Nevertheless, they identified new proteins not previously associated and expressed at significantly higher levels in subjects with severe COVID-19, among which were a group of growth factors and associated proteins that included growth factor 5 (FGF-5), colony stimulating factor (CSF), ephrin type-A (EPHA2), transforming growth factor alpha (TGF-α), and beta-nerve growth factor (β-NGF). Here, CSF2 is linked to COVID-19.