Phylogeographic patterns of the yellow fever virus around the metropolitan region of São Paulo, Brazil, 2016-2019.

From 2016 to 2019, the largest outbreak caused by the Yellow Fever virus (YFV) in the 21st century in the Americas occurred in southeastern Brazil. A sylvatic cycle of transmission was reported near densely populated areas, such as the large metropolitan area of the city of São Paulo. Here, we describe the origin, spread, and movement of the YFV throughout the state of São Paulo. Whole-genome sequences were obtained from tissues of two patients who died due to severe yellow fever, during 2018-2019. Molecular analysis indicated that all analyzed tissues were positive for YFV RNA, with the liver being the organ with the highest amount of viral RNA. Sequence analysis indicates that genomes belonged to the South American genotype I and were grouped in the epidemic clade II, which includes sequences from the states of Goiás, Minas Gerais, and São Paulo of previous years. The analysis of viral dispersion indicates that the outbreak originated in Goiás at the end of 2014 and reached the state of São Paulo through the state of Minas Gerais after 2016. When the virus reached near the urban area, it spread towards both the east and south regions of the state, not establishing an urban transmission cycle in the metropolitan region of São Paulo. The virus that moved towards the east met with YFV coming from the south of the state of Rio de Janeiro, and the YFV that was carried to the south reached the Brazilian states located in the south region of the country.

Origin of the São Paulo Yellow Fever epidemic of 2017-2018 revealed through molecular epidemiological analysis of fatal cases.

The largest outbreak of yellow fever of the 21st century in the Americas began in 2016, with intense circulation in the southeastern states of Brazil, particularly in sylvatic environments near densely populated areas including the metropolitan region of São Paulo city (MRSP) during 2017-2018. Herein, we describe the origin and molecular epidemiology of yellow fever virus (YFV) during this outbreak inferred from 36 full genome sequences taken from individuals who died following infection with zoonotic YFV. Our analysis revealed that these deaths were due to three genetic variants of sylvatic YFV that belong the South American I genotype and that were related to viruses previously isolated in 2017 from other locations in Brazil (Minas Gerais, Espírito Santo, Bahia and Rio de Janeiro states). Each variant represented an independent virus introduction into the MRSP. Phylogeographic and geopositioning analyses suggested that the virus moved around the peri-urban area without detectable human-to-human transmission, and towards the Atlantic rain forest causing human spill-over in nearby cities, yet in the absence of sustained viral transmission in the urban environment.

Zika and chikungunya virus infections in hematopoietic stem cell transplant recipients and oncohematological patients.

Aedes mosquitoes are well adapted in domestic environments and widespread in tropical regions. Since 2015, Brazil has been experiencing a triple epidemic of dengue (DENV), chikungunya (CHKV), and Zika (ZIKV) viruses. The last 2 viruses are likely following the path of DENV, which has been endemic in most parts of the country since the 1980s. Given this triple epidemic, we proposed a prospective and collaborative study to assess the prevalence, morbidity, and mortality of DENV, CHKV, and ZIKV infections in hematopoietic stem cell transplant (HSCT) recipients and oncohematological patients. A case definition strategy (fever and rash) was used to prompt diagnostic investigation of DENV, ZIKV, and CHKV, which was accomplished by real-time polymerase chain reaction with plasma and urine samples. Clinical follow-up was performed 7 and 30 days after symptom onset. We report here the first cases of ZIKV and CHKV infections diagnosed in this ongoing study. From February to May 2016, 9 of the 26 patients (34.6%) fulfilling case definition criteria were diagnosed with DENV (3 cases), ZIKV (4 cases), or CHKV (2 cases) infections. Prolonged viremia and viruria were observed in dengue and Zika fever cases, respectively. Thrombocytopenia was the most frequent complication. Delayed engraftment was noted in 1 patient who acquired ZIKV 25 days before HSCT. All patients survived without sequelae. With the geographic expansion of arboviruses, donor and recipient screening may become mandatory. Patients living in areas where these viruses are not endemic are also at risk, since these viruses can be transmitted by blood as well as organ or tissue transplantation.