The association of the number of secondary bacterial infections with death remained significant upon adjustment to age, minimal blood oxygen saturation, maximal CRP and minimal albumin levels, all variables of disease severity, in COVID-19 (one infection 2.48-fold (1.16–5.29), p = 0.019; more than one infection 7.64-fold (2.46–27), P < 0.001), but not in the infected influenza patients (one infection 1.11-fold (0.38–2.92), p = 0.8; more than one infection 1.21-fold (0.22–5.51), P = 0.8) (Fig. 1). Here, CRP is linked to bacterial infectious disease.