BACKGROUND & OBJECTIVES: In India, certain geographic regions witness simultaneous outbreaks of two or more diseases like scrub typhus, dengue fever, malaria, leptospirosis and chikungunya during monsoon and post-monsoon period, sharing common indication of acute febrile illness. The objective of the present study was to assess the prevalence of coinfections among patients with acute undifferentiated fevers (AUF) admitted in a tertiary care hospital in the northern hilly state of Himachal Pradesh, India. METHODS: This was a hospital based open cohort study conducted over a period of two months (September and October) in 2016. All the patients above the age of 18 yr admitted in medical wards and fulfilling the definition of AUF were included. The patients diagnosed with dual infections were the subjects of the study. Standard guidelines were used for case definitions of scrub typhus, dengue, chikungunya, malaria and leptospirosis. RESULTS: Dual infections were noted in 16 patients admitted with AUF. The most common coinfection was scrub typhus and dengue, reported in 10 patients. Scrub typhus and leptospirosis coinfection was observed in three patients. Dengue and chikungunya was observed in one patient. Scrub typhus, dengue and vivax malaria was detected in one patient. Scrub typhus and vivax malaria was detected in one patient. Out of the 10 cases positive for both scrub and dengue, four had no history of travel outside Himachal Pradesh. All three cases positive for both scrub and leptospirosis were indigenous without any history of travel outside Kangra, Himachal Pradesh. The outcome of all the patients was with full recovery. INTERPRETATION & CONCLUSION: The study established the presence of coinfections (mainly dengue fever and leptospirosis) as a cause of AUF in the study area, which is a nonendemic region. The role of easily available and widely performed serological tests in the aetiological diagnosis of AUF is significant. Studies are required to determine the normal titres in the local population before using the imported commercially available serological tests in the diagnosis of AUF.