Severe Pneumonia Due to Streptococcal Toxic Shock Syndrome in a Patient Positive for Influenza Virus Antigen: A Case Report.

Since the onset of the COVID-19 pandemic, the incidence of streptococcal toxic shock syndrome (STSS) has increased. Additionally, complications involving influenza virus infections in STSS cases have been reported more frequently than in the pre-pandemic period. We report the case of a 69-year-old man who presented to the ED with progressive dyspnea and fever, without any signs suggestive of soft tissue infection. Chest CT revealed right-sided pneumonia, and a rapid influenza test returned positive. On the second day of hospitalization, Streptococcus pyogenes (emm1) was isolated from both blood and sputum cultures. Despite aggressive intensive care, including fluid resuscitation, vasoactive support, mechanical ventilation, and renal replacement therapy, the patient's condition deteriorated rapidly. He died 24 hours after admission to the ICU. STSS is a rapidly progressing disease with a high mortality rate, capable of causing severe clinical decline within a short time. Clinicians should remain vigilant for the rising occurrence of STSS and influenza coinfections during the COVID-19 era to improve differential diagnosis and optimize early treatment strategies.