Oropouche virus (OROV), colloquially known as “sloth fever,” has emerged as a significant public health concern, particularly for travelers to endemic regions. Transmitted primarily through the bites of infected biting midges (Culicoides paraensis) and certain mosquito species, OROV has been responsible for numerous outbreaks in South and Central America, with recent cases reported in Europe and the United States.
Epidemiology and Transmission
Since its initial identification in Trinidad and Tobago in 1955, OROV has caused over 30 epidemics, affecting more than half a million individuals in countries such as Brazil, Peru, and Panama. The virus maintains a sylvatic cycle involving sloths, non-human primates, and birds as natural reservoirs. Human infections occur when vectors like biting midges transmit the virus from these reservoirs. Notably, the Culicoides paraensis midge is prevalent in many regions, facilitating rapid virus transmission.
Clinical Manifestations
The incubation period for OROV ranges from 4 to 8 days post-exposure. Symptoms typically present abruptly and can include:
- Fever: Almost universally observed in infected individuals.
- Severe Headache: Reported in approximately 70–80% of cases.
- Myalgia and Arthralgia: Muscle and joint pains are prevalent.
- Chills, Nausea, and Vomiting: These symptoms are also associated with the disease.
- Photophobia: Sensitivity to light.
- Rash: A skin rash may develop in some cases.
While most individuals recover within 2 to 7 days, complications can arise. Severe cases may involve neurological manifestations such as meningitis or encephalitis, potentially leading to fatalities. Notably, the first recorded deaths attributed to OROV occurred in Brazil in 2024.
Recent Outbreaks and Geographic Spread
The 2023–2024 outbreak marked a significant escalation in OROV activity. Over 9,852 infections were reported, with cases extending beyond the Amazon region. Local transmission was documented in Bolivia, Peru, Colombia, and notably, Cuba, marking the virus’s first appearance outside the Amazon. Travel-associated cases emerged in the United States and Europe, indicating the virus’s expanding reach. As of August 2024, two fatalities were reported, underscoring the virus’s potential severity.
Risk to Travelers
Travelers to endemic areas face a tangible risk of OROV infection. The U.S. Centers for Disease Control and Prevention (CDC) reported 21 cases among Americans returning from Cuba, with three hospitalizations but no fatalities. Similarly, cases have been identified in European travelers, including those from Italy, Germany, and Spain. Given the widespread presence of the Culicoides paraensis midge, the potential for local transmission in non-endemic regions exists, though it remains low.
Preventive Measures
Currently, no vaccine exists for OROV, and treatment is primarily supportive. Prevention focuses on minimizing exposure to vector bites:
- Personal Protective Measures: Wearing clothing that covers the arms and legs, and applying insect repellents containing DEET or icaridin can reduce the risk of bites.
- Use of Fine-Mesh Nets: Standard bed nets are less effective against biting midges due to their small size. Employing fine-mesh nets over sleeping areas and ensuring window and door screens are intact can offer better protection.
- Vector Control: Reducing midge populations through environmental management, such as eliminating breeding sites, and using chemical insecticides as residual sprays on premises can help control the spread.
Special Considerations for Pregnant Travelers
Pregnant individuals should exercise heightened caution. There is evidence of vertical transmission of OROV, with reported cases of infection during pregnancy associated with adverse outcomes, including pregnancy loss and congenital anomalies. Consequently, pregnant travelers are advised to avoid non-essential travel to high transmission and endemic areas or to implement stringent personal protective strategies if travel is unavoidable.
Conclusion
The resurgence and geographic expansion of OROV, or “sloth fever,” necessitate increased awareness among travelers and healthcare professionals. Understanding the modes of transmission, recognizing symptoms, and implementing preventive measures are crucial steps in mitigating the risk of infection. As the global landscape of vector-borne diseases evolves, staying informed and vigilant remains paramount.
