Incidence and Risk Factors of Pneumonia in Hospitalized Patients with Seasonal Influenza A or B

Abstract

BackgroundMost patients with influenza recover spontaneously or following treatment with an anti-viral agent, but some patients experience pneumonia requiring hospitalization. We conducted a retrospective review to determine the incidence and risk factors of pneumonia in hospitalized patients with influenza A or B.MethodsA total of 213 patients aged 18 years or older and hospitalized with influenza between January 2012 and January 2015 were included in this study. A reverse-transcriptase polymerase chain reaction assay was used to detect the influenza A or B virus in the patients' sputum samples. We collected demographic and laboratory data, combined coexisting diseases, and radiologic findings.ResultsThe incidence of pneumonia was higher in patients in the influenza A group compared to those in the influenza B group (68.6% vs. 56.9%), but this difference was not statistically significant. The presence of underlying respiratory disease was significantly associated with pneumonia in the influenza A group (adjusted odds ratio [OR], 3.975; 95% confidence interval [CI], 1.312–12.043; p=0.015). In the influenza B group, the white blood cell count (adjusted OR, 1.413; 95% CI, 1.053–1.896; p=0.021), platelet count (adjusted OR, 0.988; 95% CI, 0.978–0.999; p=0.027), and existence of an underlying medical disease (adjusted OR, 15.858; 95% CI, 1.757–143.088; p=0.014) were all significantly associated with pneumonia in multivariate analyses.ConclusionThe incidence of pneumonia was 65.7% in hospitalized patients with influenza A or B. The risk factors of pneumonia differed in hospitalized patients with influenza A or B.

Factors Affecting the Incidence of Hospitalized Pneumonia after Influenza Infection in Korea Using the National Health Insurance Research Database, 2014–2018: Focusing on the Effect of Antiviral Therapy in the 2017 Flu Season

“…In the Simmerman et al 12 study, it was shown that older patients or those with certain underlying diseases are more likely to develop pneumonia among hospitalized patients. According to the Chu et al 13 study, the incidence of pneumonia after influenza infection in hospitalized patients was 65.7%. Risk factors for the development of pneumonia were identified by age, respiratory disease, and underlying disease.…”

“…Risk factors for the development of pneumonia were identified by age, respiratory disease, and underlying disease. 13 14 When investigating factors affecting incidence of pneumonia after influenza infection, the result from our study using the claims data included age, preceding chronic diseases, and underlying diseases. It was similar to that from previous studies using medical records of hospitals.…”

Risk Factors for Pneumonia and Death in Adult Patients With Seasonal Influenza and Establishment of Prediction Scores: A Population-Based Study

“…While chronic diseases have been reported as risk factors for serious complications in influenza [ 2 , 16 ], such factors for pneumonia are not yet fully established. Even though several hospital-based studies have identified chronic respiratory disease and older age as relevant risk factors for pneumonia [ 14 , 28 ], it remains unclear whether these risk factors are applicable to general populations because of the potential selection bias in those studies; specifically, patients admitted for influenza symptoms would be more likely to be already critically ill at the time of admission or to have a serious underlying disease. Our large-scale population-based study also determined that older age and chronic respiratory disease were independent risk factors for pneumonia, in addition to male gender, dementia, congestive heart failure, and diabetes.…”

An Uncommon Case of Secondary Organizing Pneumonia Due to Influenza Type B

“…It also emphasizes the importance of gathering any history relative to any preceding upper respiratory viral illness when suspecting pneumonia. The incidence of subsequent pneumonia in hospitalized patients has been shown to be 68.6% and 56.9%, respectively, for influenza types A and B [ 8 ]. Treatment with Oseltamivir alone has not been noted to prevent the development of SOP [ 9 ].…”