The ongoing 2014 West African Ebola outbreak has terrorized the region with its high death rate, made worse by the lack of a specific treatment for the virus.

Human history is rife with examples of attacks by deadly viruses. Some of them featured high death rates that turned prosperous cities into ghost towns. Others recurred several times, leaving the specter of fear in people's hearts. Although some of these viruses have been eliminated or controlled, many of them still don't have effective treatments.

　　Yellow fever

　　Yellow fever [baike.sogou.com]

Yellow fever is an acute viral disease first found in South America and Sub-Saharan Africa. It is spread by the bite of the female mosquito. Patients exhibit symptoms including fever, chills, muscle pains (particularly in the back) and headaches within three to five days after infection. According to historical records, 300,000 people died of the disease in the 19th century.