A nurse who had contact with this patient during his second hospital stay was confirmed to have EVD on Oct. This was the first known case of transmission within the United States. A second nurse at the same hospital tested positive for Ebola three days later.
Both nurses recovered and have been declared free of the virus. 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".
The Ebola outbreak was unprecedented for several reasons. First, it occurred in a region of Africa in which Ebola had never before been detected. This made it difficult for healthcare workers to swiftly identify Ebola as the cause of infection, whose early symptoms are similar to other diseases in the region. Second, unlike previous episodes which were confined largely to remote areas, this outbreak began near the borders of three countries - Guinea, Liberia, and Sierra Leone - where there is a lot of travel, and it spread rapidly not only to rural regions as in previous outbreaks, but also to densely populated areas.
This resulted in an outbreak that involved multiple regions in the three hardest hit countries. Additionally, it was the first time that Ebola was carried by air travel from one country to another.
Further, the outbreak occurred in countries with weak healthcare infrastructure and a population that is distrustful of government and healthcare workers.
Because it encompassed a much wider geographic area and denser population areas than previous outbreaks, containment was vastly more difficult and complex. It was an immense challenge to control the outbreak in this impoverished part of the world, lacking many basic and essential medical supplies.
Workers faced the daunting task of identifying and quarantining large numbers of infected individuals and their contacts and providing medical care to patients - without sufficient numbers of health workers, personal protective equipment, adequate facilities, or sufficient numbers of hospital beds. Many infected individuals initially were turned away from health facilities and sent home, where they were more likely to infect others, due to lack of space in hospitals.
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The second outbreak occurred in what is now South Sudan, approximately miles km away. Since then, six different species of ebolavirus have been discovered, four of which are known to cause disease in people. Filoviruses are zoonotic, meaning they are transmitted from animals to people.
The reservoir host of Marburg virus is the African fruit bat, but further study is needed to determine if other species may also serve as hosts. Scientists have not determined the host for Ebola virus, although bats are likely involved and may be the reservoir.
Factors like population growth, encroachment into forested areas, and direct interaction with wildlife such as bushmeat consumption may contribute to the introduction of filoviruses into human populations. Those at highest risk of infection are caretakers and healthcare providers who do not use appropriate personal protective equipment PPE.
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