One particular signature is the so-called type 1 interferon response in people with active MS and SLE.99 A proportion of patients with MS have a type 1 interferon response detectable in their peripheral blood transcriptome,100 which predicts poor treatment response to interferon-beta.101-104 As this response typically occurs in response to viral infections, these observations raise the question of whether or not the peripheral type 1 interferon response in untreated patients with active MS is a biomarker of EBV lytic infection. Here, IFNB1 is linked to myeloid sarcoma.