In an update on Oropouche virus yesterday, the Pan American Health Organization (PAHO) said Brazilian scientists are investigating miscarriages in two pregnant women infected by the insect-borne virus this year and the possibility of other poor fetal outcomes, including microcephaly.
Oropouche virus, which causes symptoms similar to dengue, is most commonly spread by a species of biting midge called Culicoides paraensis but can also be transmitted by certain Culex mosquitoes. Over the past several months, the virus has spread to areas or countries where locally acquired cases hadn't been reported before, and, as of July 16, nearly 7,700 cases had been reported in five countries in the Americas this year, with Brazil bearing the biggest burden.
Two recent miscarriages
On July 12, Brazilian officials reported an infection in a pregnant woman who contracted the virus in Pernambuco state and experienced a miscarriage at 30 weeks gestation. Fetal samples examined at the Evandro Chagas Institute confirmed Oropouche virus in umbilical cord blood and fetal tissues, suggesting vertical transmission. Final classification of the case is pending further investigation.
Officials also reported a second suspected case involving a pregnant woman from the same state who had been sick with Oropouche virus symptoms and who miscarried in the eighth week of gestation. Polymerase chain reaction testing on a serum sample collected on June 12 was positive for Oropouche virus and negative for Zika, chikungunya, dengue, and Mayoro viruses. Researchers weren't able to collect fetal samples for testing.
Earlier investigations hint at similar findings
Retrospective testing of blood samples collected for arbovirus research found four newborns with microcephaly who had antibodies against Oropouche virus but were negative for other viruses.
"The limitations of the studies do not allow establishing a causal relationship between [Oropouche virus] infection and neurological malformations," PAHO said. It also referenced a 1982 report from Brazilian scientists who were investigating the country's first outbreak involving the virus. Of nine Oropouche virus infections in pregnant women diagnosed using serological tests at the time, two experienced miscarriages in the second month of gestation.
PAHO said though the vertical transmission and consequences in newborns are still under investigation, it wanted member states to be aware and to intensify surveillance in pregnant women.
