Ebola

Ebola virus disease (EVD)

, Ebola hemorrhagic fever (EHF) or simply Ebola is a disease of humans and other mammals caused by an ebolavirus. Signs and symptoms typically start between 2 days and 3 weeks after contracting the virus, with a fever, sore throat, muscle pain and headaches. Then, vomiting, diarrhea and rash usually follows, along with decreased function of the liver and kidneys. Around this time, infected people may begin to bleed both within the body and externally. Death, if it occurs, is typically 6 to 16 days from the start of symptoms and is often due to low blood pressure from fluid loss.
The virus may be acquired upon contact with blood or other body fluids of an infected human or other animal. Spread through the air has not been documented in the natural environment. Fruit bats are believed to be the normal carrier in nature, able to spread the virus without being affected. Humans become infected by contact with the bats or a living or dead animal that have been infected by bats. Once human infection occurs, the disease may spread between people as well. Male survivors may be able to transmit the disease via semen for nearly two months. To diagnose EVD, other diseases with similar symptoms such as malaria, cholera and other viral hemorrhagic fevers are first excluded. Blood samples are tested for viral antibodies, viral RNA, or the virus itself to confirm the diagnosis.
Outbreak control requires a coordinated series of medical services, along with a certain level of community engagement. The necessary medical services include rapid detection and contact tracing, quick access to appropriate laboratory services, proper management of those who are infected, and proper disposal of the dead through cremation or burial. Prevention includes decreasing the spread of disease from infected animals to humans. This may be done by only handling potentially infected bush meat while wearing proper protective clothing and by thoroughly cooking it before consumption. It also includes wearing proper protective clothing and washing hands when around a person with the disease. Samples of body fluids and tissues from people with the disease should be handled with special caution.
No specific treatment for the disease is yet available. Efforts to help those who are infected are supportive and include giving either oral rehydration therapy (slightly sweet and salty water to drink) or intravenous fluids. This supportive care improves outcomes. The disease has a high risk of death, killing between 25% and 90% of those infected with the virus (average is 50%). EVD was first identified in an area of Sudan (now part of South Sudan), as well as in Zaire (now the Democratic Republic of the Congo). The disease typically occurs in outbreaks in tropical regions of sub-Saharan Africa. From 1976 (when it was first identified) through 2013, the World Health Organization reported a total of 1,716 cases. The largest outbreak to date is the ongoing 2014 West African Ebola outbreak, which is currently affecting Guinea, Sierra Leone, and Liberia. As of 15 October 2014, 8,998 suspected cases resulting in the deaths of 4,493 have been reported.[8][9] Efforts are under way to develop a vaccine; however, none yet exists.

Signs and symptoms

The time between exposure to the virus and the development of symptoms of the disease is usually 2 to 21 days. Some have estimated that around 5% of cases may take greater than 21 days to develop.
Symptoms usually begin with a sudden influenza-like stage characterized by feeling tired, fever, and pain in the muscles and joints. The fever is usually greater than 38.3 °C (100.9 °F). This is than often followed by vomiting, diarrhea and abdominal pain. Shortness of breath and chest pain may occur next along with swelling, headaches and confusion. In about half of cases, the skin may develop a maculopapular rash (a flat red area covered with small bumps).
The bleeding phase typically begins five to seven days after first symptoms. All people show some decreased blood clotting. Bleeding from mucous mebranes or from sites of needle punctures is reported in 40–50% of cases.[16] This may result in the vomiting of blood, coughing up of blood or blood in stool. Bleeding into the skin may create petechiae, purpura, ecchymoses, hematomas (especially around needle injection sites). There may alos be bleeding into the whites of the eyes. Heavy bleeding is uncommon and is usually confined to the gastrointestinal tract.
Recovery may begin between 7 and 14 days after the start of symptoms. While, death, if it occurs, is typically 6 to 16 days from the start of symptoms and is often due to low blood pressure from fluid loss. In general, the development of bleeding often indicates a worse outcome and this blood loss can result in death. People are often in a coma near the end of life. Those who survive often have ongoing muscle and joint pain, liver inflammation, and decreased hearing among other difficulties.

Cause

Ebolavirus (taxonomic group) and Ebola virus (specific virus) Ebola virus disease in humans is caused by four of five viruses in the genus Ebolavirus. The four are Bundibugyo virus (BDBV), Sudan virus (SUDV), Taï Forest virus (TAFV), and one called, simply, Ebola virus (EBOV, formerly Zaire Ebola virus). Ebola virus is the only member of the Zaire ebolavirus species and the most dangerous of the known EVD-causing viruses, as well as being responsible for the largest number of outbreaks. The fifth virus, Reston virus (RESTV), is not thought to cause disease in humans, but has caused disease in non-human primates. These five viruses are closely related to marburgviruses.

Transmission

The spread of Ebola between people occurs only by direct contact with the blood or body fluids of a person after symptoms have developed.[1] This includes embalming of an infected dead body or by contact with objects contaminated by the virus, particularly needles and syringes.[23][24] Body fluids that may transmit ebolaviruses include saliva, mucus, vomit, feces, sweat, tears, breast milk, urine, and semen. Entry points include the nose, mouth, eyes, or open wounds, cuts and abrasions. Transmission from other animals to humans occurs only via contact with body fluids of, or consumption of, an infected mammal, such as a fruit bat, or ape. This is also believed to be the method that has led to human outbreaks.[26][27] The potential for widespread EVD infections in countries with medical systems capable of observing the correct medical isolation procedures is considered low. An infected individual with mild early stage symptoms may feel well enough to travel without assistance. At that stage however, that person's ability to spread the disease is often limited.[citation needed] As transmission via air is generally ruled out, the possibility of transmission between non-seat-mate airline passengers is unlikely.[28] Because dead bodies are still infectious, traditional burial rituals may spread the disease. Nearly two thirds of the cases of Ebola infections in Guinea during the 2014 outbreak are believed to have been contracted via unprotected (or unsuitably protected) contact with infected corpses during certain Guinean burial rituals.[29][30] EBOV and SUDV may be able to persist in the semen of survivors for up to seven weeks, which could give rise to infections and disease via sexual intercourse.[1] It is not entirely clear how an outbreak is initially started.
One of the primary reasons for spread is that the health systems function poorly in parts of Africa where the disease mostly occurs.[32] Medical workers who do not wear appropriate protective clothing may contract the disease.[33] Hospital-acquired transmission has occurred in the United States and African countries due to the reuse of needles or lack of body substance isolation. Some healthcare centers caring for people with the disease do not have running water.
Airborne transmission has not been documented during EVD outbreaks. Transmission among rhesus monkeys via breathable 0.8–1.2 μm airborne droplets has been demonstrated in the laboratory.

Reservoir

Bushmeat being prepared for cooking in Ghana, 2013. Human consumption of equatorial animals in Africa in the form of bushmeat has been linked to the transmission of diseases to people, including Ebola. Bats are considered the most likely natural reservoir of EBOV. Plants, arthropods, and birds have also been considered.[1][41] In the wild, transmission may occur when infected fruit bats drop partially eaten fruits or fruit pulp, then land mammals such as gorillas and duikers may feed on these fallen fruits. This chain of events forms a possible indirect means of transmission from the natural host species to other animal species, which has led to research into viral shedding in the saliva of fruit bats. Fruit production, animal behavior, and other factors vary at different times and places that may trigger outbreaks among animal populations.
Bats were known to reside in the cotton factory in which the first cases of the 1976 and 1979 outbreaks were observed, and they have also been implicated in Marburg virus infections in 1975 and 1980. Of 24 plant species and 19 vertebrate species experimentally inoculated with EBOV, only bats became infected. The bats displayed no clinical signs and is evidence that these bats are a reservoir species of the virus. In a 2002–2003 survey of 1,030 animals including 679 bats from Gabon and the Republic of the Congo, 13 fruit bats were found to contain EBOV RNA fragments. As of 2005, three types of fruit bats (Hypsignathus monstrosus, Epomops franqueti, and Myonycteris torquata) have been identified as being in contact with EBOV. They are now suspected to represent the EBOV reservoir hosts. Antibodies against Zaire and Reston viruses have been found in fruit bats in Bangladesh, thus identifying potential virus hosts and signs of the filoviruses in Asia. Between 1976 and 1998, in 30,000 mammals, birds, reptiles, amphibians and arthropods sampled from outbreak regions, no Ebola virus was detected apart from some genetic traces found in six rodents (Mus setulosus and Praomys) and one shrew (Sylvisorex ollula) collected from the Central African Republic.[43][48] Traces of EBOV were detected in the carcasses of gorillas and chimpanzees during outbreaks in 2001 and 2003, which later became the source of human infections. However, the high lethality from infection in these species makes them unlikely as a natural reservoir.

Virology

Ebolavirus (taxonomic group) and Ebola virus (specific virus) They contain single-strand, non-infectious RNA genomes.[49] Ebolavirus genomes are approximately 19 kilobase pairs long and contain seven genes in the order 3'-UTR-NP-VP35-VP40-GP-VP30-VP24-L-5'-UTR.[50] The genomes of the five different ebolaviruses (BDBV, EBOV, RESTV, SUDV, and TAFV) differ in sequence and the number and location of gene overlaps. Like all filoviruses, ebolavirions are filamentous particles that may appear in the shape of a shepherd's crook or in the shape of a "U" or a "6", and they may be coiled, toroid, or branched.[50] In general, ebolavirions are 80 nm in width, but vary somewhat in length. In general, the median particle length of ebolaviruses ranges from 974 to 1,086 nm (in contrast to marburgvirions, whose median particle length was measured at 795–828 nm), but particles as long as 14,000 nm have been detected in tissue culture. Their life cycle begins with virion attachment to specific cell-surface receptors, followed by fusion of the virion envelope with cellular membranes and the concomitant release of the virus nucleocapsid into the cytosol. Ebolavirus' structural glycoprotein (known as GP1,2) is responsible for the virus' ability to bind to and infect targeted cells.[52] The viral RNA polymerase, encoded by the L gene, partially uncoats the nucleocapsid and transcribes the genes into positive-strand mRNAs, which are then translated into structural and nonstructural proteins. The most abundant protein produced is the nucleoprotein, whose concentration in the cell determines when L switches from gene transcription to genome replication. Replication results in full-length, positive-strand antigenomes that are, in turn, transcribed into negative-strand virus progeny genome copy. Newly synthesized structural proteins and genomes self-assemble and accumulate near the inside of the cell membrane. Virions bud off from the cell, gaining their envelopes from the cellular membrane they bud from. The mature progeny particles then infect other cells to repeat the cycle. The Ebola virus genetics are difficult to study due to its virulent nature.[53]

Pathophysiology

Cells lining the inside of blood vessels (endothelial cells), macrophages, monocytes, and liver cells are the main targets of infection. After infection, a secreted glycoprotein, known as small soluble glycoprotein (sGP) or as the Ebola virus glycoprotein (GP), is synthesized. Ebolavirus replication overwhelms protein synthesis of infected cells and host immune defenses. The GP forms a trimeric complex, which binds the virus to the endothelial cells. The sGP forms a dimeric protein that interferes with the signaling of neutrophils, a type of white blood cell, which allows the virus to evade the immune system by inhibiting early steps of neutrophil activation. These white blood cells also serve as carriers to transport the virus throughout the entire body to places such as the lymph nodes, liver, lungs, and spleen.[54] The presence of viral particles and cell damage resulting from budding causes the release of chemical signals (TNF-α, IL-6, IL-8, etc.), which are molecular signals for fever and inflammation. The damage to human cells, caused by infection of the endothelial cells, decreases blood vessel integrity. This loss of vascular integrity is furthered with the synthesis of GP, which reduces specific integrins responsible for cell adhesion to the intercellular structure, and damage to the liver, which leads to improper clotting.[55] Filoviral infection is also known to interfere with proper functioning of the innate immune system.[56] Ebolavirus proteins have demonstrated the ability to blunt the human immune system's response to viral infections by interfering with cells' ability to produce and respond to interferon proteins such as interferon-alpha, interferon-beta, and interferon gamma.[52][57] This interference is accomplished by the VP24 and VP35 ebolavirus structural proteins. When cells are infected with ebolavirus, receptors located in the cell's cytosol (such as RIG-I and MDA5) or outside of the cytosol (such as Toll-like receptor 3, Toll-like receptor 7, Toll-like receptor 8, and Toll-like receptor 9), recognize infectious molecules associated with the virus.[52] After these receptors are activated, proteins including interferon regulatory factor 3 and interferon regulatory factor 7 start a signaling cascade that leads to the expression of type 1 interferons.[52] Type 1 interferons are then released and bind to neighboring uninfected cells expressing the IFNAR1 and IFNAR2 receptors on their surface.[52] Once interferon has bound to its receptors on the neighboring uninfected cell, the signaling proteins STAT1 and STAT2 are activated and move to the uninfected cell's nucleus.[52] This triggers the expression of interferon-stimulated genes, which code for proteins that have antiviral properties.[52] Ebolavirus' V24 protein prevents the STAT1 signaling protein in the neighboring uninfected cells from entering the cell's nucleus and therefore prevents the creation of these antiviral proteins.[52] A separate ebolavirus protein, known as VP35, directly inhibits the production of interferon-beta.

Diagnosis

The travel and work history along with exposure to wildlife are important to consider when the diagnosis of EVD is suspected. The diagnosis is confirmed by isolating the virus, detecting its RNA or proteins, or detecting antibodies against the virus in a person's blood. Isolating the virus by cell culture, detecting the viral RNA by polymerase chain reaction (PCR) and detecting proteins by enzyme-linked immunosorbent assay (ELISA) works best early and in those who have died from the disease. Detecting antibodies against the virus works best late in the disease and in those who recover.[58] During an outbreak, virus isolation is often not feasible. The most common diagnostic methods are therefore real-time PCR and ELISA detection of proteins, which can be performed in field or mobile hospitals.[59] Filovirions can be seen and identified in cell culture by electron microscopy due to their unique filamentous shapes, but electron microscopy cannot tell the difference between the various filoviruses despite there being some length differences.

Laboratory testing

Changes on laboratory tests as a result of Ebola virus disease include a low platelet count in the blood, an initially decreased white blood cell count followed by an increase in the white blood cell count, elevated levels of the liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and abnormalities in clotting often consistent with disseminated intravascular coagulation (DIC) such as a prolonged prothrombin time, partial thromboplastin time, and bleeding time.[60]

Differential diagnosis

Early symptoms of EVD may be similar to those of other diseases common in Africa including malaria and dengue fever .[12] The symptoms are also similar to those of Marburg virus disease and other viral hemorrhagic fevers.[61] The complete differential diagnosis is long and includes many other infectious diseases such as typhoid fever, shigellosis, rickettsial diseases, cholera, sepsis, borreliosis, EHEC enteritis, leptospirosis, scrub typhus, plague, Q fever, candidiasis, histoplasmosis, trypanosomiasis, visceral leishmaniasis, measles, and viral hepatitis among others.[62] Non-infectious diseases that can be confused with EVD include acute promyelocytic leukemia, hemolytic uremic syndrome, snake envenomation, clotting factor deficiencies/platelet disorders, thrombotic thrombocytopenic purpura, hereditary hemorrhagic telangiectasia, Kawasaki disease, and warfarin poisoning among others.

Prevention

Infection control

The risk of transmission is increased amongst Ebola caregivers. Recommended measures when caring for people infected with Ebola include barrier-isolation, sterilizing equipment and surfaces, and wearing protective clothing including masks, gloves, gowns, and goggles.[31] If a person with Ebola dies, direct contact with the body of the deceased patient should be avoided.[31] The care of those individuals who have become infected with Ebola must be administered while carefully observing a very high-level of barrier-separation from the person infected, along with various certain cleaning and disinfection techniques.[67] Education of those who provide care in these techniques, and the provision of such barrier-separation supplies has been a priority of the Doctors Without Borders organization.[68] Successfully addressing one of the "biggest danger(s) of infection" faced by medical staff requires learning proper suit-up and removal of personal protective equipment. In Sierra Leone, the typical training period for the use of such safety equipment lasts approximately 12 days.[69] One step recommended by the World Health Organization is the education of the general public of the risk factors for Ebola infection and of the protective measures individuals can take.[1] These include avoiding direct contact with infected people and regular hand washing using soap and water.[70] Bushmeat, an important source of protein in the diet of some Africans, should be handled with appropriate protective clothing and thoroughly cooked before consumption.[1] Some research suggests that an outbreak in the wild animals used for consumption may result in a corresponding human outbreak. Since 2003, such animal outbreaks have been monitored with the aim of predicting and preventing Ebola outbreaks in humans.[71] Older burial rituals, which might have included making any kind of direct contact with a corpse, require reformulation such that they consistently maintain a proper protective barrier between the corpse and the living.[72][73] Risk of transmission does not end with a person's death, and thus it is recommended that the bodies of people who have died from Ebola be buried or cremated only with proper care.[74] Social anthropologists may help find alternatives to traditional rules for burials.[75] Airline crews are instructed to follow a certain isolation procedure should anyone exhibit symptoms resembling the Ebola virus disease.[76] Ebolaviruses can be eliminated with heat (heating for 30 to 60 minutes at 60 °C or boiling for 5 minutes). To disinfect surfaces, some lipid solvents such as some alcohol-based products, detergents, sodium hypochlorite (bleach) or calcium hypochlorite (bleaching powder), and other suitable disinfectants at appropriate concentrations can be used. as disinfectants.[77][78] In laboratories where diagnostic testing is carried out, biosafety level 4-equivalent containment is required, since ebolaviruses are World Health Organization Risk Group 4 pathogens. Laboratory researchers must be properly trained in BSL-4 practices and wear proper personal protective equipment.

Quarantine

Quarantine, also known as enforced isolation, is usually effective in decreasing spread.[79][80] Governments often quarantine areas where the disease is occurring or individuals who may transmit the disease outside of an initial area. In the United States, the law allows quarantine of those infected with ebolaviruses. During the 2014 outbreak, Liberia closed schools. On October 16, 2014, some schools were closed in Ohio and Texas as a precaution after one of two nurses who contracted Ebola after caring for Dallas Ebola victim Thomas Eric Duncan, had returned to the Cleveland area and may have been on the same plane as some students, teachers and parents of students from those schools.

Contact tracing

Contact tracing is regarded as important to contain an outbreak. It involves finding everyone who had close contact with infected individuals and watching for signs of illness for 21 days. If any of these contacts comes down with the disease, they should be isolated, tested, and treated. Then repeat the process by tracing the contacts' contacts.

Treatment

Standard support

No ebolavirus-specific treatment is currently approved. However, survival is improved by early supportive care with rehydration and symptomatic treatment. Treatment is primarily supportive in nature. These measures may include management of pain, nausea, fever and anxiety, as well as rehydration via the oral or by intravenous route. Blood products such as packed red blood cells, platelets or fresh frozen plasma may also be used. Other regulators of coagulation have also been tried including heparin in an effort to prevent disseminated intravascular coagulation and clotting factors to decrease bleeding. Antimalarial medications and antibiotics are often used before the diagnosis is confirmed, though there is no evidence to suggest such treatment is in any way helpful.

Intensive care

Intensive care is often used in the developed world. This may include maintaining blood volume and electrolytes (salts) balance as well as treating any bacterial infections that may develop. Dialysis may be needed for kidney failure while extracorporeal membrane oxygenation may be used for lung dysfunction.

Alternative medicine

The Food and Drug Administration (FDA) advises people to be careful of advertisements making unverified or fraudulent claims of benefits supposedly gained from various anti-Ebola products. The FDA has already sent out at least one letter of warning to a seller of colloidal silver who made unverified claims of Ebola related benefits, supposedly derived from the use of their products.

Prognosis

Ebola virus disease has a high risk of death in those infected which varies between 25 percent and 90 percent of those infected. As of September 2014, the average risk of death among those infected is 50%. The risk of death was 90% in the 2002–2003 Republic of the Congo outbreak. There are indications based on variations between countries that early and effective treatment of symptoms (e.g., supportive care to prevent dehydration) may reduce the risk of death. If an infected person survives, recovery may be quick and complete. Prolonged cases are often complicated by the occurrence of long-term problems, such as inflammation of the testicles, joint pains, muscle pains, skin peeling, or hair loss. Eye symptoms, such as light sensitivity, excess tearing, iritis, iridocyclitis, choroiditis, and blindness have also been described.

Epidemiology

The disease typically occurs in outbreaks in tropical regions of Sub-Saharan Africa. From 1976 (when it was first identified) through 2013, the World Health Organization reported 1,716 confirmed cases. The largest outbreak to date is the ongoing 2014 West Africa Ebola virus outbreak, which is affecting Guinea, Sierra Leone, Liberia and Nigeria. As of 15 October, 8,997 suspected cases have been identified, with 4,496 deaths.

1976

The first known outbreak of Ebola virus disease (EVD) was identified only after the fact, occurring between June and November 1976 in Nzara, South Sudan, (then part of Sudan) and was caused by Sudan virus (SUDV). The Sudan outbreak infected 284 people and killed 151. The first identifiable case in Sudan occurred on 27 June in a storekeeper in a cotton factory in Nzara, who was hospitalized on 30 June and died on 6 July. While the WHO medical staff involved in the Sudan outbreak were aware that they were dealing with a heretofore unknown disease, the actual "positive identification" process and the naming of the virus did not occur until some months later in the Democratic Republic of the Congo. On 26 August 1976, a second outbreak of EVD began in Yambuku, a small rural village in Mongala District in northern Democratic Republic of the Congo (then known as Zaire). This outbreak was caused by Ebola virus (EBOV), formerly designated Zaire ebolavirus, which is a different member of the genus Ebolavirus than in the first Sudan outbreak. The first person infected with the disease was village school headmaster Mabalo Lokela, who had toured an area near the Central African Republic border along the Ebola River between 12–22 August. He died on 8 September from the disease. Soon after his death, others who had been in contact with him also died, and people in the village of Yambuku began to panic. This led the country's Minister of Health along with Zaire President Mobutu Sese Seko to declare the entire region, including Yambuku and the country's capital, Kinshasa, a quarantine zone. No one was permitted to enter or leave the area, with roads, waterways, and airfields placed under martial law. Schools, businesses and social organizations were closed. Researchers from the CDC, including Peter Piot, co-discoverer of Ebola, later arrived to assess the effects of the outbreak, observing that "the whole region was in panic." The outbreak lasted 26 days, with the quarantine lasting two weeks. Among the reasons that researchers speculated caused the disease to disappear, were the precautions taken by locals, the quarantine of the area, and possibly most important, the discontinuance of reusing needles by local nurses. The virus responsible for the initial outbreak, first thought to be Marburg virus, was later identified as a new type of virus related to marburgviruses. Virus strain samples isolated from both outbreaks were named as the "Ebola virus" after the Ebola River, located near the originally identified viral outbreak site in Zaire. Reports conflict about who initially coined the name: either Karl Johnson of the American CDC team or Belgian researchers. Subsequently a number of other cases were reported, almost all centered on the Yambuku mission hospital or having close contact with another case. 318 cases and 280 deaths (a 88% fatality rate) occurred in the DRC. Although it was assumed that the two outbreaks were connected, scientists later realized that they were caused by two distinct ebolaviruses, SUDV and EBOV. The Zaire outbreak was contained with the help of the World Health Organization and transport from the Congolese air force, by quarantining villagers, sterilizing medical equipment, and providing protective clothing.

1995 to 2013

The second major outbreak occurred in 1995 in the Democratic Republic of Congo, affecting 315 and killing 254. The next major outbreak occurred in Uganda in 2000, affecting 425 and killing 224; in this case the Sudan virus was found to be the ebolavirus species responsible for the outbreak. In 2003 there was an outbreak in the Republic of Congo that affected 143 and killed 128, a death rate of 90%, the highest to date. In 2004 a Russian scientist died from Ebola after sticking herself with an infected needle. In August 2007, 103 people were infected by a suspected hemorrhagic fever outbreak in the village of Kampungu, Democratic Republic of the Congo. The outbreak started after the funerals of two village chiefs, and 217 people in four villages fell ill. The 2007 outbreak eventually affected 264 individuals and resulted in the deaths of 187. On 30 November 2007, the Uganda Ministry of Health confirmed an outbreak of Ebola in the Bundibugyo District in Western Uganda. After confirmation of samples tested by the United States National Reference Laboratories and the Centers for Disease Control, the World Health Organization confirmed the presence of a new species of Ebolavirus, which was tentatively named Bundibugyo. The WHO reported 149 cases of this new strain and 37 of those led to deaths. The WHO confirmed two small outbreaks in Uganda in 2012. The first outbreak affected 7 people and resulted in the death of 4 and the second affected 24, resulting in the death of 17. The Sudan variant was responsible for both outbreaks. On 17 August 2012, the Ministry of Health of the Democratic Republic of the Congo reported an outbreak of the Ebola-Bundibugyo variant in the eastern region. Other than its discovery in 2007, this was the only time that this variant has been identified as the ebolavirus responsible for an outbreak. The WHO revealed that the virus had sickened 57 people and claimed 29 lives. The probable cause of the outbreak was tainted bush meat hunted by local villagers around the towns of Isiro and Viadana.

2014 West African outbreak

In March 2014, the World Health Organization (WHO) reported a major Ebola outbreak in Guinea, a western African nation. Researchers traced the outbreak to a two-year old child who died on 28 December 2013. The disease then rapidly spread to the neighboring countries of Liberia and Sierra Leone. It is the largest Ebola outbreak ever documented, and the first recorded in the region. On 8 August 2014, the WHO declared the epidemic to be an international public health emergency. Urging the world to offer aid to the affected regions, the Director-General said, "Countries affected to date simply do not have the capacity to manage an outbreak of this size and complexity on their own. I urge the international community to provide this support on the most urgent basis possible." By mid-August 2014, Doctors Without Borders reported the situation in Liberia's capital Monrovia as "catastrophic" and "deteriorating daily". They reported that fears of Ebola among staff members and patients had shut down much of the city’s health system, leaving many people without treatment for other conditions. By late August 2014, the disease had spread to Nigeria, and one case was reported in Senegal. On 30 September 2014, the first confirmed case of Ebola in the United States was diagnosed. The patient died eight days later. Aside from the human cost, the outbreak has severely eroded the economies of the affected countries. A Financial Times report suggested the economic impact of the outbreak could kill more people than the virus itself. As of 23 September, in the three hardest hit countries, Liberia, Sierra Leone, and Guinea, there were only 893 treatment beds available while the current need was 2122. In a 26 September statement, the WHO said, "The Ebola epidemic ravaging parts of West Africa is the most severe acute public health emergency seen in modern times. Never before in recorded history has a biosafety level four pathogen infected so many people so quickly, over such a broad geographical area, for so long." As of 15 October 2014, 8,998 suspected cases and 4,493 deaths had been reported; however, the World Health Organization has said that these numbers may be vastly underestimated. The WHO reports that more than 216 healthcare workers are among the dead, partly due to the lack of equipment and long hours.

2014 international spread

As of 15 October, 2014, there have been 17 cases of Ebola treated outside of Africa, four of whom have died. In early October, Teresa Romero, a 44-year-old Spanish nurse, contracted Ebola after caring for a priest who had been repatriated from west Africa. This was the first transmission of the virus to occur outside of Africa. On 19 September, Eric Duncan flew from his native Liberia to Texas; five days later he began showing symptoms and visited a hospital, but was sent home. His condition worsened and he returned to the hospital on 28 September. Health officials confirmed a diagnosis of Ebola on 30 September—the first case in the United States. On 12 October, the CDC confirmed that a nurse in Texas who had treated Duncan was found to be positive for the Ebola virus, the first known case of the disease to be contracted in the United States. On 15 October a second Texas healthcare worker was confirmed to have the virus.

Society and culture

Ebolavirus is classified as a biosafety level 4 agent, as well as a Category A bioterrorism agent by the Centers for Disease Control and Prevention. It has the potential to be weaponized for use in biological warfare, and was investigated by the Biopreparat for such use, but might be difficult to prepare as a weapon of mass destruction because the virus becomes ineffective quickly in open air.

Other animals

Wild animals

Ebola has a high mortality among primates. Frequent outbreaks of Ebola may have resulted in the deaths of 5,000 gorillas. Outbreaks of Ebola may have been responsible for an 88% decline in tracking indices of observed chimpanzee populations in 420 square kilometer Lossi Sanctuary between 2002 and 2003. Transmission among chimpanzees through meat consumption constitutes a significant risk factor, while contact between the animals, such as touching dead bodies and grooming, is not. Recovered carcasses from gorillas contain multiple Ebola virus strains, which suggest multiple introductions of the virus. Bodies decompose quickly and carcasses are not infectious after three to four days. Contact between gorilla groups is rare, suggesting transmission among gorilla groups is unlikely, and that outbreaks result from transmission between viral reservoir and animal populations.

Domesticated animals

In late 1989, Hazelton Research Products' Reston Quarantine Unit in Reston, Virginia, suffered a mysterious outbreak of fatal illness amongst certain lab monkeys. This lab outbreak was initially diagnosed as Simian hemorrhagic fever virus (SHFV), and occured amongst a shipment of crab-eating macaque monkeys imported from the Philippines. Hazelton's veterinary pathologist sent tissue samples from dead animals to the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) at Fort Detrick, Maryland, where an ELISA test indicated the antibodies present in the tissue were a response to ebola virus and not SHFV. An electron microscopist from USAMRIID discovered filoviruses similar in appearance to Ebola in the tissue samples sent from Hazelton Research Products' Reston Quarantine Unit. Shortly afterward, a US Army team headquartered at USAMRIID went into action to euthanize the monkeys which had not yet died, bringing those monkeys and those which had already died of the disease to Ft. Detrick for study by the Army's veterinary pathologists and virologists, and eventual disposal under safe conditions. Blood samples were taken from 178 animal handlers during the incident. Of those, six animal handlers eventually seroconverted, including one who had cut himself with a bloody scalpel. Despite its status as a Level‑4 organism and its apparent pathogenicity in monkeys, when the handlers did not become ill, the CDC concluded that the virus had a very low pathogenicity to humans. The Philippines and the United States had no previous cases of Ebola infection, and upon further isolation, researchers concluded it was another strain of Ebola, or a new filovirus of Asian origin, which they named Reston ebolavirus (RESTV) after the location of the incident. Reston virus (RESTV) can be transmitted to pigs. Since the initial outbreak it has since been found in nonhuman primates in Pennsylvania, Texas, and Italy. where the virus had infected pigs. In 2012 it was demonstrated that the virus can travel without contact from pigs to nonhuman primates, although the same study failed to achieve transmission in that manner between primates. According to the WHO, routine cleaning and disinfection of pig (or monkey) farms with sodium hypochlorite or other detergents should be effective in inactivating the Reston ebolavirus. If an outbreak is suspected, the area must be immediately quarantined. While pigs that have been infected with RESTV tend to show symptoms of the disease, it has been shown that dogs may become infected with EBOV and remain asymptomatic. Dogs in some parts of Africa scavenge for their food and it is known that they sometimes eat infected animals and the corpses of humans. Although they remain asymptomatic, a 2005 survey of dogs during an EBOV outbreak found that over 31.8% showed a seroprevalence for EBOV closest to an outbreak versus 9% a farther distance away.