Science and health blogs are going wild. An Ebola epidemic originating in Guédeckou in southern Guinea, West Africa, is causing concern even for those many thousands of miles away. Why is this outbreak any different to the 14 other outbreaks that have occurred since the beginning of the new millenium? Is it true that the outbreak has reached Italy? Should we be worried? I’d like to think that I can help shed some light on each of these questions.
Before I dive into any speculation, it’s worth spending a moment to bring everyone up to speed about Ebola. As the name suggests, Ebola virus disease (EVD) is caused by the Ebola virus (1). Advanced symptoms of infection include vomiting, diarrhoea, and in some individuals, internal and external bleeding. This usually results in organ failure and severe dehydration, and can be fatal in up to 90% of cases.
The fatality rate of a disease isn’t the only important consideration when thinking about infectious disease – pathogens have evolved to maximise their transmission, and understanding how this occurs is essential for controlling their spread. Unfortunately, the prediction and control of the spread of Ebola is complicated by a current lack of understanding about how Ebola spreads in non-human hosts. The natural reservoir (long-term host where most of the viral population can be found) is believed to be various species of fruit bat which could be responsible for introducing Ebola to the area, although no transmission event to humans has ever been proven (2). The virus has also been shown to be carried by macaque monkeys (Philippines), and asymptomatically in pigs (Philippines and People’s Republic of China).
With regard to human-to-human transmission, Ebola virus is incredibly contagious. The virus infects new hosts via mucous membranes (e.g. mouth, urogenital tracts), across broken skin, or via contact with infected blood. However, once an outbreak has been identified, the necessity for direct contact makes control of the disease considerably easier than airborne diseases, despite the fact that symptoms may not appear for up to 21 days post-infection. Close monitoring must continue even after a patient appears to have recovered because they may remain infectious for up to 7 weeks after losing any symptoms. Unfortunately there is currently no vaccine or drug therapy available, making control of the outbreak incredibly difficult.
The current outbreak probably originated in Guinea many weeks prior to first World Health Organisation (WHO) notification on the 23rd of March which reported 49 cases and 29 deaths (3). Almost one month down the line, the WHO have reported 208 cases and 136 deaths in Guinea, including those of 16 healthworkers (4). This may seem alarming, but you only need to look back to 2007 to find a larger outbreak in the Democratic Republic of Congo (1). So why has this outbreak received so much attention?
An interview in the Independent suggests that the geographic spread of Ebola observed in Guinea is previously unprecedented, affecting a number of different towns, and even reaching across international borders into Liberia where there have been an additional 34 suspected cases (4, 5). This larger than normal coverage may be for a number of reasons. Firstly, there have never previously been any confirmed cases of the disease in Guinea, meaning that the local population are generally either unsure how to respond, or suspicious of the aid workers. Many believe that the health care workers actually harm their patients within their camps and have been blamed for bringing the disease to Guinea with them. Not only have the health workers been actively avoided by infected individuals, but violence has erupted in the Guniean city of Macenta against them (6).
However, the spread of cases into neighbouring Liberia is a far cry from recent rumours of cases in the southern Italian city of Pisa. Although by no means the source, the furthest back that I have been able to track the rumour is to Turner Radio Network, at which point I have been unable to find any further references (7). The website claimed that the virus was introduced to Italy by “40 illegal alien migrant workers“, and that “a statistical probability expert” has predicted that by the time we reach the 70th day of the outbreak the virus will have spread sufficiently that “nearly every place on the globe within 1000 miles of a commercial airport is fair game“. The article then goes on to describe how individuals should best prepare for a global pandemic.
Even if Ebola virus has reached Italy (which I doubt – see below), it is unlikely to spread in western culture. Many of the contributing factors to the spread of the disease in Guinea are irrelevant in more developed countries where healthcare workers are (generally!) respected, ill people seek help (and are more easily traced), and the dead are not touched.
To conclude this post, please allow me a small digression. While I can’t discount that the aforementioned article may be based on truth, I would argue that there are indicators that suggest that the article may not be entirely reliable, and could exhibit a degree of bias. Take from this carefully worded statement what you will, but I would always caution bloggers and readers from swallowing anything that isn’t supported by references or data, especially when something so newsworthy isn’t pounced on by other forms of media. Consider whether an author gains anything from spreading rumours (increased readership, support for a given cause, etc.) and generally consider the reputation of the author or publication. If we do not critically assess what we are reading, it is easy to disseminate false information as rumours that spread faster than the disease itself.
References
- WHO – Ebola Fact Sheet
- Vogel, G, Are Bats Spreading Ebola Across Sub-Saharan Africa? Science Vol. 344 no. 6180 p. 140 (2014)
- WHO, 23/03/14 – First notification of Ebola in Guinea
- WHO, outbreak as of 22/04/14
- The Independent, 13/04/14 – Exclusive A Medecins Sans Frontieres specialist on how the unprecedented spread of the ebola virus in west Africa makes the work of medics tougher than ever.
- The Independent, 06/04/14 – Panic as deadly Ebola virus spreads across West Africa
- Turner Radio Network, 17/04/14 – Ebola Containment lost…
Going Viral (and other Pathogens) 