Berlin, 14 April 2025
Similar to dengue or Zika viruses, the Oropouche virus causes a fever and there are also indications that it can damage the unborn child during pregnancy. Researchers at Charité – Universitätsmedizin Berlin have now shown that the virus is much more widespread in Latin America than previously assumed. The study, published in the journal The Lancet Infectious Diseases*, also indicates that climatic conditions have a strong influence on the incidence of infection.
The Oropouche virus has been known in Latin America since the 1950s, but for decades only a few cases per year were officially reported in most countries. An international research team led by Prof Jan Felix Drexler, head of the Virus Epidemiology working group at Charité’s Institute of Virology, has now conducted a comprehensive study to investigate how widespread the pathogen actually is. ‘According to our data, the Oropouche virus is massively underdiagnosed in Latin America,’ explains the head of the study, who also conducts research at the German Centre for Infection Research (DZIF). ‘In some regions, at least one in ten people have been infected with the pathogen.’
More widespread than thought – but not yet well studied
Oropouche virus causes non-specific symptoms such as fever, chills, headaches and aching limbs, sometimes also nausea or skin rashes. For a long time, the disease was considered to be mostly mild and reports of more severe cases with meningitis were rare. For unknown reasons, the number of infections reported from Latin America and the Caribbean has skyrocketed to more than 20,000 cases since the end of 2023 and two deaths have been observed in young, healthy women. In addition, several cases have been described in which infection during pregnancy appears to have led to miscarriages or malformations of the unborn child.
‘We still know comparatively little about the virus,’ explains Jan Felix Drexler. ‘What consequences an infection can have, including on the unborn child, needs to be investigated further. It is not yet clear whether there are parallels to the Zika virus. Overall, however, damage to the unborn child appears to be less frequent than with Zika.’ There is no vaccination against the virus or specific treatment for Oropouche fever.
For the study, the research team analysed more than 9,400 blood samples from healthy and sick people collected between 2001 and 2022 in Bolivia, Brazil, Colombia, Costa Rica, Ecuador and Peru. Antibodies against the Oropouche virus were found in around 6 per cent of the samples across all regions – an indication of an infection with the pathogen. There were strong regional differences: In Costa Rica, an average of 2 per cent of samples showed antibodies against the pathogen, in Ecuador it was 5 per cent and in the Amazon regions more than 10 per cent. At high altitudes, people had experienced Oropouche fever less frequently than in the warmer lowlands. The comparison of blood samples from different years also indicated that the incidence of infection varies from year to year.
Study estimates Oropouche infection risk for all Latin American countries
But what drives the incidence of infection? To find out, the researchers used machine learning to analyse whether there is a correlation between Oropouche infections and a range of environmental and demographic factors. According to the analysis, climatic conditions such as rain and constant temperatures appear to have the greatest influence on the occurrence of the Oropouche virus. ‘We therefore assume that the current Oropouche outbreak has been fuelled by weather phenomena such as El Niño,’ explains Jan Felix Drexler. ‘However, we have not found any evidence of changes in the properties of the virus as an alternative explanation for the current high number of cases. I believe it is possible that the Oropouche virus will spread even further in the future as a result of climate change.’
Based on the findings, the research team estimated the risk of Oropouche infection for the whole of Latin America and visualised it on an overview map. ‘The main area of distribution of the Oropouche virus is the Amazon rainforest,’ summarises Jan Felix Drexler. ‘However, there is also a high risk of infection in parts of Central America and the Caribbean as well as in the south and on the coast of Brazil.’
Protection against infection on site
‘Alongside the dengue and chikungunya viruses, the Oropouche virus is probably the most common virus spread by insects in Latin America,’ emphasises Jan Felix Drexler. To protect yourself from infection, he advises people visiting the region to protect themselves from insect bites. ‘To protect against the Oropouche virus, but also against other tropical viruses such as dengue or Zika, it is advisable to wear long clothing and use insect repellents containing DEET or Icaridin,’ says the doctor. ‘Mosquito nets can also offer protection if they are fine-meshed enough.’ The virus is mainly transmitted by so-called mosquitoes, i.e. very small mosquitoes up to 3 millimetres long, which are not kept out by conventional nets because the mesh is too large. Jan Felix Drexler recommends that pregnant women seek travel medical advice before travelling to risk areas, as long as the intensive infection process continues and the consequences of an Oropouche infection for unborn babies are not yet clear.
*Fischer C, Frühauf A, Inchauste L et al. The spatio-temporal ecology of Oropouche virus: a laboratory-based modelling study across Latin America. Lancet Infect Dis 2025 Apr 14. doi: 10.1016/S1473-3099(25)00110-0
About the study
The work was carried out as part of the project ‘Zoonosis Emergence across Degraded and Restored Forest Ecosystems’ (ZOE), which is funded by the EU Commission under the ‘Horizon Europe’ research framework programme, and was supported by numerous other funding bodies.
Image: Estimated baseline risk of infection with the Oropouche virus in Latin America. In most risk areas, cases of Oropouche fever have been described in the past or during the current outbreak. In some risk areas, however, no cases have been officially reported so far, but the environmental conditions could be favourable for the spread of the virus. © Charité | Anna Frühauf (Image from the original publication in The Lancet Infectious Diseases)
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