the location of a new virus or strain of disease that has emerged in the last fifty years. Overwhelmingly, these dots originate in tropical and rainforest regions. This book recounts, in detail, the emergence of many of these plagues, some already familiar to our readers from Laurie Garrett's The Coming Plagues, reviewed in our Spring 1995 issue.
Not too long ago we thought we were making progress even against the most refractory infections of all -- viruses -- which disappear into the inner labyrinths of the living cells. Indeed, on 4 December 1967 the Surgeon General of the U.S. Public Health Service informed a meeting of state and territorial health officials that infectious diseases were now conquered. Today, one after the other of the dismissed plagues have returned to haunt us. Tuberculosis, which in a century and a half killed three quarters of a billion people. Malaria, second in line as the greatest killer among the transmissible diseases. Polio, smallpox, measles, many others seemed to be well on the way to extinction. Of all the infectious diseases, only smallpox appears to have been conquered. Today, as one after the other of the dismissed plagues returns to haunt us, new plagues, every bit as deadly as anything seen in previous history, threaten our species. The present generation has thus seen a proliferation of new plagues and a frightening recrudescence of the old ones.
Dr. Ryan gives, in spellbinding detail, the account of the appearance of the Hanta virus. The swift identification of this new plague and the unraveling of its epidemiology is one of the triumphs of modern medical science.
A long and fascinating chapter on the viruses offers a new appreciation (if that's the word I want!) of the importance and ubiquity of this most intriguing of life forms. Some of the characterizations offered in the chapter detail their complexity: viruses are vehicles for genetic exchange between the separate species that make up the matrix of life on earth; they have an exquisite ability to sense the right cell surface. Viruses don't just cause diseases in people; they infect every form of life on earth. They do not grow; they are created in an identical assembly. The majority of viruses do not cause any symptoms of distress or disease. Viruses pose a particular threat because very few are amenable to drug therapy. Viruses have a phenomenal capacity for mutation -- RNA viruses mutate at thousands of times the rate of human cells. There appears to be an inexhaustible supply of new viruses. Quite a scary list!
Another returning plague described by the author is cholera, which had gradually declined during the 1980s. Suddenly, in January 1991, an outbreak was reported in Peru. It spread with unexpected speed and intensity and by March and April was affecting Colombia and Chile. The vibrio has been shown to have the capacity to encyst in a form that could survive for months or even years inside marine algae. It was in this form that the cholera arrived in Peru -- in the ballast tanks of a ship from China that had discharged its ballast in Peruvian coastal waters. The vibrio infected local algae that were food for shellfish, crabs, lobster, and fish and these, in turn, were eaten by people. And thus the epidemic spread. Three years later an estimate of a million cases was regarded as a gross underestimate and there were 10,000 reported deaths from nineteen countries throughout Latin America. The microbe did not confine itself to Latin America -- when the devastation that was the refugee exodus from Rwanda arrived in Zaire cholera broke out and within 24 hours 800 people were dead. From then on it was hard to keep count.
The author offers long and exhaustive accounts of other outbreaks which have become heartbrakingly familiar to us. Plague in India. The explosion of tuberculosis in sub-Saharan Africa and, indeed, worldwide. (Eight million or more people contract this disease each year and 2.9 million die -- the greatest killer among the pathogens.) Outbreaks of malaria, second only to tuberculosis as a killer. (More than a hundred million people worldwide contract the disease each year and approximately one and a half million die from it). The Ebola outbreaks in Africa, again described in great detail. (In one hospital the cause of the spread was easy to find -- all the pregnant women were given injections. Just four or six syringes were issued each day and reused for each patient without sterilization until the end of the day.) Although the Ebola virus could spread by skin contact, injection, and intercourse, it fortunately did not appear to spread by coughing or sneezing. As the author writes, "The world was lucky that year!" There were other epidemics, it would appear, everywhere: the Machupo virus in Bolivia. Lassa fever in eastern Nigeria.
Emerging viruses are characterized by aggressive behavior in a totally novel host yet by seemingly benign behavior in its long-established host. The author ascribes this to co-evolution -- an established theme in the biology of virus-host relationships in which virus and host reach an accommodation, over eons, which can only be characterized as "live and let live." But when a new host intrudes -- man, for example -- all hell breaks loose.
Another exciting chapter details the history of AIDS, familiar to us from numerous books and films. As Dr. Jonathan Mann put it, "The social, cultural, economic, and political reaction to AIDS is as central to the global challenge as AIDS itself." Africa is the tragic epicenter of this epidemic with an estimated 11 to 14 million infections. No less than 190 countries are now reporting AIDS cases. By the turn of the century the World Health Organization estimates that between 30 and 40 million men, women, and children will be infected with HIV-1.
A further chapter details the evidence for the origin of AIDS in Africa. HIV-2, the milder virus, is regarded as simply a strain of a simian virus that had become endemic in West Africa. Both HIV-1 and HIV-2 originated from African rainforest primates. In view of the emergence of Ebola, Marburg, and HIV, it would appear that interference with rainforests and deforestation, in particular, is the most dangerous human activity with regard to epidemic viruses.
Another scary section is devoted to the infections derived from viruses in the oceans such as the 1972 outbreak of paralytic illness in New England associated with a marine red algal tide. In 1978 toxic algae caused an outbreak of fish poisoning in Florida. Today, it is estimated that 200,000 cases of such poisoning occur globally. Indeed, the author states categorically that "Pollution of our seas may well constitute the greatest hidden environmental threat of our age."
What is causing the emergence of these diseases? The author traces them to the increase in human population, which has put an intolerable strain on our resources and led to massive deforestation (whose significance has already been discussed). The speed of travel serves to spread these emerging diseases, in terms of both speed and volume. In 1993 some 500 million passengers were recorded worldwide and, of these, 40 million were traveling between developing and developed countries. All it takes is one.
A final, even more scary, chapter, "Virus X," details the characteristics of a possible new lethal pandemic. It would likely be a virus and, to cause our extinction, would need to take two steps. First, it would have to kill everybody, or nearly everybody it infected. Second, the virus must be able to spread person-to-person by the respiratory route, the only route of contagion universally threatening to humanity. A combination of the infectivity of influenza and the lethality of Ebola or HIV-1. Had HIV-1 spread by aerosol from the beginning, it would have been a true Virus X. Such a virulent pandemic strain would infect up to 50% of the population of the world. The fastest a vacine can be prepared is six months. Perhaps Virus X will be the influenza virus -- a new pandemic is overdue.
As the author wryly concludes, "Anybody who has lived through the past forty years will be familiar with the threat of nuclear annihilation. How curious that as this fear recedes, . . . it has been replaced by a a renewed fear of the threat from mankind's most ancient enemy, disease-causing microbes."
An appendix listing in chronological order all the emerging infections since 1930 with reference notes for each chapter and an extensive index add to the value of the book.
- Irma S. Jarcho
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