Ebola (EVD), also known as haemorrhagic fever, is a highly contagious disease transmitted by the Ebola virus. The virus was first described in 1976 when it was first discovered next to the Ebola River in the Democratic Republic of Congo (DRC).
The disease is caused by the Ebola virus, of the Filoviridae family, which also includes the virus responsible for Marburg fever.
Six different ebola virus species have been identified:
- Bundibugyo ebolavirus (BDBV)
- Zaire ebolavirus (EBOV)
- Reston ebolavirus (RESTV)
- Sudan ebolavirus (SUDY)
- Taї Forest ebolavirus (TAFV)
- Bombali ebolavirus (BOMV).
Only BDBV, EBOV and SUDY have been associated with large EVD outbreaks in Africa.
Ebola virus is transmitted to humans through initial contact with an infected animal, such as a fruit bat, antelope or monkey. Subsequently, the spread of the virus within the human community occurs through direct contact with organs, blood, biological fluids such as saliva, urine, semen, breast milk, and vomit, of infected individuals both living and dead, and by indirect contact with contaminated environments, surfaces, and objects.
An important area of research is still studying how long the virus can remain in some body fluids after the individual has recovered. Although no known risk of Ebola infection through causal contact with a survivor has ever been documented, the virus has been shown to be present in seminal fluid, breast milk, ocular fluid, and the spine in individuals who have survived the disease.
Serological studies have also shown the presence of the Ebola virus in dogs and cats in areas affected by the outbreak, but with no documented cases of disease or transmission.
The largest documented outbreak was in 2013 in West Africa, ending in 2016 after involving a total of 28,652 cases and 11,325 deaths in ten countries (Liberia, Guinea, Sierra Leone, Mali, Nigeria, Senegal, Spain, the United Kingdom, Italy and the United States of America).
The current outbreak in the Democratic Republic of Congo, which began in August 2018, has already caused more than 3,200 infections, including more than 2,000 deaths (WHO).
The incubation period of Ebola ranges from 2 to 21 days.
Symptoms first manifest as fever, headache, muscle pain, and general malaise accompanied by diarrhea, vomiting, and abdominal pain.
The disease progresses with the appearance of multiorgan dysfunction symptoms, including alterations in liver and kidney function, respiratory and central nervous system function, and manifestation of maculopapular rash.
More than half of patients experience hemorrhage, characterized by bleeding in the gastrointestinal tract, epistaxis, hematuria (presence of blood in urine), bleeding gums, and petechiae. Bleeding can evolve into disseminated intravascular coagulation (DIC) and multiorgan failure. In these cases mortality ranges from 25% to 90%.
Clinical diagnosis of Ebola during the early stages of the disease can be difficult because of non-specific symptoms that can be interpreted for signs of other infections.
For diagnostic suspicion of Ebola virus infection, there must be a combination of symptoms indicative of EVD and possible exposure to EVD within 21 days before the onset of symptoms. Ebola virus can be detected in the blood after the onset of symptoms (especially fever). In order to confirm diagnosis of Ebola, laboratory tests are the identification of viral antigens (ELISA), of the viral genome by PCR or isolation of the virus. In the advanced stage of the disease, on the other hand, serologic testing for IgM or IgG antibodies can be performed.
To date, there is no specific treatment for the Ebola virus. Therapy is based on support of body function and symptom containment, such as hydration and electrolyte balance, oxygen therapy, administration of blood components, antipyretics and antiemetic agents.
Since the natural host of the virus has not yet been identified with certainty, it is impossible to intervene in order to prevent future outbreaks.
Prevention and control of the virus is based on compliance with sanitation standards, early diagnosis, surveillance and traceability of contacts, safe burial practices for deceased patients, and health information and education.
Increasing awareness of risk factors for Ebola infection and protective measures that can be implemented by the community is a powerful and effective means of reducing human transmission:
- Reducing the risk of transmission from wildlife to humans by reducing contact with bats, monkeys and antelopes. Animal products should be thoroughly cooked before consumption;
- Reducing the risk of inter-human transmission by adopting appropriate personal protective equipment to care for sick individuals;
- Carrying out the safe and dignified burial of the dead;
- Educating on good personal and environmental hygiene;
- Reducing the risk of possible sexual transmission. The WHO recommends that male survivors have protected sex for at least 12 months after the onset of symptoms or until semen tests negative twice for the virus.
The experimental Ebola vaccine, rVSV-ZEBOV, was studied during the large outbreak in 2015 in Guinea, involving 11,841 people. The vaccine, which has demonstrated a high degree of efficacy, is currently being used in the ongoing Ebola outbreak in the DRC, targeting those most at risk such as health care workers or contacts of infected people.
Source: WHO, CDC,Epicentro.iss