TNF and Middle East respiratory syndrome: Patients with severe COVID-19 have higher serum levels of pro-inflammatory cytokines (TNF-α, IL-1, and IL-6) and chemokines (IL-8) compared to individuals with mild disease or healthy controls, and similar levels compared to patients with Severe Acute Respitatory Syndrome (SARS) or Middle East Respiratory Syndrome (MERS) [2].