Hey Tricky. My PhD is in bacteriology as well. I am in my second year. Techniques for bacteriology and virology can be similar and then different depending on what type of virus you are working with. Alot of research will involve molecular techniques such as PCR and cloning. The basic principles will be common to both research areas. Depending on the area of research there may be protein assays, infection studies in-vitro and in-vivo, confocal microscopy etc. Basically, you will be in the lab alot. My friends doing virology and me doing microbiology chose to do our PhD's in this area as we are interested in disease and the mechanisms surrounding it. I think as long as you have an idea of what you are getting yourself into and you enjoy it, then you should be fine. What are you interested in?