DISASTER CAUSED BY BACTERIA
9. Are natural disasters ever caused by micro-
organisms?
Yes. Our world is teaming
with micro-
organisms (one-cell organisms that are too small to see). Most are innocuous, many are beneficial either to plants or animal life, but a few are harmful. The micro-organisms at issue here are bacteria and viruses. The natural disasters that can be caused by bacteria or viruses include such devastating events as the Black Death which killed about one third of the population of Europe in the fourteenth century, and AIDS sometimes seen as the modern Black Death even though its causative factor is different from that of the medieval disease.
10. What micro-organism caused the plague known as the "Black Death"?
The "Black Death" was caused by Yersinia pestis (also called Bacillus pestis and Pasteurella pestis) which is a
bacterium. Yersinia pestis has almost certainly been causing plague epidemics in human populations for more than 2000 years. It was an outbreak of this plague in Europe in the 14th century that was called "The Black Death".
11. When was this plague bacterium identified?
It was identified in 1894 by Alexandre Yersin.
12. What makes this bacterium so dangerous?
The Versinia pestis bacillus (bacterium) is remarkably stable and vigorous. In humans it causes three phases of infection. The bubonic phase involves swelling of the lymph nodes, the pneumonic phase involves the lungs, and in the third, most serious phase called the septicemic phase, the blood stream is invaded and death occurs quickly. The disease can now be controlled and cured with the use of antibiotics.
13. How does a person become infected with this bacterium?
The disease is most commonly passed to humans through bites from fleas that have fed on the domestic rat, Rattus rattus. This was not fully realized until 1914. Today the disease is not common but small outbreaks can still occur in crowded, unsanitary situations where the rat populations are not controlled.