PAHO urges more surveillance for chikungunya, oropouche cases in Americas

The Pan American Health Organization (PAHO) has called for reinforcing surveillance, clinical management and vector control to address localized chikungunya outbreaks and the ongoing circulation of the Oropouche virus (OROV) in countries across the Americas.

The simultaneous presence of these and other arboviruses increases the risk of outbreaks, severe complications, and fatalities among vulnerable populations.

According to a new epidemiological alert from PAHO, the largest chikungunya outbreaks in 2025 have been concentrated in South America—particularly in Bolivia, Brazil, and Paraguay—and in parts of the Caribbean.

These are associated with the Asian and East/Central/South African (ECSA) genotypes, marking a shift in the pattern observed since 2014. Cases reported in the Indian Ocean region, Europe, and Asia also raise the risk of reintroduction and further spread into new areas with conditions conducive to transmission.

As of August 9, 2025, 14 countries in the region reported a total of 212,029 suspected chikungunya cases and 110 deaths, with more than 97% occurring in South America. In comparison, 2024 saw 431,417 reported cases and 245 deaths—indicating a decline this year, though localized outbreaks remain active.

Meanwhile, in the first seven months of 2025, over 12,700 confirmed Oropouche cases have been reported in 11 countries, including autochthonous cases in Brazil, Colombia, Cuba, Panama, Peru, and Venezuela.

Globally, chikungunya has circulated for decades in Africa, Asia, and the Indian subcontinent. It was first detected in Europe (Italy) in 2007 and arrived in the Americas in 2013. Until mid-August 2025, more than 270,000 cases had been recorded across Africa, Europe, Southeast Asia, and the Western Pacific, with outbreaks in Senegal, France, India, and China. On Réunion Island, the 2024 outbreak has resulted in over 47,500 confirmed cases.

Regionally, the Asian genotype predominated between 2014 and 2017. However, the presence of the ECSA genotype in at least four countries is concerning, as its cocirculation with the Asian type could enhance viral adaptation. “Understanding chikungunya’s genetic lineages is essential to predict transmission dynamics and tailor public health responses,” PAHO noted.

Chikungunya follows a seasonal pattern: cases in the Southern Hemisphere typically rise in the first half of the year during the rainy season, while in Central America, Mexico, and the Caribbean, they usually increase in the second half. In 2025, however, those regions have contributed minimally so far.

Traditionally, Oropouche transmission was mostly confined to parts of the Amazon; yet in 2024 and 2025, its spread has extended to previously unaffected areas, highlighting the need to bolster surveillance, particularly through the integration of spatial and temporal analysis and leveraging geospatial tools to detect shifts in vector and case distribution.

Chikungunya is a viral disease primarily transmitted by the Aedes aegypti mosquito. Symptoms include high fever, rash, and intense muscle and joint pain, which can persist for months or even years, causing long-term disability. Severe cases may progress to shock, meningoencephalitis, or Guillain–Barré syndrome. Young children, older adults, pregnant individuals, and persons with underlying health conditions are most at risk. There is no specific treatment, so prevention focuses on avoiding mosquito bites.

Oropouche virus is mainly transmitted by the midge Culicoides paraensis, though the mosquito Culex quinquefasciatus may also play a role. It causes fever, headache, muscle aches, and sometimes neurological symptoms. There is no vaccine or specific antiviral treatment for this virus; care is symptomatic.

PAHO recommends enhancing early case detection and eliminating mosquito breeding sites in high-risk locations such as schools and health facilities. It also advises improving diagnosis using molecular methods like PCR—especially within the first five days of symptoms—and training healthcare workers in managing both acute and chronic cases.

For Oropouche, clinicians should include it in the differential diagnosis of dengue during the first week of symptoms and be alert to possible neurological complications like meningitis and encephalitis in later stages. Up to 60% of patients may experience relapses. Thus, ongoing monitoring and investigation of fatal cases are urged.

Community engagement is essential for reducing mosquito populations. Promoting the use of repellents and window screens, alongside multisectoral approaches, is crucial. Controlling Culicoides paraensis also calls for specific measures, such as draining temporary water bodies, removing stagnant pools, and clearing vegetation around homes to reduce breeding and resting grounds for the vector. (PAHO-Pan American Health Organization press statement)