Ebola was first discovered in the Democratic Republic of Congo, then Zaire, in the 1970s, and since then there have been many outbreaks of the virus. The current epidemic, hitting primarily three countries of West Africa, is the worst the world has known.
What is Ebola?
Ebola is a virus that multiplies rapidly in the body, compromising the immune system and in many instances leads to haemorrhaging and death through shock and multiple organ failure.
Though it is unclear how the virus first transmits from animal to human cells, it is thought to occur through direct contact with an infected animal host or its bodily fluids, or consumption of its raw meat. Only mammals seem to be susceptible to the disease and are able to spread the virus, and host species include non-human primates and duikers.
According to the Public Health Agency of Canada, asymptomatic infection is possible in domestic dogs if they have come into direct contact with the bodily fluids of infected hosts.
Who is and is not at risk?
The epidemic that erupted in three West African countries earlier this year is the worst the world has known. While the World Health Organisation (WHO) was close, in mid-October, to calling an end to the outbreaks in Nigeria and Senegal, it was expecting a dramatic increase in cases in the hard-hit countries of Guinea, Liberia and Sierra Leone.
So how to know who is and is not at risk? Firstly, it is important to put the numbers into perspective. Even if there are thousands – or tens of thousands – of deaths, and each one is an individual tragedy, it is important to measure this against the continent’s estimated 1.13 billion population.
Second, transmission is by direct contact only. It is not an air-borne disease meaning that, while slight direct contact can cause transmission, only those in direct contact are at risk, primarily healthcare workers and the caregivers of those infected with the virus. By early October, of 401 known cases of healthcare workers being infected, there had been 232 deaths.
Ebola is difficult to diagnose, because the initial symptoms of the virus are general and mimic those of more common diseases, such as malaria and typhoid fever. These include a high temperature (about 38.6°C), headaches, muscle pain, diarrhoea, vomiting and abdominal pain.
Less common symptoms include a sore throat, rash, infection of the eye membranes and bleeding. Later symptoms include shock, blood coagulation disorders and secondary infections.
Four to five days after symptoms first become apparent, an Ebola patient is likely to experience the haemorrhagic effects of the virus, including pharyngitis, bleeding gums, mouth or lip ulcers, vomiting blood, passing bloody faeces or urine, nose bleeds and vaginal bleeding. In its final stages the virus can affect the central nervous system, liver and kidneys, and lead to severe bleeding and multiple organ failure.
Ebola has a two to 21-day incubation period, but symptoms usually present within eight to ten days. It is only once patients begin to show symptoms of the virus that they can transmit the virus; during the incubation period they are not contagious.
Conclusive diagnosis of an Ebola case can only be made through laboratory tests, which can be conducted within days of patients becoming symptomatic and have a rapid turn-around time. Such tests detect viral RNA, antibodies or viral antigens, and Ebola particles in tissue and cells.
How does Ebola spread?
Ebola is transmitted to humans by direct contact – through broken skin or unprotected mucous membranes – with the blood or bodily fluids of a symptomatic person or animal, or with the blood or bodily fluids of a person or non-human primate who has succumbed to the virus. Most commonly, it is transferred through contact with faeces, blood and vomit, but the virus is also present in urine, semen and breast milk.
Though studies have been conducted on the likelihood of transmission through saliva – the virus has been found in the saliva of patients at an advanced stage of the disease – these have been not been conclusive.
As long as blood and bodily fluids contain the virus, a patient may transmit the disease; once a patient has recovered, as determined by testing, he or she is no longer contagious. However, the virus has been found in semen between 61 and 82 days after the patient has presented as symptomatic, and the virus has been transmitted through semen seven weeks after recovery. For this reason, abstinence or the use of condoms are recommended during this period.
Patients who survive the virus develop an immunity to Ebola that has been found to last for at least 10 years, though it is unclear whether they are immune to all strains of the virus or whether this immunity offers them life-long protection.
The Ebola virus can survive outside a host for a limited period. According to the US Centers for Disease Control, Ebola can survive for several hours on dried surfaces, and for several days at room temperature in bodily fluids. This means transmission can occur through direct contact with contaminated surfaces and objects, but this carries a lower risk, and adequate disinfection and cleaning of surfaces reduces risk further. The point is not uncontested: the CDC also recently reported that the spread of the virus through contaminated surfaces “has not been established” – but that disinfecting procedures should be carried out nonetheless.
Ebola cannot be spread by mosquitoes.
Is Ebola airborne?
Despite fears to the contrary, Ebola is not airborne – and it is unlikely to become so.
For a virus to be classified as airborne, an individual needs to inhale a sufficient viral dose from dried droplets of mucous suspended in the air to be infected. Though viruses such as measles, chickenpox and tuberculosis transmit in this way, decade-long studies on Ebola have not observed similar patterns of transmission.
Furthermore, patients suffering from Ebola rarely cough and sneeze, making such forms of transmission even less likely. According to a former US Food and Drug Administration deputy commissioner, Dr Scott Gottlieb, “To be spread through the air, it also generally helps if the virus is concentrated in the lungs of affected patients. For humans, this is not the case. Ebola generally isn’t an infection of the lungs. The main organ that the virus targets is the liver. That is why patients stricken with Ebola develop very high amounts of the virus in the blood and in the faeces, and not in their respiratory secretions.”
The WHO notes that while it is theoretically possible for an individual with a respiratory condition to infect someone else through coughing or sneezing directly onto mucous membranes or broken skin, no studies have found this to be the case.
The virus is also very unlikely to become airborne. Scientists have found no virus that has mutated to the point where its method of transmission is significantly altered.
How to treat Ebola
There is no vaccination against Ebola, and no drug to cure the disease. At present, recovery seems to depend on early supportive care, such as the provision of intravenous fluids or rehydration solutions that contain electrolytes. Treating secondary infections, brought on as the patient’s immune system is compromised, can also aid recovery.
There are various drugs and vaccines under development, but they have not yet undergone sufficient testing in humans to determine their efficacy or safety for use in humans, beyond use for “compassionate care”. Curative drugs need to go through a process of clinical trials, in which the effects in treated and untreated individuals are compared, and possible adverse side-effects are noted.
The drug ZMapp, developed by Mapp Biopharmaceutical, is probably the best known of the drugs being developed, but it is still in the experimental phase; various other companies are in the early stages of developing treatments. Furthermore, supplies of experimental drugs that have been used to some effect are limited or exhausted.
Given their immunity to the disease, Ebola survivors’ blood is also being tested for antibodies to the virus. Experts attending a WHO-convened meeting in Geneva in September agreed to prioritise investigations around “convalescent blood”, but issues surrounding efficacy, safety and feasibility have yet to be determined.
Vaccinations are in development in the US, UK and Canada, with the hope that 20,000 doses will be available by early 2015.
Controlling the spread of the virus
While there is no cure for Ebola, the spread of the virus can be controlled through various means, including the decontamination of floors and visibly contaminated surfaces with hospital-grade disinfectants, such as household bleach. Blood and bodily fluids should be cleaned by flooding affected areas with dilutions of household bleach for 10 minutes.
The virus is also sensitive to heat and can be neutralised by heating objects for 30 to 60 minutes at 60°C or boiling them for five minutes.
Furthermore, sick individuals should be cared for in hospitals rather than in their homes. There, they can be isolated and treated by professional healthcare practitioners wearing suitable protective gear. If patients are to undergo homecare, health authorities should be notified in order to provide information and training in transmission prevention.
The WHO further recommends that protective clothing and gloves should be used in funeral and burial rituals where there is direct contact with the deceased – but it is advisable for trained professionals to take charge.
Alcohol-based hand sanitizers or the use of soap and running water should be used to clean hands after exposure to risk and coming into contact with potentially contaminated surfaces or objects.
Countries with adequate healthcare systems can control the spread
While events in hospitals in Europe and the United States have shown it is possible for person-to-person transmission to take place in some of the most prepared establishments, overall the lesson of the outbreak is that countries with adequate healthcare systems can control the spread.
Nigeria and Senegal have both seen a number of infections in 2014 but by following WHO guidelines have managed, to date, to keep the outbreaks under control. The crisis in the three most hard-hit countries to date appears to have been allowed, in part, by the paucity of healthcare provision in those countries. According to the WHO, hospitals in Liberia and Sierra Leone in particular have been overwhelmed: in early October, Liberia had 620 of the estimated 2,930 beds required for sick patients; Sierra Leone had 304 beds to cater for its 1,148-odd cases.
What if you have travelled to an Ebola-affected area?
If you have been in a country affected by Ebola, you should monitor your health closely during the incubation period. If you develop any of the symptoms of the disease in this period, you should contact your healthcare practitioner. During this time, limit your contact with other people, and contact your doctor to explain your symptoms and recent travels before going to a healthcare facility; doing so will expedite correct treatment and protect others from possible infection.
Do not rely on rumoured curatives. At this stage, there is no clinically proven effective drug and no vaccination for the disease. A rumour in Nigeria that drinking salt water would offer protection from Ebola, for example, resulted in the deaths of two people.
Edited by Julian Rademeyer
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