Following publication of the article, the authors noticed two small errors introduced during the typesetting process of the article. Firstly, figures were inadvertently published in black/white, rather than in colour. Secondly, a label within Figure 3 was adjusted in error during the typesetting process; the upper-scale label in Figure 3a, for EBV DNA, should have read “≥4000 copies/mL”, not “4000 copies/mL”. The figure has been corrected.