What is the history of Ebola hemorrhagic fever?

Ebola hemorrhagic fever was first noted in Zaire (currently, the Democratic Republic of the Congo or DRC) in 1976. The original outbreak was in a village near the Ebola River after which the disease was named. During that time, the virus was identified in person-to-person contact transmission. Of the 318 patients diagnosed with Ebola, 88% died. Since that time, there have been multiple outbreaks of Ebola virus, and five strains have been identified; four of the strains are responsible for the high death rates. The four Ebola strains are termed as follows: Zaire, Sudan, Tai Forest, and Bundibugyo virus, with Zaire being the most lethal strain. A fifth strain termed Reston has been found in the Philippines.



The strain infects primates, pigs, and humans and causes few if any symptoms and no deaths in humans. Most outbreaks of the more lethal strains of Ebola have occurred in Africa and mainly in small- or medium-sized towns. Bats, monkeys, and other animals are thought to maintain the virus life cycle in the wild; humans can become infected from handling and/or eating infected animals. Once an Ebola outbreak is recognized, African officials isolate the area until the outbreak ceases.

However, in this new outbreak that began in Africa in March 2014, some of the infected patients reached larger city centers before the outbreak was recognized; this caused further spread Ebola. The infecting Ebola virus detected this outbreak is the Zaire strain, the most pathogenic strain of Ebola. Health agencies are terming this outbreak as an "unprecedented epidemic." This epidemic spread quickly in the African countries of Guinea and Sierra Leone. In addition, countries of Liberia, Nigeria, Senegal, and Mali all reported confirmed infections with Ebola.

In addition, a very few sporadic infections were noted in the United States, Spain, and the United Kingdom; most of the individuals with Ebola in these countries were either imported infections from Africa or were new infections from treating patients who originally became infected in Africa.