Introduction:

Influenza is an acute respiratory disease with high mutation and transmission capacity, associated with seasonal epidemics and pandemics. In Bolivia, the department of Santa Cruz reported an increase in cases in 2025, which led to the declaration of a red alert. The aim of this study is to describe the epidemiological and clinical characteristics of patients hospitalized with influenza at Hospital Obrero No.3 in Santa Cruz, Bolivia.

Material and Methods:

Observational, descriptive study in patients over 15 years of age hospitalized between January 1 and May 17, 2025, with confirmed influenza diagnosis by reverse transcription polymerase chain reaction (RT-PCR). Sociodemographic and clinical variables, comorbidities, vaccination status, viral subtype, admission to the intensive care unit, and discharge outcome were analyzed.

Results:

A total of 88 patients were included. Most were over 60 years old (64%) and had comorbidities (86%), mainly hypertension (40%) and diabetes (32%). Only 17% were vaccinated. The most frequent symptoms were cough (100%), fever (97%), and dyspnea (97%). The predominant subtype was A(H1N1) pdm09 (97%). Twenty-five percent required admission to the intensive care unit, and 24% died.

Discussion:

Severe influenza cases in Santa Cruz were concentrated among older adults with comorbidities, low vaccination coverage, and predominance of the A(H1N1) pdm09 subtype. The findings highlight the need to strengthen vaccination and epidemiological surveillance to reduce the disease burden.