Detection of a Human Adenovirus Outbreak, Including Some Critical Infections, Using Multi-Pathogen Testing at a Large University, September 2022—January 2023

Abstract Background Human adenoviruses (HAdV) can cause outbreaks of flu-like illness in university settings. Most infections in healthy young adults are mild; severe illnesses rarely occur. In Fall 2022, an adenovirus outbreak was identified in university students. Methods HAdV cases were defined as university students 17 to 26 years-old who presented to University Health Service or nearby emergency department with flu-like symptoms (e.g., fever, cough, headache, myalgia, nausea) and were confirmed adenovirus infections by polymerase chain reaction (PCR). Demographic and clinical characteristics were abstracted from electronic medical records, clinical severity was categorized as mild, moderate, severe, or critical. We performed contact investigations among critical cases. A subset of specimens was sequenced to confirm the HAdV type. Results From September 28, 2022, to January 30, 2023, 90 PCR-confirmed cases were identified (51% female; mean age=19.6 years). Most cases (88.9%) had mild illness. Seven cases required hospitalization, including two critical cases that required intensive care. Contact investigation identified 44 close contacts; 6 (14%) were confirmed HAdV cases and 8 (18%) reported symptoms but never sought care. All typed HAdV-positive specimens (n=36) were type 4. Conclusions While most students with confirmed HAdV had mild illness, seven otherwise healthy students had severe or critical illness. Between the relatively high number of hospitalizations and proportion of close contacts with symptoms who did not seek care, the true number of HAdV cases was likely higher. Our findings illustrate the need to consider a wide range of pathogens, even when other viruses are known to be circulating.