ERVW-1 and plasma cell myeloma: In order to determine if the rebounding viruses isolated during relapse of multiple myeloma (second and third rebounds, pink and green shaded area Fig 1A) had diverged from those isolated during the initial rebound, we next analysed env sequences from five time points, the first being prior to the second peak viraemia on day +515 and the last at day +958 (Fig 3).