Overview Edit

Epidemiology Edit

Virology Edit

Transmission Edit

See also: Ebola virus disease § Transmission Animal to human transmission Edit The life cycles of the Ebolavirus The initial infection is believed to occur after an Ebola virus is transmitted to a human by contact with an infected animal's body fluids. Evidence strongly implicates bats as the reservoir hosts for ebolaviruses (however, despite considerable research, infectious ebola viruses have never been recovered from bats).[278] Bats drop partially eaten fruit and pulp, on which land mammals such as gorillas and duikers feed. This chain of events forms a possible indirect means of transmission from the natural host to animal populations.[279] As primates in the area were not found to be infected and fruit bats do not live near the location of the initial zoonotic transmission event in Meliandou, Guinea, it is suspected that the index case occurred after a child had contact with an insectivorous bat from a colony of Angolan free-tailed bats near the village.[280] On 12 January, the journal Nature reported that the virus emergence could be found by studying how bush-meat hunters interacted with the ecosystem.[281] Human to human transmission Edit Prior to this outbreak, it was believed that human-to-human transmission occurred only via direct contact with blood or bodily fluids from an infected person who is showing signs of infection, by contact with the body of a person who had died of Ebola, or by contact with objects recently contaminated with the body fluids of an actively ill infected person.[282][283] It is now known that the Ebola virus can be transmitted sexually. Over time, studies have suggested that the virus can persist in seminal fluid, with a study released in September 2016 suggesting that the virus may survive more than 530 days after infection.[113] In September 2014, the WHO had reported: "No formal evidence exists of sexual transmission, but sexual transmission from convalescent patients cannot be ruled out. There is evidence that live Ebola virus can be isolated in seminal fluids of convalescent men for 82 days after onset of symptoms. Evidence is not available yet beyond 82 days."[284] In April 2015, following a report that the Ebola virus had been detected in a semen sample six months after a man's recovery, the WHO issued a statement: "For greater security and prevention of other sexually transmitted infections, Ebola survivors should consider correct and consistent use of condoms for all sexual acts beyond three months until more information is available."[285][286] The WHO based their new recommendations on a March 2015 case, in which a Liberian woman who had no contact with the disease other than having had unprotected sex with a man who had had the disease in October 2014, was diagnosed with Ebola. While no evidence of the virus was found in his blood, his semen revealed Ebola virus RNA closely matching the strain that infected the woman. However, "doctors don't know if there was any fully formed (and therefore infectious) virus in the guy's semen." It is known that a male's testes are protected from the body's immune system to protect the developing sperm, and it is thought that this same protection may allow the virus to survive in the testes for an unknown time.[287] On 14 September 2015, the body of a girl who had died in Sierra Leone tested positive for Ebola[139] and it was suspected that she may have contracted the disease from the semen of an Ebola survivor who was discharged in March 2015.[140] According to some news reports, a new study to be published in the New England Journal of Medicine indicated that the virus could remain in the semen of survivors for up to six months,[288] and according to other researchers, the virus could continue in semen for 82 days and maybe longer. Furthermore, Ebola RNA had been found up to 284 days post-onset of viral symptoms. [289] Containment difficulties Edit One of the primary reasons for spread of the disease is the low-quality, functioning health systems in the parts of Africa where the disease occurs.[290] The risk of transmission is increased among those caring for people infected. Recommended measures when caring for those who are infected include medical isolation via the proper use of boots, gowns, gloves, masks and goggles, and sterilizing all equipment and surfaces.[291] One of the biggest dangers of infection faced by medical staff requires their learning how to properly suit up and remove personal protective equipment. Full training for wearing protective body clothing can take 10 to 14 days.[292] Even with proper isolation equipment available, working conditions such as lack of running water, climate control, and flooring have made direct care difficult. Two American health workers who contracted the disease and later recovered said that to the best of their knowledge, their team of workers had been following "to the letter all of the protocols for safety that were developed by the [CDC] and WHO", including a full body coverall, several layers of gloves, and face protection including goggles. One of the two, a physician, had worked with patients, but the other was assisting workers to get in and out of their protective gear, while wearing protective gear herself.[293] Difficulties in attempting to halt transmission have also included the multiple disease outbreaks across country borders.[294] Dr Peter Piot, the scientist who co-discovered the Ebola virus, stated that the outbreak was not following its usual linear patterns as mapped out in earlier outbreaks—this time the virus was "hopping" all over the West African epidemic region. Furthermore, past epidemics had occurred in remote regions, but this outbreak spread to large urban areas, which had increased the number of contacts an infected person might have and made transmission harder to track and break.[295] On 9 December, a study indicated that a single individual introduced the virus into Liberia, causing the most cases of the disease in that country.[296]

Containment and control Edit

Treatment Edit

Experimental treatments and testing Edit

Vaccines Edit

Further information: Ebola vaccine Several Ebola vaccine candidates had been developed in the decade prior to 2014 and had been shown to protect nonhuman primates against infection, but none had yet been approved for clinical use in humans.[406][407][408][409] According to a 2015 review article, about 15 different vaccines were in preclinical stages of development, including DNA vaccines, virus-like particles and viral vectors.[410] and another seven as yet unheard-of vaccines were being developed. Additionally, there were two phase III studies being conducted with two different vaccines. .[410] In July 2015, researchers announced that a vaccine trial in Guinea had been completed that appeared to give protection from the virus. The vaccine, rVSV-ZEBOV,[411] had shown 100% efficacy in individuals, but more conclusive evidence was needed regarding its capacity to protect populations through "herd immunity" . The vaccine trial employed "ring vaccination", a technique that was also used in the 1970s to eradicate smallpox, in which health workers control an outbreak by vaccinating all suspected infected individuals within the surrounding area.[53][54][412][413] In December 2016, the results of the two-year Guinea trial were published announcing that rVSV-ZEBOV had been found to protect people who had been exposed to cases of Ebola.[29] Of the nearly 6,000 people vaccinated, none had contracted Ebola after a ten-day period while in the group not vaccinated 23 cases developed. In addition to showing high efficacy among those vaccinated, the trial also showed that unvaccinated people were indirectly protected from Ebola virus through the ring vaccination approach, termed "herd immunity". The vaccine has not yet had regulatory approval, but it is considered to be so effective that 300,000 doses have already been stockpiled. Researchers have found the results "quite encouraging [but] there is still a lot more work to be done on vaccines for Ebola." Not yet known is the length of time that a vaccination will be effective and whether it will prove effective for the Sudan or other strains of the virus rather than only the Zaire strain, which is responsible for the West Africa outbreak.[30][414] Eventually, in April 2018 rVSV-ZEBOV Ebola vaccine was used to stop an outbreak for the first time, the 2018 Équateur province Ebola virus outbreak in the Democratic Republic of the Congo, with 3,481 people vaccinated.[415]

Outlook Edit

From the beginning of the outbreak, there existed considerable difficulty in getting reliable estimates—both of the number of people affected and of its geographical extent.[416] The three most affected countries—Guinea, Liberia and Sierra Leone—are among the poorest in the world, with extremely low levels of literacy, few hospitals or doctors, low-quality physical infrastructure, and weakly functioning government institutions.[417] One study yielded results of the spatio-temporal evolution of the viral outbreak. With the use of heat maps, it was determined that the outbreak did not uniformly unfold over the affected community areas. Growth in the regions of Guinea, Liberia and Sierra Leone was very different over time, indicating that monitoring the outbreak at district level was important. Visual inspection of incidence curves alone could not render the needed results or data; growth rates with a two-dimensional heat map were used. Finally, the study showed that accurate predictions of growth were improbable, coupled with knowledge about the disease that was not fully adequate at the time (as there were now cases of sexual transmission).[418] Statistical measures Edit Calculating the case fatality rate (CFR) accurately is difficult in an ongoing epidemic due to differences in testing policies, the inclusion of probable and suspected cases, and the inclusion of new cases that have not run their course. In August 2014, the WHO made an initial CFR estimate of 53%, though this included suspected cases.[419][420] In September and December 2014, the WHO released revised and more accurate CFR figures of 70.8% and 71% respectively, using data from patients with definitive clinical outcomes.[12][13][14] The CFR among hospitalized patients, based on the three intense-transmission countries, was between 57% and 59% in January 2015.[15] The basic reproduction number, R 0 , is a statistical measure of the average number of people expected to be infected by one person who has a disease. If the rate is less than 1, the infection dies out; if it is greater than 1, the infection continues to spread—with exponential growth in the number of cases.[421] In September 2014, the estimated R 0 were 1.71 (95% CI, 1.44 to 2.01) for Guinea, 1.83 (95% CI, 1.72 to 1.94) for Liberia, and 2.02 (95% CI, 1.79 to 2.26) for Sierra Leone.[12][422][423] In October 2014, the WHO noted that exponential increase of cases continued in the three countries with the most intense transmission.[424] Projections of future cases Edit On 28 August 2014, the WHO released its first estimate of the possible total cases from the outbreak as part of its roadmap for stopping the transmission of the virus. It stated that "this Roadmap assumes that in many areas of intense transmission the actual number of cases may be two- to fourfold higher than that currently reported. It acknowledges that the aggregate case load of Ebola could exceed 20,000 over the course of this emergency. The Roadmap assumes that a rapid escalation of the complementary strategies in intense transmission, resource-constrained areas will allow the comprehensive application of more standard containment strategies within three months." The report included an assumption that some country or countries would pay the required cost of their plan, estimated at half a billion US dollars.[297] When the WHO released these estimates, a number of epidemiologists presented data to show that the WHO projection of a total of 20,000 cases was likely an underestimate.[425][426] On 9 September, Jonas Schmidt-Chanasit of the Bernhard Nocht Institute for Tropical Medicine in Germany, controversially announced that the containment fight in Sierra Leone and Liberia had already been "lost" and that the disease would "burn itself out".[427] On 23 September 2014, the WHO revised their previous projection, stating that they expected the number of Ebola cases in West Africa to be in excess of 20,000 by 2 November 2014.[12] They further stated, that if the disease was not adequately contained it could become endemic in Guinea, Sierra Leone and Liberia, "spreading as routinely as malaria or the flu",[428] and according to an editorial in the New England Journal of Medicine, eventually to other parts of Africa and beyond.[429] In a report released on 23 September 2014, the CDC analysed the impact of under-reporting, which required correction of case numbers by a factor of up to 2.5. With this correction factor, approximately 21,000 total cases were estimated for the end of September 2014 in Liberia and Sierra Leone alone. The same report predicted that total cases, including unreported cases, could reach 1.4 million in Liberia and Sierra Leone by the end of January 2015 if no improvement in intervention or community behaviour occurred.[22] However, at a congressional hearing on 19 November, the Director of the CDC said that the number of Ebola cases was no longer expected to exceed 1 million, moving away from the worst-case scenario that had been previously predicted.[430] A study published in December 2014 found that transmission of the Ebola virus occurs principally within families, in hospitals and at funerals. The data, gathered during three weeks of contact tracing in August, showed that the third person in any transmission chain often knew both the first and second person. The authors estimated that between 17% and 70% of cases in West Africa were unreported—far fewer than had been estimated in prior projections. The study concluded that the epidemic would not be as difficult to control as feared, if rapid, vigorous contact tracing and quarantines were employed.[431]

Economic effects Edit

United Nations Development Group, improves the efficiency of UN development activities in needing countries In addition to the loss of life, the outbreak had a number of significant economic impacts. In March 2015, the United Nations Development Group reported that due to a decrease in trade, closing of borders, flight cancellations, and drop in foreign investment and tourism activity fueled by stigma, the epidemic resulted in vast economic consequences both in the affected areas and throughout Africa.[47] A September 2014 report in the Financial Times suggested that the economic impact of the Ebola outbreak could kill more people than the disease itself.[432] With regard to Ebola and economic activity in the country of Liberia, a study found that 8% of automotive firms, 8% of construction firms, 15% of food businesses and 30% of restaurants had closed due to the Ebola outbreak. Montserrado county experienced up to 20% firm closure. This indicated a decline in the Liberian national economy during the outbreak, as well as an indication that the county of Montserrado was hardest hit economically. The capital city Monrovia suffered construction and restaurant unemployment the most, while outside the capital, the food and beverage sectors suffered economically. A recuperation in the economy, at the end of the outbreak, was expected to be more rapid in some sectors than in others. Also, if the massive decline in economic activity persisted, the authors suggested a focus on economic recovery in addition to support for the healthcare system. The World Bank had projected an estimated loss of $1.6 billion in productivity for all three affected West African countries combined for 2015. In Liberian counties that were less affected by the outbreak, the number of individuals employed fell by 24%. Montserrado saw a 47% decline in employment per firm in contrast to what was obtained prior to the Ebola outbreak.[433] Another study showed that the economic effect of the Ebola outbreak would be felt for years due to preexisting social vulnerability. The economic effects were being felt nationwide in Liberia, such as the termination of expansions in the mining business. Initial scenarios had placed expected economic losses at $25 billion; however subsequent World Bank estimates were much lower, at about 12% of the combined GDP of the 3 worst hit countries.[434] The authors went on to state that social vulnerability has multiple factors and proposed a classification based on multiple variables instead of single indicators such as food insecurity or lack of hospitals, which were problems faced by rural Liberians. In spite of the end of civil violence since 2003 and inflows from international donors, the reconstruction of Liberia had been very slow and non-productive—water delivery systems, sanitation facilities and centralized electricity were practically non-existent, even in Monrovia. Even before the outbreak, medical facilities did not have potable water, lighting or refrigeration. The authors indicated that lack of food and other economic effects would probably continue in the rural population long after the Ebola outbreak had ended.[434] Other economic impacts were as follows: In August 2014 it was reported that many airlines had suspended flights to the area. [435] Markets and shops had closed due to travel restrictions, a cordon sanitaire , or fear of human contact, which led to loss of income for producers and traders. [436]

Markets and shops had closed due to travel restrictions, a , or fear of human contact, which led to loss of income for producers and traders. Movement of people away from affected areas disturbed agricultural activities. [437] [438] The FAO warned that the outbreak could endanger harvests and food security in West Africa, [439] and that with all the quarantines and movement limitations placed on them, more than 1 million people could be food insecure by March 2015. [440] By 29 July, the World Bank had given 10,500 tons of maize and rice seed to the 3 hardest-hit countries to help them to rebuild their agricultural systems. [441]

The FAO warned that the outbreak could endanger harvests and food security in West Africa, and that with all the quarantines and movement limitations placed on them, more than 1 million people could be food insecure by March 2015. By 29 July, the World Bank had given 10,500 tons of maize and rice seed to the 3 hardest-hit countries to help them to rebuild their agricultural systems. Tourism was directly impacted in the affected countries. [442] In April 2014, Nigeria reported that 75% of hotel business had been lost due to fears of the outbreak; [443] the limited Ebola outbreak had cost that country ₦8 billion. [444] Other African countries that were not directly affected by the virus also reported adverse effects on tourism. [445] [446] [447] For example, in 2015, it was reported that Gambia's tourism had fallen below 50 percent of its normal business during the same period the prior year, [448] [449] Elmina Bay in Ghana had an 80% decrease in US tourism, [450] and Kenya, [451] Zimbabwe, [452] Senegal, Zambia, and Tanzania also reported a drop. [453]

In April 2014, Nigeria reported that 75% of hotel business had been lost due to fears of the outbreak; the limited Ebola outbreak had cost that country ₦8 billion. Other African countries that were not directly affected by the virus also reported adverse effects on tourism. For example, in 2015, it was reported that Gambia's tourism had fallen below 50 percent of its normal business during the same period the prior year, Elmina Bay in Ghana had an 80% decrease in US tourism, and Kenya, Zimbabwe, Senegal, Zambia, and Tanzania also reported a drop. Some foreign mining companies withdrew all non-essential personnel, deferred new investment, and cut back operations.[438][454][455] In December 2014, it was reported that the iron ore mining company, African Minerals, had started the shutdown of its Sierra Leone operations because it was running low on income.[456] In March 2015, it was reported that Sierra Leone had begun to diversify away from mining, due to the country's recent problems.[457] In January 2015, Oxfam, a UK-based disaster relief organisation, indicated that a "Marshall Plan" (a reference to the massive plan to rebuild Europe after World War II) was needed so that countries could begin to financially assist those that had been worst hit by the virus.[458] The call was repeated in April 2015 when the most-affected West African countries asked for an $8 billion "Marshall Plan" to rebuild their economies. Speaking at the World Bank and the International Monetary Fund (IMF), Liberian president Ellen Johnson Sirleaf said the amount was needed because "[o]ur health systems collapsed, investors left our countries, revenues declined and spending increased."[459] The IMF has been criticised for its lack of assistance in the efforts to combat the epidemic. In December 2014, a Cambridge University study linked IMF policies with the financial difficulties that prevented a strong Ebola response in the three most heavily affected countries,[460] and they were urged by both the UN and NGOs who had worked in the affected countries to grant debt relief rather than low-interest loans. According to one advocacy group, "... yet the IMF, which has made a $9 billion surplus from its lending over the last three years, is considering offering loans, not debt relief and grants, in response".[461][462] On 30 January 2015, the IMF reported it was close to reaching a deal on debt forgiveness.[463] On 22 December, it was reported that the IMF had given Liberia an additional $10 million due to the economic impact of the Ebola virus outbreak.[464] In October 2014, a World Bank report estimated overall economic impacts of between $3.8 billion and $32.6 billion, depending on the extent of the outbreak and speed of containment. It expected the most severe losses in the three affected countries, with a wider impact across the broader West African region.[465][466] On 13 April 2015, the World Bank said that they would soon announce a major new effort to rebuild the economies of the three hardest-hit countries.[467] On 23 July, a World Bank poll warned that "we are not ready for another Ebola outbreak".[468] On 15 December, the World Bank indicated that by 1 December 2015, it had marshalled $1.62 billion in financing for the Ebola outbreak response.[469] On 6 July 2015, UN Secretary-General Ban Ki-moon announced that he would host an Ebola recovery conference to raise funds for reconstruction, stating that the three countries hardest hit by Ebola needed about $700 million to rebuild their health services over a two-year period.[470] On 10 July, it was announced that the countries most affected by the Ebola epidemic would receive $3.4 billion to rebuild their economies.[471][472] On 29 September, the leaders of both Sierra Leone and Liberia indicated at the UN General Assembly the launch of a "Post-Ebola Economic Stabilization and Recovery Plan".[473] On 24 November, it was reported that due to the decrease in commodity prices and the West African Ebola epidemic, China's investment in the continent had declined 43% in the first 6 months of 2015.[474] On 25 January, the IMF projected a GDP growth of 0.3% for Liberia, that country indicating it would cut spending by 11 percent due to a stagnation in the mining sector, which would cause a domestic revenues drop of $57 million.[475]

Responses Edit

Timeline of reported cases and deaths Edit

See also Edit

Notes Edit

^ [13] However, due to the estimation method used, the estimated case fatality rate (70.8%) for this particular epidemic differs from the actual ratio between the number of deaths and the number of cases. The mortality rate (death/case ratio) recorded in Liberia up to 26 August 2014 was 70%.However, due to the estimation method used, the estimated case fatality rate (70.8%) for this particular epidemic differs from the actual ratio between the number of deaths and the number of cases. ^ Tai Forest ebolavirus in Ivory Coast, which had resulted in one human transmission in 1994. There was knowledge ofin Ivory Coast, which had resulted in one human transmission in 1994. ^ 25 Oct: All governments as per WHO. ^ No change in Data from 13 May till 30 Aug ^ 29 December: All governments as per WHO. United Kingdom case dated 29 December.

References Edit