Postnatally Acquired Dengue Fever Presenting as Persistent Fever and Thrombocytopenia in a Neonate: A Rare Case Report

Dengue fever is a major public health concern in tropical and subtropical regions, including India. While it is common in older children and adults, its occurrence in neonates is rare, possibly due to the protective effect of maternal antibodies, which typically wane over the first 6-12 months of life. Neonatal dengue can occur through vertical transmission from a symptomatic mother, where the presentation is at birth. However, very rarely, postnatal acquisition can occur in an otherwise healthy baby via the bite of an infected Aedes mosquito. Here, we present a unique case of postnatally acquired dengue fever in a term baby, wherein the initial symptoms were attributed to sepsis. However, the lack of response to antimicrobials and sterile cultures raised suspicion of an alternative diagnosis for which further investigations were planned. Owing to the endemic nature of the disease, dengue serology was included in the panel, which turned out to be positive. This case is unique in terms of presentation in the late neonatal period, despite a positive dengue serology in an otherwise asymptomatic mother, the presence of hepatosplenomegaly in the baby, severity of the illness, and a lack of typical clinical features such as rash. This report highlights the diagnostic challenges, management strategies, and outcomes, drawing parallels with existing literature to emphasise the importance of considering dengue in the differential diagnosis of neonatal sepsis in endemic settings, particularly where outbreaks are frequent during the monsoon and post-monsoon seasons.