Ebola virus from

The first known human cases of Ebola occurred in during two simultaneous outbreaks in Sudan and the Democratic Republic of Congo, which sickened more than people, according to the World Health Organization.

Nearly 20 years later, in , researchers looking for the reservoir of Ebola sampled more than 1, small animals in the Central African nations of Gabon and the Republic of the Congo, which have also experienced outbreaks of Ebola. They tested bats, birds and small terrestrial vertebrates. The only animals found to harbor the Ebola virus were bats, specifically, three species of fruit bat: The hammer-headed bat, Franquet's epauletted fruit bat, and the little collared fruit bat.

At least two of these fruit bat species are also found in Guinea — which is where the current Ebola outbreak in West Africa began — so it's possible that these bats were sources for the outbreak, Gatherer told Live Science. Researchers in Guinea are now sampling bats in that region to see if any test positive for Ebola, Gatherer said. Other contacts of the Liberian patient, including family members who shared an apartment with the patient, did not become infected.

A fourth diagnosis of Ebola infection in the United States occurred later in October when a doctor who had returned to New York from treating patients in Guinea tested positive for Ebola virus.

He was hospitalized and has recovered and is free of the virus. His contacts completed the day follow-up period without becoming infected.

At the end of , the toll of reported cases stood at approximately 20,, of whom more than 7, died. Actual numbers are thought to be higher. Nearly all of the deaths occurred in Liberia, Sierra Leone, and Guinea. There was one death in the United States, six in Mali, and eight in Nigeria. Until December, the highest numbers of cases and deaths had occurred in Liberia, but towards the end of the number of new cases surged in Sierra Leone surpassing the count in Liberia.

Sierra Leone remains the country with the most confirmed cases of EVD, although the death toll is highest in Liberia. Progress became apparent during the early months of when overall numbers of new cases declined. Towards the end of the year, the outbreak was declared over in Liberia in September, in Sierra Leone in November, and in Guinea in December after each of these countries completed a period of 42 days, double the maximum incubation time, in which no new confirmed cases were reported.

By this time, an overall total of more than 28, cases and 11, deaths had occurred as a result of this Ebola virus outbreak. The first outbreak of Ebola virus in the Democratic Republic of the Congo of was reported in early May after two cases caused by the Ebola Zaire virus were confirmed in laboratory tests.

The outbreak was declared ended by the WHO in July after contacts of confirmed cases who had been vaccinated did not display Ebola virus symptoms within 42 days double the maximum incubation period for infection. In total, there were 54 confirmed or probable cases, including 32 deaths, as a result of this outbreak, which was confined to regions within the northwestern part of the country. The four cases in the large urban center of Mbandaka, a major transportation hub, had caused the greatest concern.

The short duration of the first outbreak appeared to be due to benefits from the scientific knowledge gained during the outbreak in West Africa and the results of a vaccination trial conducted in Guinea during Once the outbreak was reported, a wide partnership of governmental and health agencies worked quickly to curtail it.

Using the rVSV-ZEBOV vaccine developed by Merck - which is not yet licensed nor formally approved - but was shown to be safe and effective during the vaccine trial in Guinea, a ring vaccination campaign was undertaken in which the contacts of confirmed cases, and their contacts, as well as healthcare workers and others with potential exposure to the virus were given the experimental vaccine.

More than people were vaccinated. The respite was short-lived, however, as on August 1, a little more than a week later, another outbreak - the tenth in the DRC - was declared.

The new cluster of cases was reported in the North Kivu Province in the northeastern part of the country, a remote, conflict-plagued region that shares porous borders with Uganda and Rwanda and which hosts over a million displaced persons. These conditions have made it much more difficult to curtail the spread of the virus. As of June 1 , a total of EVD cases in two neighboring northeastern provinces North Kivu and Ituri have been reported in this ongoing outbreak according to the World Health Organization.

Of these cases, people have died although the true number of cases and deaths is thought to be higher. This now ranks as the second largest Ebola epidemic ever the outbreak in West Africa was the largest. In spite of the use of proven control measures, such as ring vaccination over , people have been vaccinated so far , and the availability of preventive and therapeutic tools, containment of the virus has been hindered by the geographical challenges, security hazards, distrust of authorities, and a lack of understanding about the disease.

Efforts to control the outbreak were further challenged by attacks on two Ebola treatment centers in late February. The risk of continued national and regional transmission remains very high.

Ebola virus is a class A bioterrorism agent , known to cause highly lethal hemorrhagic fever. The mortality rate can be as high as 90 percent. Because the Ebola virus is so hazardous, it is classified as a biosafety level 4 agent - the level assigned to the most dangerous agents known. Research using Ebola viruses requires facilities with the utmost levels of containment, strict controls on access, and highly trained personnel.

In addition to being classified as a potential bioterrorism agent , the risk of natural outbreaks and the further emergence of Ebola virus is a serious concern.

As the human population grows, human contact with bats or Ebola-infected non-human primates increases, as does human to human spread particularly in the age of air travel. The Ebola virus disease outbreak in West Africa clearly illustrates this risk. The latest outbreak in the Democratic Republic of the Congo, in the latter half of , highlights the complex challenges of curtailing the spread of the virus in regions that are unstable and geographically remote and where there are high levels of misinformation and mistrust of authorities.

There is still no cure for Ebola virus disease and no established drug therapy to treat Ebola infection. There is no approved vaccine that can protect humans against Ebola, although an unlicensed vaccine has been shown to be effective. As is the case for many other viral diseases, such as Zika virus, Ebola was considered a neglected disease because until the total number of infections was low, so there was little investment in anti-viral research.

Scientists lacked sufficient diagnostic tools to rapidly identify Ebola infections. Scientists still need a more thorough understanding about how the virus is transmitted and how it causes disease.

Ebola is a threat not only to humans but also to our closest living relatives - the great apes. Past Ebola infections have wiped out about a third of the gorillas in protected areas, and the western lowland gorilla populations have been decimated by Ebola to such an extent that they are now considered "critically endangered". Facebook Twitter LinkedIn Syndicate. Minus Related Pages. What is Ebola Virus? Prevention and Vaccine. Signs and Symptoms. Outbreak Preparedness. Minus Related Pages.

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