August 27, 2024, 3:42 PM EDT — A once-overlooked disease transmitted by insect bites is now drawing global attention due to its alarming spread and deadly impact. Health authorities are increasingly concerned about the Oropouche virus, which has seen a significant surge in cases this year.
As of August 1, more than 8,000 cases of Oropouche virus have been reported, predominantly in South America. However, the virus is now spreading to regions previously untouched by it, with travel-related cases emerging in the United States and Europe.
The Pan American Health Organization (PAHO), a regional body of the World Health Organization, has issued an epidemiological alert, elevating the public health risk to “high” for the Americas. The organization emphasized the need for enhanced surveillance and deeper understanding of the virus, which, despite historically being mild, has shown potential for severe outcomes.
The U.S. Centers for Disease Control and Prevention (CDC) also issued a health advisory, urging healthcare providers and public health authorities to remain vigilant. The advisory specifically cautions pregnant women against traveling to affected areas. The CDC confirmed that at least 21 U.S. travelers returning from Cuba have tested positive for the virus.
Understanding Oropouche Virus
Discovered in 1955 in a village in Trinidad and Tobago, the Oropouche virus has led to around 500,000 recorded cases since its discovery. Yet, the disease remains poorly understood. The Lancet medical journal recently described it as a “mysterious threat,” highlighting the gaps in scientific knowledge about the virus.
Approximately 60% of those infected with the virus develop symptoms, which can mimic those of dengue or Zika, including sudden fever, chills, headaches, muscle pain, and joint stiffness. Additional symptoms may include eye pain, light sensitivity, nausea, vomiting, diarrhea, fatigue, and rash. In rare instances, the virus can invade the nervous system, leading to conditions such as meningitis and encephalitis.
Though Oropouche belongs to a different viral family than Zika, it shares similar concerns and unknowns, particularly its potential impact on pregnant women. “We don’t fully understand its life cycle or transmission, and it seems to affect pregnant individuals,” said Janet Hamilton, Executive Director of the Council of State and Territorial Epidemiologists. “This underscores the need for more research.”
Transmission and Spread
The Oropouche virus is primarily spread through insect bites, especially from biting midges—tiny flies—and certain mosquito species. It is endemic to the Amazon basin, particularly in forested regions where insects maintain a transmission cycle with hosts such as rodents, sloths, and birds, earning the virus the nickname “sloth fever.”
Human interaction with infected insects, driven by climate change and deforestation, increases the risk of spreading the virus to urban areas. The current outbreak is rapidly expanding in both known and new regions, with locally acquired cases reported in Bolivia, Brazil, Colombia, Cuba, and Peru. While there is no evidence of local transmission in the United States, cases have been reported among travelers returning from these regions.
According to Dr. Erin Staples, a medical epidemiologist with the CDC’s Division of Vector-Borne Diseases, the risk of sustained local transmission in the continental U.S. remains low. However, she noted that the risk is more uncertain in territories like Puerto Rico and the U.S. Virgin Islands, where ecological conditions may resemble those of Cuba.
Current Developments and Concerns
The geographical shift in the virus’s spread has led experts to suspect new vectors may be involved. “We need more information to better assess at-risk areas,” Staples said. “We’re still learning about this virus and will provide updates as they become available.”
This year marks the first time deaths have been attributed to Oropouche virus, and there is emerging evidence that it can be transmitted from a pregnant woman to her fetus, potentially leading to adverse birth outcomes. Brazil reported two fatalities in otherwise healthy young women, and a third fatal case in a middle-aged man is under investigation by PAHO.
Additionally, there have been at least five cases in pregnant individuals that resulted in fetal death or congenital abnormalities, including microcephaly, a rare birth defect characterized by an underdeveloped brain. Experts believe these severe outcomes could be linked to the increased circulation of the virus.
“As more people become infected, we may observe rare and severe symptoms or fatalities,” Staples said. “These are areas of active investigation by the CDC and its partners.”
Protection and Precaution
Currently, there is no vaccine or specific antiviral treatment for Oropouche virus. Laboratory testing can confirm cases, but such testing is not widely available, and more common viruses like dengue must often be ruled out first.
“This is a crucial time to prioritize mosquito bite prevention,” advised Hamilton. She recommended avoiding outdoor activities during dawn and dusk when mosquitoes are most active, wearing protective clothing, and using effective mosquito repellents.
The CDC has issued two travel advisories: one advising travelers to South America to take “usual precautions” and another urging those visiting Cuba to take “enhanced precautions” against insect bites and to seek medical attention if necessary. Pregnant women, in particular, are advised to reconsider nonessential travel to Cuba.