Chances of Ebola spreading in developed world are extremely low

Yesterday's declaration by the World Health Organisation that the Ebola outbreak in west Africa represents a public health emergency of international concern is a recognition that the infectious disease is well out of control in the region. So what are the chances of the virus breaking out of Africa and spreading to Europe and North America?

An emergency WHO committee concluded that “the possible consequences of further international spread are particularly serious in view of the virulence of the virus, the intensive community and health facility transmission patterns, and the weak health systems in the currently affected and most at-risk countries”. It added that a co-ordinated response was essential to reverse the international spread of Ebola.

The number of cases stands at 1,779, with some 961 people known to have died from the virus. The epidemic began in Guinea, where most deaths have occurred, and has spread to Liberia, Sierra Leone and Nigeria.

A type of haemorrhagic fever, Ebola virus emerged in 1976 in what is now the Democratic Republic of Congo. There have been several major outbreaks since, with the most severe registering fatality rates in the region of 90 per cent. However, this is the first outbreak to have taken hold in urban areas, where population density and mobility mean a greater likelihood of human- to-human transmission.

Worrying features

Other worrying features of the outbreak that have almost certainly contributed to its protracted nature are the especially virulent subtype of Ebola involved; a greater population density in this part of Africa; and the fact that it has taken hold over a wide geographical area.

The main reservoir for Ebola is thought to be a type of bat that lives in the region’s rainforests. There is a mistaken belief that the virus is harboured by monkeys; however, all primates contract the virus when they handle blood and other bodily fluids of infected animals. Human-to-human transmission occurs when an infected person’s bodily fluids enter the next victim’s broken skin or mucous membranes.

The symptoms of Ebola are similar to a flu-like illness, with a high temperature, muscle aches and fatigue. Patients are weak and very ill but, contrary to popular bel- ief, they do not die by exsanguination. They may have blood in their stools or vomit, but tales of people “bleeding out” through their eyes and nose are wide of the mark.

Although Ebola has a very high fatality rate, the overall number of deaths is relatively low compared with malaria deaths. Compared with a virulent influenza outbreak, Ebola is far less contagious.

This makes it an unlikely threat to the developed world. Yes, cases may be diagnosed in Europe as a result of air travel from west Africa and possibly in healthcare workers, but the chances of the virus spreading from person to person in the developed world are extremely low.