Yellow Fever Hepatitis: Rediscovering Villela Bodies, a Neglected Histopathologic Clue

To the Editor.—In 2024, Brazil experienced the largest and most severe dengue epidemic of the 21st century, with numerous cases and high mortality rates, more than 10 years after the emergence of chikungunya and Zika in Brazil. In addition, oropouche fever spread to areas outside of the Amazon region, and now, in early 2025, there is an ongoing yellow fever (YF) outbreak in the state of São Paulo, in southeastern Brazil, so far mostly affecting nonhuman primates.1Among arboviruses, YF is the prototype viral hemorrhagic fever, with a mortality rate of approximately 35%. YF is endemic to sub-Saharan Africa and South America, particularly the Amazon River basin. In Brazil, urban transmission of YF has not occurred since 1942, but every 7 to 10 years, new epizootics and outbreaks arise in areas where forest and city meet, affecting susceptible, unvaccinated individuals. Data from the São Paulo State Health Department show 696 YF cases reported in São Paulo between 2017 and 2019, with 232 deaths (33.3%). In 2020 and 2021, one case was reported each year, with no deaths. In 2022 and 2023, 2 cases were reported each year, with a case fatality rate of 50%.1Throughout medical history, autopsies have been a powerful tool for elucidating the etiology and pathogenesis of infectious diseases, playing a crucial role in the COVID-19 and mpox epidemics. During the YF epidemic, our autopsy service conducted 85 autopsies on suspected or confirmed cases of severe YF.2,3 The goal of these autopsies was to determine the cause of death in cases with atypical presentation; clarify lethal outcomes in liver transplant recipients; and diagnose YF vaccine–associated viscerotropic disease (commonly abbreviated as “YEL-AVD”), based on the Brighton criteria.2,3The pathology of YF has been extensively documented in autopsy studies from the late 19th and early 20th centuries. Liver pathology has remained a central focus, notably in the studies of Councilman4 and Rocha-Lima,5 who described the characteristic mid-zonal hepatitis with eosinophilic corpuscles (Councilman bodies).4,5 Torres6 and Cowdry and Kitchen7 later described nuclear inclusions in YF liver tissue, more clearly observed in primates. These inclusions exhibited various morphologic features, with diseased hepatocytes showing prominent nucleoli at the margins of steatotic and apoptotic degeneration, although YF virus virions are not present in these inclusions, as determined by electron microscopy.6,7A distinctive histopathologic feature of the liver in YF is the presence of “ochre bodies” in hematoxylin-eosin–stained sections, located in the cytoplasm of hepatocytes and Kupffer cells, observed within Councilman bodies themselves, or seen as cell-free material in the lobular interstitium and hepatic sinusoids. These ochre bodies were described in an article published in the Archives of Pathology in 1941 by the Brazilian pathologist Eudoro Libânio Villela, and were found in YF late-stage cases, occurring after the 8th to 10th day of symptom onset.8 Later named Villela bodies (VBs), alongside Councilman bodies, these have become recognized as key features of YF histopathology.9From the 1990s onward, VBs were rarely cited.9 However, revisiting the work of Villela, we have linked a granular pattern of positivity for YF Envelope antigen in immunohistochemical reactions to VBs.2,3,9 Initially interpreted as hemosiderin or bile pigments, VBs do not stain with Prussian blue (for hemosiderin) or Hall stain (for bilirubin) and exhibit specific staining properties, such as orange-ochre in Sudan III dye, black in Del Río Hortega and Fontana-Masson stains, and fuchsia in Ziehl-Neelsen stain.8 The Figure (A through E) shows VBs stained with hematoxylin-eosin and fuchsin, along with their ultrastructure.Villela bodies are thought to represent a ceroid pigment resulting from lipid peroxidation in lysosomes, potentially containing YF virus antigenic fragments. In our autopsies—often from cases with extended evolution due to state-of-the-art care provided by our institution—VBs were frequently observed.2,3,9 Although liver biopsy is contraindicated in the acute phase of hemorrhagic fever, rare reports also describe VBs in liver biopsy specimens from YF cases.9 It remains to be seen whether VBs appear with other arboviruses, such as dengue virus.Villela bodies have a similar histologic appearance and histochemical affinity to ceroid pigment found in the liver in other diseases. However, their distribution in liver tissue is an important diagnostic clue. In YF, the ceroid pigmentation of VBs is found within hepatocytes, Kupffer cells, within Councilman bodies, and as cell-free material in the interstitium, mainly in hepatic zones 2 and 3 (Figure, A through E). This is different from the distribution of ceroid pigment found in other diseases, such as within perivenular hepatocytes of elderly people as part of the normal aging process, or within scattered hepatocytes in the liver parenchyma in patients with Dubin-Johnson, Gilbert, and telomere-shortening syndromes, or in patients with long-term phenobarbital use. Ceroid pigment may also be found in Kupffer cells, to varying degrees, near foci of chronic inflammatory reaction in chronic viral hepatitis, resolving hepatitis, drug-induced liver injury, acute fatty liver of pregnancy, and steatohepatitis.10With the emergence and re-emergence of arboviral diseases in Brazil and the Americas, understanding the histopathology of tissue lesions caused by these agents is crucial. The timely and accurate identification and reporting of findings across varied clinical presentations places diagnostic pathology at the forefront of epidemic preparedness. Autopsy plays a central role in this, not only in diagnosis but also in uncovering mechanisms of pathogenesis, as seen during the COVID-19 pandemic and mpox epidemic. Integrating clinical and epidemiologic data with macroscopic and histologic analyses is vital, combining accessible histochemical stains with advanced techniques like multiplex immunohistochemistry and transcriptomics. The rediscovery of findings such as VBs highlights autopsy’s enduring value in understanding arboviral diseases and addressing global health challenges.2,3,9The authors wish to thank all health workers who provided care to patients with severe yellow fever, to the Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (FMUSP)–Yellow Fever Crisis Committee, and to all medical residents, technicians, and professors from the Pathology Department - FMUSP who participated in the autopsy procedures.