A close-up of the Ebola virus (colourised), taken using an electron microscope

Ebola: all you need to know

Since the end of last year, the most deadly outbreak of Ebola to date has been sweeping through parts of West Africa. But what is it, and could it spread to the UK? Here's your complete guide to this violent and destructive disease.

Since the end of last year, the most deadly outbreak of Ebola to date has been sweeping through parts of West Africa. Almost one-and-a-half thousand people have been infected and there have been nearly 900 deaths. But what is Ebola, and could it spread to the UK? Here’s your complete guide to this violent and destructive disease.

Advertisement

What is Ebola?

Ebola virus disease is a severe tropical fever caused by a group of four viruses that are renowned as being amongst the most dangerous and most deadly viruses on the planet.

Why is it in the news?

The outbreak currently raging in West Africa is the deadliest on record since the discovery of the virus in 1976. It began in the eastern rainforest region of Guinea before spreading to the neighbouring countries of Sierra Leone and Liberia. Heading east along the coast, Nigeria has also seen a few cases in Lagos, its largest and most populous city.

Media focus on Ebola has exploded recently, in part due to suspected cases in places like Hong Kong, New York City, Saudi Arabia and even at Gatwick Airport here in the UK, where a passenger arriving from Sierra Leone collapsed and died in the terminal upon arrival. These incidences, which have not been confirmed as Ebola-related, have fuelled speculation about whether the disease could spread across the oceans to the Americas or Europe.

What happens if you get it?

Contrary to popular belief, you do not have a 90% chance of dying. The mortality rate changes with each outbreak, depending on the strain of the virus and the outbreak’s conditions. Mortality rates of past outbreaks have ranged from 25% to 90%, and the rate of the current outbreak is presently around 55%.

The sole aim of any virus is to replicate and make copies of itself. Ebola viruses can take two to 25 days to produce enough copies and do enough damage to cause a person to start displaying symptoms. Until they start showing symptoms, a patient is not infectious.

The virus seems to infect a wide variety of cell types throughout the body, but has a slight penchant for cells in connective tissue. This gives the virus easy access to the bloodstream in which it releases a special protein that causes blood vessels to become leaky and blood clotting to fail.

Cells infected by the Ebola virus go into a panicked state and can start pumping out vast amounts of cytokines (a type of small protein), which themselves can cause serious damage to the sufferer’s body tissues and organs.

So what exactly are the symptoms?

Initially the disease looks similar to other tropical fevers such as malaria or dengue. The patient is tired, has a headache, joints and muscles ache, and he or she generally feels terrible. Diarrhoea and vomiting begin rapidly after the first stage.

Once the final and most violent phase begins, the condition is unmistakable. There is severe internal bleeding, patients begin vomiting blood, the eyes become bloodshot, and even the gums begin to bleed. Blood loss is the most common overall cause of death. Loss of too much blood can cause organ failure, breathing difficulties and send the patient into shock.

How is Ebola spread?

Ebola can spread via any of an infectious person’s bodily fluids: vomit, blood, sweat, urine, semen, saliva and stool. Any object that may have been contaminated with these fluids is also out-of-bounds as the virus can survive for up to a few days outside of a host, depending on the temperature.

How is it treated?

There is currently no fully approved treatment or vaccine available.

However, some success has recently been seen with a treatment called the ZMapp serum. This mixture of three antibodies was given to two USA aid workers who became infected with Ebola in late July. The treatment, which has not yet been shown to be safe for use in humans, was approved in this instance only under the ‘compassionate use’ regulation set out by the US Food and Drug Administration. It works by binding to sugar molecules present on the outside of the virus, stopping the virus from entering and infecting new cells. This provides what’s known as ‘passive immunity’, which gives immediate protection that isn’t long lasting. For a more long-term solution, a vaccine is required.

“There is a decent catalogue of experimental molecules,” says Dr Derek Gatherer, a virologist at Lancaster University. “ZMapp has been pulled out of the bottom drawer as there has been a big media splash in the USA. I don’t imagine the rest of us will see it on the shelves for quite some time.”

There are a few Ebola vaccines in development, with one from the USA’s National Institute of Health set to begin clinical trials this September. “Maybe by Easter next year the NIH will be able to come out and say that the vaccine has passed phase I [initial clinical trials in healthy volunteers to test the safety of the vaccine]. The question then becomes how soon do we go to phase II [larger trials to determine if the vaccine is effective]? This is much more difficult as you need volunteers who are at risk of the disease. The placebo group is going out unprotected, and they don’t know that. There are difficult ethical decisions that need to be made here,” says Gatherer.

What’s the likelihood of it spreading further?

The overall consensus is that Ebola is unlikely to spread and, if it does, countries outside Africa are expected to be able to handle the situation.

“I think an actual outbreak in the UK, in the sense that the disease would be in the general population and people would be catching it on buses and the street, is extremely unlikely,” says Gatherer. “If [Ebola] did establish itself in Nigeria, and we had an urban focus in Lagos like we have in [Guinea], then there would be more [infected] air travellers turning up in Britain, simply because Lagos is a much bigger air hub.”

However, any outbreaks in the UK could be contained by simple public health measures, such as patient isolation. Due to its fast-acting and destructive nature, the virus will eventually burn itself out as it kills or is driven out of all the available hosts in the area.

If simple public health measures can be used to control Ebola, how do outbreaks become established in places like West Africa?

“As Médecins Sans Frontières say, soap and education. The problem is that with the lack of clean water, many people simply don’t have the option of showering twice a day or washing their hands before meals,” says Gatherer. “A recent study correlated the dates of infections with the onset of the dry season… perhaps people cannot get access to enough water, so hygiene takes a nosedive as the dry season kicks in.”

Update (Friday 8 August): There have now been over 1700 confirmed cases of Ebola in West Africa and over 930 deaths.

The World Health Organization (WHO) has declared the outbreak an international health emergency and called for greater international work to control the spread of the disease. The WHO Director-General Dr Margaret Chan has, however, ruled out a ban on general international travel. There remain no confirmed cases of Ebola outside of West Africa.

By David Busse


Advertisement

Follow Science Focus on TwitterFacebook, Instagram and Flipboard