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Plagues--what's past is present: thoughts on the origin and history of new infectious diseases
1Medical Service, Tucson Veterans Affairs Medical Center, Arizona 85723.
Abstract:
Medical science has made tremendous strides in overcoming infectious diseases in the 20th century. Despite this, several epidemics of previously unrecognized diseases have occurred during the last 15 years. These diseases include Lyme disease, Legionnaires' disease, toxic shock syndrome, and AIDS. Examination of past epidemics, including the plague of Athens, the black death, syphilis, and influenza, suggests that the sudden occurrence of diseases that were previously unrecognized is not unusual. Analysis of the new infectious disease indicates that while all four appeared suddenly, isolated cases of the disease occurred before the actual epidemic. Further, all four new diseases were found to be due to agents or toxins that were not previously recognized. Epidemics due to new infectious diseases may arise by several mechanisms, including mutation of the pathogen to a virulent form and introduction of an infectious agent into a nonimmune population. Environmental and behavioral factors may play an important role, as illustrated by toxic shock syndrome, Legionnaires' disease, and AIDS. On the other hand, epidemic diseases tend to abate over time because of changes in the infecting pathogen and in the host. Hence, epidemics can be seen as cycles; new diseases will arise periodically, occasionally with a devastating outcome. With time the effects of these diseases on the population will ameliorate. The cycle will begin again when a new disease emerges.
Insights
New infectious diseases, like Lyme disease and AIDS, emerge periodically, driven by unrecognized agents or toxins. While devastating initially, epidemics naturally abate over time, marking a recurring cycle in disease emergence.
Area of Science:
- Epidemiology
- Infectious Diseases
- Public Health
Background:
- Medical advancements in the 20th century significantly reduced infectious disease impact.
- Recent decades have seen the emergence of novel epidemics, including Lyme disease, Legionnaires' disease, toxic shock syndrome, and Acquired Immunodeficiency Syndrome (AIDS).
- Historical analysis reveals that the emergence of previously unrecognized diseases is a recurring phenomenon throughout history.
Purpose of the Study:
- To analyze the patterns and mechanisms behind the emergence of new infectious diseases.
- To understand the factors contributing to both the rise and eventual decline of epidemics.
- To contextualize recent epidemics within a broader historical and biological framework.
Main Methods:
- Review of historical epidemic data (e.g., plague of Athens, Black Death, syphilis, influenza).
- Analysis of etiological factors and epidemiological characteristics of recent emerging diseases (Lyme disease, Legionnaires' disease, toxic shock syndrome, AIDS).
- Examination of potential contributing factors such as pathogen mutation, host susceptibility, and environmental/behavioral influences.
Main Results:
- Newly identified diseases often have precursor isolated cases before widespread epidemics.
- Emerging infectious diseases are frequently caused by previously unknown agents or toxins.
- Mechanisms for epidemic emergence include pathogen evolution and introduction into naive populations.
- Environmental and behavioral factors significantly influence the spread of diseases like toxic shock syndrome, Legionnaires' disease, and AIDS.
- Epidemics tend to diminish over time due to pathogen and host adaptations.
Conclusions:
- The emergence of new infectious diseases is a cyclical and recurring process in human history.
- Understanding the dynamics of disease emergence and abatement is crucial for public health.
- While new diseases can cause significant mortality, their impact often lessens over time, preceding the emergence of new threats.
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