We previously reported that upon EBV infection, B cells undergo a transient period of hyper-proliferation during which a cell can divide up to four times in 1 day.21 This increased division rate requires that infected cells replicate their genomes very rapidly, potentially leading to DNA replicative stress and activation of the ATR/Chk1 signaling pathway. The gene discussed is CHEK1; the disease is Epstein-Barr virus infection.