Fiocruz contributes to study on vertical transmission of Oropouche

A study published in the New England Journal of Medicine confirms the vertical transmission of the Oropouche virus in a case of fetal death recorded in Ceará. This is the third confirmed case in the country. Vertical transmission occurs when a microorganism passes from mother to baby during pregnancy. The work was carried out in collaboration with the Oswaldo Cruz Institute (IOC/Fiocruz), through the Laboratory of Arboviruses and Hemorrhagic Viruses, which acts as a regional reference in arboviruses for the Brazilian Ministry of Health.

Vertical transmission was detected by the surveillance service of the Ceará Health Department (Sesa/CE). The following collaborated with the study: SESA/CE; University of Fortaleza (Unifor); Federal University of Ceará (UFC); Ceará Death Verification Service Dr. Rocha Furtado (SVO/Sesa/CE); Central Public Health Laboratory of Ceará (Lacen-CE); IOC/Fiocruz; São Leopoldo Mandic College; and Paulo Marcelo Martins Rodrigues School of Public Health of Ceará (ESP/CE).

According to the Ministry of Health, Brazil recorded 8,200 cases of Oropouche fever in 2024. In a bulletin with data up to October 19th, the Ministry reported two confirmed cases of vertical transmission and more than 20 under investigation. The two confirmed records correspond to a case of fetal death in Pernambuco and a case of congenital anomalies in Acre.

Viral strain

The study provides information on the clinical condition of the pregnant woman, who began to show symptoms compatible with Oropouche, such as fever and body and headaches, on July 24th, during the 30th week of pregnancy. Fetal death was diagnosed on August 5th. With the family's permission, the specialists carried out minimally invasive procedures to take samples from the baby.

At Lacen-CE, the Oropouche virus was detected in several fetal samples, including cerebrospinal fluid and brain, lung and liver tissue, as well as the umbilical cord and placenta. Infection with the pathogen was also confirmed in the mother's blood sample.

As a reference laboratory, the IOC/Fiocruz Laboratory of Arboviruses and Hemorrhagic Viruses received samples for a new battery of tests. After confirming the positive result, genetic sequencing of the virus detected in the fetus was carried out. The analysis pointed to the presence of the lineage called OROVBR_2015-2024, which recently emerged in Brazil and was characterized in an article published in the scientific journal Nature Medicine led by IOC/Fiocruz and the Leônidas e Maria Deane Institute (Fiocruz Amazônia).

“The analysis of these genomes showed that the virus belongs to the strain that emerged in the Northern Region, spread through Brazil and reached different countries such as Bolivia, Cuba, the United States and Italy,” points out virologist Felipe Naveca, head of the Laboratory of Arboviruses and Hemorrhagic Viruses at IOC/Fiocruz. ”This is yet another study that shows that the Oropouche virus is capable of vertical infection. The mechanism by which this happens is still unknown, but there is already robust evidence that Oropouche can cause severe damage to fetuses, including death," the researcher adds.