Pulmonary Complications in Fatal Yellow Fever, Brazil, 2017–2019

Yellow fever (YF) mainly causes severe hepatitis; data on pulmonary pathology remain limited. We investigated respiratory tract pathology in 73 fatal YF cases during the 2017-2019 epidemic in São Paulo, Brazil. All patients died from YF-related fulminant hepatitis. Autopsies revealed frequent tracheitis (91%), pulmonary edema and hemorrhage (100%), diffuse alveolar damage (84%), secondary pneumonia (84%), and bronchoaspiration (60%). Microabscesses, thrombi, and hemophagocytosis were also observed. In 5 cases of vaccine-associated viscerotropic disease, hemorrhage and diffuse alveolar damage were prominent. We detected antigens of YF virus in all cases and viral RNA in 94%. Molecular analysis identified bacterial and fungal pathogens in pneumonia, including gram-negative bacilli, Candida spp., and Aspergillus spp. Electron microscopy did not reveal viral particles in 3 examined cases. Our findings underscore the respiratory tract involvement in severe YF and could help guide diagnosis, intensive care, and public health preparedness in future outbreaks.