First outbreak of Oropouche Fever reported in a non-endemic western region of the Peruvian Amazon: Molecular diagnosis and clinical characteristics

Introduction: Oropouche fever is an under-reported and emerging infectious disease caused by Oropouche virus (OROV). Its incidence is under-estimated mainly due to clinical similarities with other endemic arboviral diseases and the lack of specific diagnostic tests. We report the first outbreak of Oropouche fever in a western region of the Peruvian Amazon in Huanuco, Peru. Methods: A transversal study was carried out during an outbreak in the western Region of Huanuco, Peru between January and July of 2016. Blood samples of 268 patients with acute febrile syndrome were collected and analyzed for OROV via RT- PCR and genetic sequencing. Results: Of all 268 patients, 46 (17%) cases tested positive for OROV. The most common symptoms reported were headache with a frequency of 87% (n = 40) followed by myalgia with 76% (n = 35), arthralgia with 65.2% (n = 30), retro-ocular pain 60.8% (n = 28) and hyporexia with 50% (n = 23). Some patients showed a clinical presentation suggestive of severe OROV infection, of which 4.3% (n = 2) had low platelet count, 8.6% (n = 4) had intense abdominal pain, and 2.1% (n = 1) had a presentation with thoracic pain. Conclusion: This study reports an outbreak of OROV in a region where this virus was not previously identified. The disease caused by OROV is an emerging, underdiagnosed infection that requires further research to determine its virulence, pathogenesis, host range and vectors involved in the urban and sylvatic cycles as well as identifying new genotypes to implement sensitive and specific diagnostic tools that can be applied to endemic regions.