Yellow fever is a public health challenge due to its high case fatality, early clinical presentation that can be easily confused with other arboviruses, and epidemic potential, especially with expansion of vectors into urban centers such as São Paulo. Investigating its behavior is essential to better understand determinants of the disease and improve prevention, surveillance, and rapid response strategies. This study aimed to characterize the demographic, clinical, epidemiological, and laboratory profile of confirmed yellow fever cases in the municipality of São Paulo between 2017 and 2025. Ecological study using data obtained from SINAN, covering January 2017 to April 2025. Variables analyzed included demographic (sex, age, race, education), clinical (symptoms; intervals between symptom onset, hospitalization, and death), epidemiological (vaccination status, occurrence of autochthonous cases, presence of vectors, epizootics), and laboratory (IgM and RT-PCR results; biochemical tests such as bilirubin and transaminases). Statistical analysis used Microsoft Excel Version 2505 and Power Query to calculate means, percentages, and standard deviations. A total of 309 confirmed cases were identified. Most were male (80%), with mean age of 43 years, predominantly White (57%) and with completed high school (18.1%). Frequent symptoms included abdominal pain (52.1%), oliguria (31.1%), hemorrhagic signs (23.3%), and Faget sign (12.9%). Hospitalization rate was 91.3%, with mean of 4.8 days between symptom onset and hospitalization. Case fatality rate was 32.7%, with mean of 9.8 days between symptom onset and death. Vaccination coverage among cases was 16%. Diagnosis showed marked liver injury: AST and ALT were substantially elevated (mean 5,667 and 3,679 U/L), as were total and direct bilirubin (mean 3.7 and 3.0 mg/dL). Yellow fever remains a challenge in São Paulo, with low vaccination coverage, rapid progression, and high case fatality. High frequency of severe symptoms and delays in hospitalization reinforce the need for professional training for early diagnosis. There is urgency to expand vaccine coverage, reduce time to diagnosis, and improve record quality to support public health responses and prevent new urban outbreaks.
Silva et al. (Sun,) studied this question.