The management of patients with acute severe ulcerative colitis and SARS-CoV-2 presents a clinical challenge. We report on the first case of a patient with acute severe ulcerative colitis and mild coronavirus disease 2019 (COVID-19) who received rescue infliximab therapy, followed by a relapse caused by enterohemorrhagic Escherichia coli 0157:H7. The treatment challenges we faced were biologic therapy administration during active COVID-19, about which little was known at the time, and how to treat EHEC due to the risk of hemolytic uremic syndrome. Acute severe ulcerative colitis was treated with rescue infliximab therapy, and enteric infection with an antibiotic, both with satisfactory clinical response. The decision to induce biologic therapy for inflammatory bowel disease relapse in SARS-CoV-2-positive patients should be made on a case-to-case basis and should be driven by the dominant disease. Our patient tested positive for SARS-CoV-2, but actually had mild disease. At the same time, she had acute severe ulcerative colitis, so we started anti-tumor necrosis factor therapy despite serological tests and the recommendation to delay biological therapy administration for two-weeks. Second, due to severity of the first flare, COVID-19, and the patient's general condition, we opted for an antibiotic treatment of Escherichia coli 0157:H7 while monitoring the parameters of potential hemolytic uremic syndrome development.