Welcome to our learning unit on the epidemiology of Ebola virus disease. This short introductory video, I'd like to talk you through some of the highlights of this learning unit. So, Ebola virus belongs to the family of the Filoviridae, and this consists of the genuses Ebola and Marburg viruses. They belong to the order of Mononegavirales, and these are considered as being amongst the most virulent pathogens in humans and non-primates. The Ebola virus is a non-segmented rope-like negative stranded RNA virus with a genome of approximately 19 kilobases that resembles rhabdoviruses and paramyxoviruses in a genome organization and replication mechanisms. We usually tend now not to use the term haemorrhagic fever any longer to describe the disease caused by Ebola virus because we have learned that at least during the latest outbreaks, only a small proportion of Ebola patients actually develop clinical signs of hemorrhage and significant bleeding. If we examine the virus under the electron microscope, we see that it has a characteristic filamentous or rope-like structure as well as the other Filoviridae to the other Marburg virus actually, and it may come in various shapes. It may coiled up and it may form shapes such as a U-shape, a six or anything else and part of the virus will be long and stretched out, whereas other parts will be coiled up. There are five various, five different species of Ebola virus. Actually the Zaire Ebolavirus, the Sudan ebolavirus, Tai Forest Ivory Coast ebolavirus, the Bundibugyo vebolavirus, and then Reston virus which so far has only been identified in macaques and then Maine in experimental or in laboratory infections actually, and the Reston virus are the only one which we do not find in Africa. Amongst the four viruses which have been identified in Africa causing human disease, the Zaire ebolavirus has been responsible for most outbreaks and is considered most virulent. The first Filovirus infection which was discovered actually or which cause disease and where the Filoviruses were for the first time identified with the outbreak of Marburg virus actually in a couple of laboratory workers at the University Hospital of the small university town of Marburg in Germany. That was in 1967. Ebola virus was identified first in two outbreaks, the two outbreaks occurred in Zaire and Sudan in 1976 actually. If you look at the map of Africa, we see that most of the outbreaks really focus on the central African dense rainforest belt and adjacent areas actually. Usually, these outbreaks occurred in remote settings in small villages, small communities which were not easily accessible, which also offers already a hint to why most of these outbreaks have been very circumscript. As we can see, there are outliers and the most important outlier, is now the- in geographical terms is now at the outbreak area in West Africa, actually. Now the current outbreak began in Guinea, in the border region to Sierra Leone and Liberia, and then rapidly spread into the two adjacent countries. Of course as we know, there has been some spillover cases in Mali, some cases in Nigeria actually, which were quite rapidly contained so that the current outbreak really focused on these three countries, actually. At the time of speaking, which is in the beginning of March 2015, the epidemic has declined or is in decline and we do see dwindling numbers of the disease in Guinea, in Sierra Leone, and in Liberia, with most active transmission still going on in Sierra Leone and at the time of speaking, it is not entirely forseeable whether the epidemic will level off within the next one or two months or whether we will have to witness more cases in the months to come, actually. Now, what is for sure is that the epidemiology of course is continuously changing. The peak of transmission have been reached in the beginning, towards the middle of the second half of 2014, and what we now see is that what's the probable end of the outbreak that numbers are not continuously leveling off. But with better tracking case detection, better epidemiological tracing, fully fledged treatment units in place in all three countries, actually, we do see that there are every now and then new clusters of cases which occur. But the general tendency is that as far as we can say, the outbreak is now leveling off. Thank you very much. This should serve as a brief introduction to your learning unit which I hope you will enjoy. Thank you.
