In this 2007 image. Centers for Disease Control (CDC) microbiologist. and Special Pathogens Branch staff member. Dr. Scott Smith could be seen manipulating a flask of cells. from which he was pipetting a sample. which would be used in experiments with live viruses. Dr. Smith was working within the confines of an enclosed flow hood. within which was created a negatively-pressurized environment. thereby. drawing laboratory room air back into the hood. rather than allowing air from within the hood to re-enter the laboratory area. Note that Dr. Smith is wearing an air-tight. self-contained. positively-pressurized suit. which kept him free of possible contamination while he carried out his experiments. The Special Pathogens Branch's (SPB) charter is the study of highly infectious viruses. many of them causing hemorrhagic manifestations in humans. Our daily work involves the investigation of viruses such as Ebola hemorrhagic fever. Marburg hemorrhagic fever. Lassa fever. Rift valley fever virus. Crimean-Congo hemorrhagic fever virus. arenaviruses and hantaviruses. and other recently identified and emerging viral diseases.