Sunday, 12 October 2014

Ebola: Profile of a killer

Discovery

The year is 1976. Faces appear on Mars and Apples are no longer limited to growing on trees. Meanwhile, in Sudan and Zaire (the Democratic Republic of the Congo, in 2014) there is an outbreak of haemorrhagic fever.

Hundreds became ill. In Sudan, the death rate was more than 50%. In Zaire, it was close to 90%. A terrifying new illness was suddenly on the map.

Classification

Throughout the previous four decades, several outbreaks of Ebola have occurred. The virus has been isolated several different times, and five strains have been established.

Ebola virus (EBOV) is related to the Zaire outbreak of 1976, and is named after the Ebola River. Sudan virus (SUDV), Taï Forest virus (TAFV), Bundibugyo virus (BDBV), and Reston virus (RESTV; discovered in the US of all places) make up the other four members of the Ebolavirus genus.

These Ebolaviruses are single-stranded RNA viruses, meaning they need to hijack a cell (for example, one of our nice and cosy mammalian cells full of DNA-making machinery) in order to reproduce and spread. They belong to a larger family called the Filoviridae, known for having a long, tube-like structure.

[caption id="attachment_39" align="alignnone" width="300"]2537685236_d0d8cd70f3_z Transmission electron micrograph of Ebola, created by CDC microbiologist Cynthia Goldsmith. Image made available under Creative Commons licence[/caption]

Infection

Like all viruses, Ebola cannot replicate by itself. To accomplish this, it hijacks an animal cell – in the case of humans, it’s usually one of our epithelial cells lining our eyes, airways, or gut. Once inside the body, it finds its way into a cell by fusing to a surface protein.

The virus protein packaging contains RNA which, like our own DNA, encodes genetic instructions – in the case of Ebola, instructions for replicating itself. Our own cells read these instructions and set about replicating the virus. This period of time, known as the incubation period, can be between 2-21 days. The patient is not usually contagious until the disease symptoms start to manifest.

Symptoms

Being a virus, Ebola symptoms start out in such a way that it seems like it could become anything. Researchers characterised it in the first outbreak as being “the sudden onset of severe headache, fever, myalgia [muscle pain], and prostration [fatigue] quickly followed by profuse diarrhoea and vomiting and later in the many severe cases by haemorrhagic signs [internal bleeding]”.

It starts out a bit like the ‘flu. But if the dehydration doesn’t get you, the loss of blood likely will.

Transmission

Ebola can only be spread through physical contact, especially with semen and blood of an infected person. Due to the internal bleeding, blood often appears in the vomit and diarrhoeal produce of the victim; so they’re best avoided as well.

If a patient is lucky enough to survive a bout of Ebola, the virus can be present in their system for up to three months. Sex is best avoided during recovery as the virus can be found in patients’ semen during this time. Can’t avoid sex? Use a condom. (Given the current outbreak’s threat to all mankind, I’m sure the Catholic Church will let this one slide.)

Treatment

There is no cure for Ebola, but that does not mean there is no hope. Many of the outbreaks have occurred in Africa, where medical care is limited and unfortunately unable to cope with large outbreaks of such a serious disease.

Supportive care in the form of rehydration and blood transfusions should be provided, while dialysis and oxygenation may become necessary. Some treatments suggest transfusing blood from a patient who has recovered from Ebola, as they may have antibodies against the virus in their system.

As far as vaccines go, none have been proven to be successful. The recent Ebola outbreak in West Africa has seen experimental vaccines get tested. However, until they are distributed to a larger number of people in the worst affected areas it is unknown just how effective these vaccines are.

1 comment:

  1. […] more information on Ebola, see previous posts on this blog regarding virus profile, outbreak timeline, factbox, and interview with Dr Noel Murphy on the spread of Ebola in […]

    ReplyDelete