A Look at the Ebola Virus

Ebola virus got its name from the river where the first outbreak emerged - the Ebola River in the Democratic Republic of the Congo (formerly Zaire) in Africa. In 1976 simultaneous outbreaks occurred in Sudan and Zaire causing hundreds of deaths. Infact more than 400 people were killed. The Zaire subtype was the most deadly with a 90% mortality rate. About 50% of those who contracted the Sudan subtype died.

According to the World Health Organisation there are five species of Ebola virus - Zaire, Sudan, Cote d’Ivoire, Bundibugyo and Reston - and they belong to the ribonucleic acid family, the Filoviridae.

Ebola haemorrhagic fever is a highly contagious disease. Ebola symptoms occur 2-21 days after infection, although it is common for symptoms to appear within the first week - they include a sore throat, headache, fever, vomiting and bloody diarrhoea. Then the individual may bleed internally from major organs or blood vessels and the digestive tract. The blood loss can be so severe that it eventually causes shock to the body and respiratory failure, and in many cases this quickly leads to death.

Ebola can be transmitted in a number of ways; by direct contact with the blood, secretions or other bodily fluids of an infected person. Health officials treating Ebola patients have been prone to infection and in some cases so have people who've attended the funerals of Ebola victims.

The Ebola virus is a serious threat. It hijacks host cells and its mission is to replicate itself, and in the process it destroys host cells. It’s a filamentous viral particle with a hook or loop at one end.

Once inside the body it uses glycoprotein spikes to latch onto cells and mediate fusion between the viral envelope and host cell membranes. This is the front door that the virus needs through which it can release its contents into the host cell cytoplasm (Yoshihiro Kawaoka, N Engl J Med, 23 June 2005). Once inside the Ebola virus particles begin to replicate like crazy and they quickly overwhelm the protein synthesis apparatus of infected cells, as well as host immune defences. There is also some evidence that the host's immune system contributes to the fatal effects of the fever as increased levels of inflammatory cytokines and tumor necrosis factor alpa have been associated with Ebola virus deaths (Nancy Sullivan et al, J of Virology, September 2003, p.9733-9737, Vol.77, No.18).

Currently there is no cure or vaccine for Ebola virus and its exact origin and natural reservoir have so far not been identified. Many researchers point to the rainforests on the African continent and in the Western Pacific. Non-human primates are not suspected of being the reservoir.

It is also a hard organism to study as a) it's extremely dangerous and b) only appears sporadically. But Yoshihiro Kawaoka and his team at the University of Wisconsin at Madison claim to have created a harmless version that they can work with to find a cure or vaccine.