A 50-year-old woman in Vietnam developed a rare and deadly fungal infection called mucormycosis while recovering from dengue fever. She had weakened immunity from taking steroids for other conditions and from the dengue virus itself. The infection caused black, dead tissue to rapidly spread in her nose and around her eye. Despite treatment with antifungal medications, the infection progressed, and she died within days. The case shows how important it is to watch for dangerous opportunistic infections in dengue patients, especially those already dealing with weakened immune systems.