ObjectiveTo compare the clinical characteristics of inpatients with different influenza subtypes, so as to identify the subtypes at an early stage.MethodsA retrospective case study was conducted, using influenza surveillance data from January 1st, 2016 to December 31st, 2018 at a tertiary surveillance outpost hospital in Chengdu. Patients diagnosed with different subtypes of influenza by nucleic acid testing or virus isolation and culture were investigated, and their clinical characteristics, laboratory test results, and prognosis were analyzed and compared among the four subtypes including H1N1, H3N2, Victoria (BV), and Yamagata (BY).ResultsThere were 127 inpatients with laboratory-confirmed influenza. Among the confirmed influenza patients, 85.8% (109/127) had low or normal white blood cell counts, and 78.8% (89/113) had abnormally high procalcitonin levels. Among the patients with different subtypes, statistical differences existed in age (P<0.001), low or normal white blood cell count (P=0.041), positive bacteria/fungus/mycoplasma/chlamydia culture (P=0.001), kidney damage (P=0.013), outcome at discharge (P<0.001), and hospitalization expenses (P=0.016). However, there was no statistical difference in gender, clinical symptoms, liver damage, cardiac damage, or length of hospital stay (P>0.05).ConclusionThe infection of influenza can lead to severe clinical complications or even death. The outcomes of patients with influenza A may be more severe. An elevated procalcitonin level can be detected in quite a few patients with influenza.