We’re hearing a lot more about viral vectors and vaccine applications with the growing trend in regenerative medicine, so this is an area we’ll be doing more dedicated research on in the near future. However in general the principles of membrane and MWCO selection are the same as with proteins and other biomolecules, unless there are specific considerations for your virus. The rule of thumb is to choose a molecular weight cut off (MWCO) close to one third the molecular weight of your target. In the case of viruses where molecular weight is not as relevant as diameter there is a comparison chart which gives the best MWCO for diameter and DNA length. For Lentivirus for example which has a ~90nm diameter we find that 300K MWCO membranes work optimally, with 100K MWCOs also giving good results at the sacrifice of speed.
The below link provides a review of ultrafiltration protocols for virus concentration and purification.
https://promotions.sartorius.com/fileadmin/media/activities/vivaflow/Appl_Guide_Concentration-Purification-Viruses_SL-4002-e.pdf