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Viruses: At the Threshold of Life |
Chapter: 4
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Emerging Viruses The utter simplicity of a virus may be the key to its ability to mutate, and, with that ability, viruses may easily adapt to human tissues. Virologists have found, for example, that a viral mutation can occur in about one in every 10,000 replications. This rate is magnitudes higher than the rate seen in human cells and much more impressive than the rate for bacteria. Errors in replication occur in RNA viruses, in particular, because they lack the correction mechanisms that DNA viruses possess. Consequently, new and virulent infectious agents may appear regularly in the future—without warning. Viral epidemics have traditionally occurred when human populations have settled into previously inaccessible areas of the globe where viruses were present. Such "virgin" human population centers establish new feeding grounds for the viruses. There is also the possibility that arthropods will carry viruses out of remote areas as global climate patterns shift. Where will these mutations and movements lead? Consider the changes that periodically occur in influenza viruses; or the emergence of Lassa fever, Marburg disease, or Ebola fever; or the AIDS epidemic. It is conceivable that a mutation in a monkey virus led to HIV and that emergence from a remote part of the world followed. As science forges ahead to find cures for known yet poorly understood diseases, it can expect to be continually challenged by the unknown. |
