Sunlight-mediated disinfection of viruses in surface water:

...The role of reactive oxygen speciesDr. Tamar Kohn, Institute of Environmental Science and Technology, Swiss Federal
Institute of Technology Lausanne (EPFL), SwitzerlandAbstract:Waterborne pathogens in drinking and recreational water present a serious threat to public health worldwide. Pathogens enter water sources via the discharge of inadequately treated and raw wastewater. The situation is especially acute in developing countries, where an estimated 2.6 billion people lack access to proper sanitation facilities. Industrialized
nations have also recognized waterborne pathogens as an emerging water quality problem. Up to 9 million cases of waterborne illnesses are estimated to occur annually in the US alone. Alarmingly, waterborne disease outbreaks are directly related to heavy rainfall events and are therefore considered a growing public health risk associated with the anticipated effects of global warming.Pathogenic viruses present a particular challenge for microbial water quality
because they are excreted in very high numbers from infected patients, while their infectious dose can be very low. In surface water, sunlight-mediated disinfection is an important factor governing the survival of viruses. This naturally occurring disinfection process is also exploited for engineering applications, such as waste stabilization ponds. Sunlight-mediated inactivation can occur directly, via damage to nucleic acids by UVB
light. In addition, inactivation can result from indirect damage of virus components by reactive oxygen species formed in the presence of sunlight and oxygen and sensitizers in the surrounding water sample (exogenous inactivation). While the role of direct damage has long been recognized, only little is known about the contribution of exogenous inactivation to overall virus disinfection.The goal of my work is to develop a quantitative and mechanistic understanding of exogenous virus inactivation in sunlit water. In experiments using a solar simulator, we investigated the sunlight-mediated inactivation of coliphages MS2 and PhiX174, two commonly used surrogates for human viruses. In this presentation I will illustrate the importance of different reactive oxygen species on virus survival and I will discuss the
mechanisms which cause the viruses to lose infectivity. In addition, I will demonstrate how we are using this information to develop novel methods to distinguish between viable and inactivated viruses.

Location: Kaprielian Hall (KAP) - 209

Audiences: Everyone Is Invited

Contact: Evangeline Reyes