AMAZON REGION — Brazil recorded over 30,000 officially recorded cases of the Oropouche virus and its first confirmed death during the 2023 outbreak. The virus spread to all Brazilian states during that period, leading the World Health Organization to express concern and call for accelerated development of prevention and control tools.

Research indicates the Oropouche virus has infected approximately 9.4 million people in Latin America and the Caribbean since 1960, with around 5.5 million cases occurring in Brazil. In Manaus, an estimated 300,000 people were infected between 2023 and 2024. The prevalence of antibodies against the virus in Manaus increased from 11.4 percent in November 2023 to 25.7 percent in November 2024.

José Luiz Proença Módena, a coordinator at the State University of Campinas, stated, "We are facing a disease of much greater magnitude than previously imagined, which requires greater attention. We estimate that one in every thousand diagnosed cases progresses to serious complications such as neurological disorders, microcephaly, miscarriages, and liver complications, raising the priority level for public health." The Oropouche virus can cause fever and symptoms similar to dengue, and in some cases, it can lead to neurological complications such as meningitis and meningoencephalitis. It can also cause microcephaly through mother-to-fetus transmission.

Individuals infected with the Oropouche virus in the 1980s can still neutralize the recent viral strain. "Although long-term immunity appears to exist for those who have already been infected, the speed with which the virus has spread across all Brazilian states shows that the healthcare system needs new detection systems, including those focused on surveillance far from major urban centers," Módena said.

The Oropouche virus is transmitted by the gunpowder midge, scientifically known as Culicoides paraensis. Cases of the virus are 11 times more prevalent in rural areas compared to urban areas. High temperatures and rainfall contribute to the spread of the gunpowder midge. The midge is three times smaller than a common mosquito, allowing it to pass through standard mosquito nets. Brazil's Southeast region accounted for 57.9 percent of reported cases. The state of Espírito Santo recorded the highest cumulative rate in Brazil, with 318 cases per 100,000 people.

Researchers identified a new Oropouche virus lineage resulting from genetic reassortment, a process where two different viruses infect the same cell. This genetic change increases the virus's replication capacity and makes it harder for antibodies from previous infections to neutralize it.

No independent assessment was available for this report.