Disaster movies often portray catastrophes that destroy, or at least threaten to destroy earth's entire population. In fact, a virus emerged in the 1970s that could've been just that fatal. Named after a river that passes through the Congo, the Ebola virus originally manifested itself in the interior of Africa in 1976. Two strains of the disease, with almost identical symptoms, affected humans- Ebola-Zaire and Ebola-Sudan. The Sudan version was deadly enough, killing 50% of those it infected. However, Zaire, with its 90% mortality rate, was even worse. The origins, though not the cause of Ebola-Sudan, can be traced back to a single individual in a Sudanese town. Ebola-Zaire seemed to erupt in over 50 villages simultaneously. Both strains quickly invaded local hospitals when needle sharing and other unhealthy practices ensured the rapid spreading of the infection by bringing people into contact with contaminated body fluids. If the virus had been capable of spreading through the air, or if one infected person had unknowingly entered a large population center, Ebola might have become a worldwide epidemic. However, soon after these fierce outbreaks, the virus died out, at least temporarily. Ebola was so deadly and killed so quickly that within a short period of time, there was no one around to infect. Hospital workers in at least one case deserted their workplace in panic, thus halting the administering of potentially unclean disease spreading injections, but Ebola has not disappeared. With no known vaccination or cure available, it seems only a matter of time until another epidemic erupts.

Questions 22 to 25 are based on the passage you have just heard.

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