I’m currently a second year medical student at UCLA and Hot Zone was not a required read. From what I remember from my micro class Ebola and Marburg are from the same family of viruses (Filoviruses). They are enveloped negative strand RNA (genetic material like DNA in humans) viruses. Negative strand viruses must package with it enzymes needed to turn the –strand RNA to a +strand RNA before making proteins (humans go from DNA to +RNA to proteins). The envelope around the viruses is acquired from the virus when it buds out from the host cell taking along with it some of the host cell membrane. The importance of the envelope is that it contains the proteins on it for the virus to attach to another cell and infect it. These envelopes are made of cell membrane materials that are easily degraded by detergents or when out side the host organism, much like how HIV (also an envelope virus) can’t survive out side the human body for too long. The cause of the common cold, Rhinovirus, is non-enveloped and can survive outside the host for periods of time.There was some debate in my micro class as to weather or not Ebola was airborne or not. The PhD who taught the class told us that it wasn’t, and that the mode of transmission was via close contact with body fluids. While the clinician (MD) said that there does exist some strains that are airborne but don’t infect humans. HIV is also proposed to have started in monkeys but mutated to also infect humans. Keep in mind I took micro more then 6 months ago, so anyone can correct me if I’m wrong.