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The Oropouche virus, similar to the dengue and Zika viruses, is known to cause febrile illnesses. Recently, concerns have emerged regarding the potential impact of infections during pregnancy, which may lead to complications for unborn children. A team of researchers from Charité – Universitätsmedizin Berlin has published a pivotal study in The Lancet Infectious Diseases, revealing that the virus’s prevalence in Latin America is significantly higher than previously recognized. Their findings also indicate that climatic conditions are crucial in the virus’s spread.
Initially identified in the 1950s, Oropouche virus instances in Latin America have traditionally been reported infrequently, with most nations documenting only a handful of cases each year. However, an international research effort led by Prof. Jan Felix Drexler, head of the Virus Epidemiology laboratory at the Institute of Virology, has uncovered alarming evidence of underreporting. “Our findings suggest that Oropouche virus is vastly under-diagnosed in Latin America,” explains Drexler. “In some regions, we estimate that at least one in ten individuals has been infected with this virus at some point.”
The symptoms of the Oropouche virus are generally nonspecific, including fever, chills, headaches, joint pain, and occasionally nausea and skin rashes. While historically, the disease has been perceived as mild, recent evidence shows a concerning increase in reported cases, exceeding 20,000 since late 2023. This surge includes fatalities among otherwise healthy young women and suggests potential links between infections during pregnancy and severe outcomes, such as miscarriages or birth defects.
“Our understanding of this virus remains limited,” states Drexler. “The implications of infections, particularly concerning pregnancy, need more scrutiny. While it appears less likely than Zika to cause harm to infants, the risks cannot be overlooked.” Currently, there is no vaccine or targeted treatment available for Oropouche fever.
The researchers analyzed over 9,400 blood samples taken from individuals in Bolivia, Brazil, Colombia, Costa Rica, Ecuador, and Peru from 2001 to 2022. Results indicated that antibodies to the Oropouche virus were present in about 6% of samples across all regions, although with significant local variation. For instance, Costa Rica had an average of 2%, in contrast to over 10% in the Amazon region. Additionally, it was noted that residents at higher altitudes tended to have lower rates of prior infection compared to those living at warmer, lower altitudes. Yearly comparisons also show fluctuations in infection rates.
To understand what drives these infections, the research team utilized machine learning techniques to explore the connections between Oropouche virus infections and environmental and demographic factors. They found that climatic factors, particularly consistent temperatures and rainfall, play a significant role in the virus’s transmission. “It seems that recent weather phenomena, such as El Niño, have exacerbated the current outbreak,” Drexler elaborates. “We found no indication that changes in the virus itself account for the recent spike in cases. With climate change, the risk of Oropouche virus could expand even further.”
The study outcomes facilitated the estimation of Oropouche infection risks across Latin America, which were visually represented on a map. “The Amazon rainforest serves as the primary region for Oropouche virus,” says Drexler. “However, we also identified significant infection risks in specific areas of Central America, the Caribbean, and parts of southern and coastal Brazil.”
In light of the findings, preventive measures against Oropouche virus are emphasized. Drexler points out that alongside dengue and chikungunya, Oropouche virus ranks among the most prevalent viruses transmitted by insect bites in Latin America. He advocates for protective strategies against insect bites, particularly for individuals traveling to the region. “Wearing long clothing and using insect repellents, like DEET or icaridin, can be effective defenses. While mosquito nets offer some protection, the virus is primarily spread by small biting flies known as ‘no-see-ums’, which can often slip through standard netting.” Pregnant women are advised to consult healthcare professionals before traveling to areas with high infection rates, pending further research on the implications of Oropouche virus on fetal health.
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