Here’s a look at Ebola, a virus with a high fatality rate that was first identified in Africa in 1976.
Ebola hemorrhagic fever is a disease caused by one of five different Ebola viruses. Four of the strains can cause severe illness in humans and animals. The fifth, Reston virus, has caused illness in some animals, but not in humans.
The first human outbreaks occurred in 1976, one in northern Zaire (now Democratic Republic of the Congo) in central Africa: and the other, in southern Sudan (now South Sudan). The virus is named after the Ebola River, where the virus was first recognized in 1976, according to the Centers for Disease Control and Prevention (CDC).
Ebola is extremely infectious but not extremely contagious. It is infectious, because an infinitesimally small amount can cause illness. Laboratory experiments on nonhuman primates suggest that even a single virus may be enough to trigger a fatal infection.
Ebola is considered moderately contagious because the virus is not transmitted through the air.
Humans can be infected by other humans if they come in contact with body fluids from an infected person or contaminated objects from infected persons. Humans can also be exposed to the virus, for example, by butchering infected animals.
Symptoms of Ebola typically include: weakness, fever, aches, diarrhea, vomiting and stomach pain. Additional experiences include rash, red eyes, chest pain, throat soreness, difficulty breathing or swallowing and bleeding (including internal).
Typically, symptoms appear eight to 10 days after exposure to the virus, but the incubation period can span two to 21 days.
Ebola is not transmissible if someone is asymptomatic and usually not after someone has recovered from it. However, the virus has been found in the semen of men who have recovered from Ebola and possibly could be transmitted from contact with that semen.
There are five subspecies of the Ebola virus: Zaire ebolavirus (EBOV), Bundibugyo ebolavirus (BDBV), Sudan ebolavirus (SUDV), Taï Forest ebolavirus (TAFV) and Reston ebolavirus (RESTV).
Click here for the CDC’s list of known cases and outbreaks.
2014-2016 West Africa Outbreak
(Full historical timeline at bottom)
March 2014 - The CDC issues its initial announcement on an outbreak in Guinea, and reports of cases in Liberia and Sierra Leone.
April 16, 2014 - The New England Journal of Medicine publishes a report, speculating that the current outbreak’s Patient Zero was a 2-year-old from Guinea. The child died on December 6, 2013, followed by his mother, sister and grandmother over the next month.
August 8, 2014 - Experts at the World Health Organization (WHO) declare the Ebola epidemic ravaging West Africa an international health emergency that requires a coordinated global approach, describing it as the worst outbreak in the four-decade history of tracking the disease.
August 19, 2014 - Liberia’s President Ellen Johnson Sirleaf declares a nationwide curfew beginning August 20 and orders two communities to be completely quarantined, with no movement into or out of the areas.
September 16, 2014 - US President Barack Obama calls the efforts to combat the Ebola outbreak centered in West Africa “the largest international response in the history of the CDC.” Speaking from the CDC headquarters in Atlanta, Obama adds that “faced with this outbreak, the world is looking to” the United States to lead international efforts to combat the virus.
October 6, 2014 - A nurse’s assistant in Spain becomes the first person known to have contracted Ebola outside Africa in the current outbreak. The woman helped treat two Spanish missionaries, both of whom had contracted Ebola in West Africa, one in Liberia and the other in Sierra Leone. Both died after returning to Spain. On October 19, Spain’s Special Ebola Committee says that nurse’s aide Teresa Romero Ramos is considered free of the Ebola virus.
October 8, 2014 - Thomas Eric Duncan, a Liberian citizen who was visiting the United States, dies of Ebola in Dallas.
October 11, 2014 - Nina Pham, a Dallas nurse who cared for Duncan, tests positive for Ebola during a preliminary blood test. She is the first person to contract Ebola on American soil.
October 15, 2014 - Amber Vinson, a second Dallas nurse who cared for Duncan, is diagnosed with Ebola. Authorities say Vinson flew on a commercial jet from Cleveland to Dallas days before testing positive for Ebola.
October 20, 2014 - Under fire in the wake of Ebola cases involving two Dallas nurses, the CDC issues updated Ebola guidelines that stress the importance of more training and supervision, and recommend that no skin be exposed when workers are wearing personal protective equipment, or PPE.