Ebola

The Ebola virus (formerly known as Ebola hemorrhagic fever) is a serious disease, often fatal to humans.
The virus is transmitted to humans from wild animals and then propagates through human-to-human transmission.
The average case fatality rate is about 50%. During the previous outbreaks, the rates went from 25% to 90%.
The first outbreaks of Ebola disease occurred in isolated villages in Central Africa, near tropical forests, but the outbreak in 2014-2016 in West Africa affected large urban centers as well as Of rural areas.
Community participation is essential to curb outbreaks. To be effective, control must be based on a range of interventions: case management, infection control and control measures, surveillance and contact research, quality laboratory services, safe burials and social mobilization.
Early supportive care focused on rehydration and symptomatic treatment improves survival rates. No registered treatment has yet demonstrated its ability to neutralize the virus, but several treatments (blood derivatives, immunological or drug) are under study.

General information

• The Ebola virus causes an acute and severe disease, often fatal if left untreated. Ebola disease first appeared in 1976, during two simultaneous outbreaks in Nzara (today in South Sudan) and Yambuku (Democratic Republic of the Congo). Yambuku being located near the Ebola River, this one gave its name to the disease.

• The outbreak in 2014-2016 in West Africa was the largest and most complex since the discovery of the virus in 1976. It has produced more cases and deaths than all previous outbreaks combined. This outbreak also has a particular feature of spreading from one country to another, starting from Guinea to reach Sierra Leone and Liberia.

• The family of Filoviridae viruses comprises 3 genera: Cuevavirus, Marburgvirus and Ebolavirus. Five species have been identified in Ebolavirus: Zaire, Bundibugyo, Sudan, Reston and Taï Forest. The first three have been associated with major African outbreaks. The virus causing the 2014-2016 outbreak in West Africa belongs to the Zaire species.

Transmission

• Frugivorous bats of the family Pteropodidae are thought to be the natural hosts of the Ebola virus. It enters the human population after close contact with blood, secretions, organs or biological fluids of infected animals such as chimpanzees, gorillas, frugivorous bats, monkeys, antelopes Wood or porcupines found sick or dead in the rainforest.

• It is then propagated by human-to-human transmission, following direct contact (injured skin or mucous membranes) with blood, secretions, organs or biological fluids of infected persons, or with surfaces and materials Bed, clothing) that have been contaminated by this type of liquids.

• Health workers have often become infected by treating suspected or confirmed cases of Ebola disease. This has occurred in close contact with patients, when anti-infectious precautions have not been strictly applied.

• The funeral rites during which the relatives and friends of the deceased are in direct contact with the body may also play a role in the transmission of the Ebola virus.

• Affected individuals remain contagious as long as the virus is present in their blood.

Sexual transmission

• There is a need for more monitoring data and more research into the risks of sexual transmission and, more particularly, the presence of viable and transmissible viruses in sperm as a function of time. In the meantime, and based on current evidence, WHO recommends the following:

• All survivors of Ebola and their sexual partners should be advised on safer sexual practices until the sperm has given a negative test twice. Condoms will be provided to survivors.

• Men who survive in Ebola should be tested on their sperm 3 months after the onset of the disease and then for those with a positive result, test each month until they have given 2 negative tests In search of the virus in the sperm by RT-PCR, with an interval of one week between the two tests.

• Those who have survived the disease and their partners must either:

  • Refrain from sexual intercourse, or
  • Adopt safer sexual practices by using condoms correctly and regularly until the sperm has given a negative test twice.
  • When tests are negative, survivors can return to normal sexual practices without fear of transmission of the Ebola virus.
  • Based on new analyzes of current research and the reflection of the WHO Advisory Group on Action against Ebola Virus, WHO recommends that men who have survived the Ebola virus Safer sexual practices and adherence to personal hygiene rules for 12 months after the onset of symptoms or until their sperm has twice tested negative for Ebola.
  • Until their sperm has twice tested negative for the Ebola virus, men who have survived the disease must adhere to the rules of personal hygiene and hand hygiene by washing thoroughly, Water and soap after any physical contact with sperm, including after masturbation. During this period, used condoms should be handled and discarded carefully so as to avoid contact with the seminal fluid.
  • All survivors, their partners and their families must be treated with respect, dignity and compassion.

Symptoms of the Ebola virus

• The duration of incubation, ie the time elapsed between infection with the virus and the onset of the first symptoms, varies from 2 to 21 days. As long as they do not show symptoms, human subjects are not contagious. The first symptoms are febrile fatigue with sudden onset, muscle pain, headache and sore throat. They are followed by vomiting, diarrhea, rash, symptoms of renal and hepatic insufficiency and, in some cases, internal and external bleeding (eg bleeding gums, blood in the stool). Laboratory tests revealed a decrease in leukocyte and platelet counts, as well as an increase in liver enzymes.

Persistence of virus in people recovering from Ebola virus

• It is known that Ebola virus persists in the immune-privileged sites of subjects who have recovered from the Ebola virus: testis, inner eye and central nervous system. In women who have been infected during pregnancy, the virus persists in the placenta, amniotic fluid and fetus. In women who have been infected during breastfeeding, the virus may persist in breast milk.

• Studies on viral persistence indicate that in a small proportion of survivors, some biological fluids may give a positive RT-PCR (reverse transcriptional gene amplification) test for Ebola virus for more than 9 months.

• A symptomatic relapse in a subject who has recovered from the Ebola virus due to increased replication of the virus in a specific site is a rare but attested event. The reasons for the phenomenon are not yet fully understood.

Diagnostic

• Ebola disease can be difficult to distinguish clinically from other infectious diseases such as malaria, typhoid fever and meningitis. The following diagnostic methods are used to confirm that infection with the Ebola virus is the cause of the symptoms:

  • Enzyme immunoassay (ELISA);
  • Antigen capture detection tests;
  • Serum neutralization test;
  • Reverse transcription followed by polymerase chain reaction (RT-PCR);
  • Electron microscopy;
  • Isolation of the virus on cell culture.

• Careful attention should be given to the selection of diagnostic tests, taking into account the characteristics The incidence and prevalence of the disease, as well as the social and medical implications of the results. It is strongly recommended to consider the use of diagnostic tests, which may have had an independent and international assessment.

• The tests currently recommended by WHO are:

  • Automated or semi-automated nucleic acid (NAT) testing for routine diagnostic management.
  • Rapid antigen tests for use in isolated locations or NAT are not readily available. These tests are recommended for screening purposes as part of surveillance activities; The positive tests must nevertheless be confirmed by NAT.

• The preferred samples for diagnosis are:

  • Total blood taken from EDTA in living patients with symptoms.
  • Sample of liquid taken from the oral sphere and stored on universal transport medium in deceased patients or if blood sampling is not possible.
  • Samples from patients present an extreme biological hazard. Therefore, laboratory analyzes performed on non-inactivated samples should comply with the most stringent confining conditions possible. All biological samples must be placed in a triple pack (3 layers) for national or international transport.

Treatment and Vaccines

• Oral or intravenous support rehydration and the treatment of specific symptoms improve survival rates. No treatment available has yet been proven against the Ebola virus. Nevertheless, a range of potential treatments, including blood products, immune therapies and drug treatments are being evaluated.

• An experimental anti-Ebola vaccine proved to be very protective against this deadly virus in a major trial in Guinea. This product, called rVSV-ZEBOV, was studied in a trial involving 11,841 people in 2015. Of the 5837 people vaccinated, no case of Ebola virus disease was recorded 10 days or more after vaccination. In comparison, there were 23 cases in the control group who did not have the vaccine after 10 days or more.

• The trial was conducted by WHO, with the Guinean Ministry of Health, Médecins sans frontières and the Norwegian Institute of Public Health, in collaboration with other international partners. A ring vaccination protocol was chosen for the trial, with some circles vaccinated shortly after the detection of one case and others within 3 weeks.

Prevention and control

• To effectively combat the outbreak, a range of interventions must be implemented: case management, surveillance and contact research, quality laboratory services, safe burials and social mobilization. Community participation is essential to curb outbreaks. Sensitization to risk factors for Ebola infection and possible protective measures (including vaccination) is an effective way to reduce transmission to humans. Risk reduction messages should address the following factors:

• Reduced risk of transmission between wild animals and humans through contact with infected fruit bats or monkeys / primates and by consumption of their raw meat. Handle animals with gloves and wear suitable protective clothing. Products derived from these animals (blood and meat) must be cooked thoroughly before being eaten.
  Reduced risk of human-to-human transmission from direct or close contact with subjects with Ebola symptoms, particularly with their body fluids. Gloves and appropriate personal protective equipment should be worn when caring for the sick at home. It is also necessary to wash the hands systematically after visiting patients in the hospital or after caring for patients at home.

• Reduction of the potential risk of sexual transmission since it is not possible to rule out any risk of transmission, men and women who have survived the Ebola virus must refrain from any type of sexual intercourse Anal or bucco-genital) for at least 12 months after onset of symptoms. If sexual abstinence is not possible, male or female condoms should be used. Contact with body fluids should be avoided and washing with soap and water should be avoided. WHO does not recommend isolating convalescent male or female patients whose blood tests have given negative results for the Ebola virus.
  Outbreak containment measures including the rapid and safe burial of the deceased, identification of subjects likely to have been in contact with a person infected with the Ebola virus, monitoring of the state of health of the contacts For 21 days, separating healthy / diseased subjects to prevent spread, good hygiene and maintaining a clean environment.
  Infection Control in Health Care Settings

• Health care workers should always apply standard precautions when caring for patients, regardless of the presumed diagnosis. These precautions include basic hand hygiene, respiratory hygiene, personal protective equipment (to protect against splashing or other contact with infected material), and Injections and funeral rites.

• Health workers who deal with suspected or confirmed cases of Ebola infection should take additional infectious measures in addition to the usual precautions to avoid contact with blood or body fluids Of the patient or with contaminated surfaces and materials such as clothing and bed linen. In close contact with patients (ie less than one meter), they must wear a facial protection (or surgical mask and goggles), a clean, non-sterile Long sleeves, and gloves (sterile for certain medical procedures).

• Laboratory staff are also at risk. Specimens that have been taken from human subjects or animals for Ebola virus infection should be handled by trained personnel and treated in adequately equipped laboratories.

Year	Country	Virus	Number of cases	Number of deaths Case	fatality rate
2015	Italy	Ebola Zaire	1	0	0%
2014	Democratic Republic of the Congo	Ebola Zaire	66	49	74%
2014	Spain	Ebola Zaire	1	0	0%
2014	United Kingdom	Ebola Zaire	1	0	0%
2014	USA	Ebola Zaire	4	1	25%
2014	Senegal	Ebola Zaire	1	0	0%
2014	Mali	Ebola Zaire	8	6	75%
2014	Nigeria	Ebola Zaire	20	8	40%
2014-2016	Sierra Leone	Ebola Zaire	14124*	3956*	28%
2014-2016	Liberia	Ebola Zaire	10675*	4809*	45%
2014-2016	Guinea	Ebola Zaire	3811*	2543*	67%
2003 (Nov- dec)	Congo	Ebola Zaire	35	29	83%
2003(Jan- April)	Congo	Ebola Zaire	143	128	90%
2001-2002	Congo	Ebola Zaire	59	44	75%
2001-2002	Gabon	Ebola Zaire	65	53	82%
2000	Uganda	Ebola Sudan	425	224	53%
1996	South Africa	Ebola Zaire	1	1	100%
1996 (Jul-Dec)	Gabon	Ebola Zaire	60	45	75%
1996 (Jan-Apr)	Gabon	Ebola Zaire	31	21	68%
1995	Democratic Republic of the Congo	Ebola Zaire	315	254	81%
1994	Côte d'Ivoire	Ebola Taï Forest	1	0	0%
1994	Gabon	Ebola Zaire	52	31	60%
1979	Sudan	Ebola Sudan	34	22	65%
1977	Democratic Republic of the Congo	Ebola Zaire	1	1	100%
1976	Sudan	Ebola Sudan	284	151	53%
1976	Democratic Republic of the Congo	Ebola Zaire	318	280	88%

• Number of suspected, probable and confirmed cases

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WHO prevention and control guide