Infections can take many forms, but they do not take place in two dimensions. Nonetheless, most tissue culture systems look at the interaction of pathogens with a single flat layer of cells. On page 791, Cheryl Nickerson argues that using the rotating wall bioreactor and other three-dimensional culture systems can provide insight into pathogenic mechanisms that cannot be obtained with two-dimensional systems.
On a population scale, infections such as HIV, influenza and severe acute respiratory syndrome (SARS) can be transmitted from one species to another. Some viruses need to adapt to the new host, whereas others do not. If adaptation is required, predicting whether cross-species transmission will occur requires knowledge of the genetic make-up of the circulating viruses and the changes required for a virus to adapt. Kim Pepin and colleagues describe on page 802 how this information can be acquired and analyse the literature to assess what relevant information is normally captured in studies on four sample viruses.
