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2023-2024 Oropouche virus disease outbreak

HAL333/sandbox3
Micrograph of Marburg viruses
Disease	A biting midge, a known vector for Oropouche fever
Date	December 2023 - ongoing
Confirmed cases	8000+
Deaths	2

An outbreak of Oropouche fever began in December 2023. Over 8000 infections have occurred, including the first outside its endemic Amazon region. As of August 16, two fatalities were reported. These are the first known deaths caused by the disease. Brazil, Bolivia, Peru, Colombia and Cuba have reported cases. Cases among travelers to the region have been identified in the United States and Europe.

Virus and previous epidemiology

The causative agent of Oropouche fever, Oropouche orthobunyavirus, was first discovered in the Carribean nation Trinidad and Tobago. Five years later, it was first detected in Brazil via an infected sloth. Consequently, the disease is also known as "sloth fever". Sloths, in addition to some bird species and non-human primates, are known to serve as natural reservoirs for the virus.

Since the 1960s, periodical outbreaks have occured, albeit only in the Amazon region.

Unlike the mosquito-borne dengue or zika, the Oropouche virus is transmitted by a biting midge, specifically Culicoides paraensis. C. paraensis is also found throughout the United States. Although no other vector has been demonstrated, the virus has been identified in insects such as the Culex quinquefasciatus mosquito.

Historically, the disease results in mild symptoms: fever, headache, nausea, vomiting, and muscle, joint, or eye pain. Some cases may result in severe neurological damage. No vaccines or treatments exist.

Outbreak

According to the CDC, over 8000 Oropouche cases were identified from January 1 to August 1, 2024. Although most cases have occured in Brazil, cases have also been reported in Bolivia, Peru, Colombia, and Cuba. The Cuban infections mark the first Oropouche cases beyond the Amazon. As of August 16, two fatalities were reported. These are the first known deaths caused by the disease. In early August 2024, the Pan American Health Organization updated the diseases's risk level from moderate to high.

On August 16, the U.S. Centers for Disease Control and Prevention issued a health alert for the region. It reported that 21 American had contracted the virus after traveling to Cuba. Although three were hospitalized, no deaths were reported. Travel-associated cases have also occurred in Italy, Germany, and Spain.

Fetal transmission

Microcephaly, which severely harms brain development, has been indicated in some Oropouche infections.

Five Oropouche cases involved vertical transmission of the virus from pregnant patient to fetus. Brazil health authorities are investigating the possibility of fetal deaths and disabilities that the disease may have caused. In the state of Pará, the Evandro Chagas Institute identified antibodies against Oropouche in four newborns with microcephaly: a birth defect characterized by an abnormally small head. However, a causal relationship has not been confirmed.

Viruses closely related to Oropouche——such as Akabane virus——are known to induce congenital defects or stillborns in livestock.

Causes

Climate change, deforestation, and urbanization have been suggested as possible contributing factors to the outbreak.