This contrasted with DENV, where only IL-6 exhibited a strong correlation with [18F]FDG PET signals in the spleen (ρ = 0.72; CI: 0.38–0.89; p = 0.0007), despite IL-6 and TNF-α having more exaggerated expression in DENV spleens relative to ZIKV (8–14-fold higher than pre-infection) (Fig. 4b,c). Here, IL6 is linked to infection.