What is the % of malignancies that are from viruses now, as more are being discovered each year?

Hard to know: We know of a few cancers caused by viruses such as cervical cancer and head and neck cancer. These are the most widely discussed. There are other more rare cancers such as a t cell lymphoma associated with an htlv infection and then there are still other cancers such as hepatocellular carcinoma that aren't caused but are associated with an infection such as hepatitis c.