October 2014 – HEALTH – The number of confirmed Ebola cases passed the 10,000 mark over the weekend, despite efforts to curb its spread. And while the disease typically dies on surfaces within hours, research has discovered it can survive for more than seven weeks under certain conditions. During tests, the UK’s Defense Science and Technology Laboratory (DSTL) found that the Zaire strain will live on samples stored on glass at low temperatures for as long as 50 days. This family includes the Zaire ebolavirus (Zebov), which was first identified in 1976 and is the most virulent; Sudan ebolavirus, (Sebov); Tai Forest ebolavirus; Ebola-Reston (Rebov), and Bundibugyo ebolavirus (Bebov) – the most recent species, discovered in 2008. For their 2010 paper, ‘The survival of filoviruses in liquids, on solid substrates and in a dynamic aerosol’, Sophie Smither and her colleagues tested two particular filoviruses on a variety of surfaces. These were the Lake Victoria marburgvirus (Marv), and Zebov. Each was placed into guinea pig tissue samples and tested for their ability to survive in different liquids, and on different surfaces at different temperatures, over a 50-day period. When stored at 4° (39°F), by day 26, viruses from three of the samples were successfully extracted; Zebov on the glass sample, and Marv on both glass and plastic.
By day 50, the only sample from which the virus could be recovered was the Zebov from tissue on glass. ‘This study has demonstrated that ﬁloviruses are able to survive and remain infectious, for extended periods when suspended within liquid and dried onto surfaces,’ explained the researchers. ‘Data from this study extend the knowledge on the survival of filoviruses under different conditions and provide a basis with which to inform risk assessments and manage exposure.’ The researchers do stress that these tests were carried out in a controlled lab environment, and not in the real world, but published their findings to highlight the survival rates. Last week the Centers for Disease Control and Prevention (CDC) updated its Ebola guidelines following the rise in infections. –Daily Mail