A-282 Detection of anti-Oropouche virus-specific IgM in a patient panel from a Zika virus epidemic area in 2015 / 2016

Background Oropouche virus (OROV), an arbovirus mainly transmitted by midges, has recently been reported to cause large outbreaks of Oropouche fever in endemic and non-endemic areas of South America. Symptoms are similar to those of infections with other arboviruses. As arboviruses can share the same endemic regions, infection and co-infection with another arbovirus is possible even during epidemics. This study investigates the presence of antibodies against OROV in patient sera obtained in Colombia between 2015 and 2016 during a Zika virus outbreak. Methods Sera from 50 patients with clinical symptoms typical of arbovirus infection (one with Guillain Barré syndrome) were tested using anti-Zika virus, anti-OROV, anti-dengue virus, anti-chikungunya virus and anti-Mayaro virus ELISAs (all from EUROIMMUN). Results In 10/50 (20%) samples, the presence of anti-OROV IgM was detected. In 5/10 sera, only anti-OROV IgM was identified. 1/10 was anti-OROV IgM positive and borderline for anti-OROV IgG as well as anti-Mayaro virus IgM and anti-Zika virus IgA. In 4/10 sera, anti-OROV IgM was present and additionally antibodies against other arboviruses. One of those samples was borderline for anti-Mayaro virus IgM, two were positive for anti-Zika virus IgA, indicative of acute Zika virus infection, and one was positive for anti-chikungunya and anti-Mayaro virus IgM, which rather suggests an alphavirus infection. Conclusion Using the EUROIMMUN Anti-OROV ELISA (IgM and IgG, RUO) we have shown that OROV is likely to have been circulating in Colombia as early as 2015/2016. The data highlight the relevance of differential diagnosis especially during epidemics when the diagnostic focus may be primarily on the epidemic-causing virus.