Clinical Characteristics and Prognosis of Influenza B Virus-Related Hospitalizations in Northern China during the 2017-18 Influenza Season: A Multicenter Case Series

Background. By weekly monitoring of China's influenza situation, Chinese National Influenza Center observed that the 2017-18 season was predominated by influenza B virus (IBV)/Yamagata. No studies regarding hospitalizations in adults with IBV infections have been performed. We aimed to describe the clinical characteristics of hospitalized patients with IBV infection in northern China. Methods. In this multicenter and retrospective study, we reviewed all consecutive adult patients with confirmed IBV infections at two level A tertiary teaching hospitals in northern China during the 2017-18 influenza season. Patients' clinical and diagnostic findings, as well as administered treatments and mortality data, were analyzed. Results. A total of 573 patients with a confirmed diagnosis of IBV infection were identified, of whom 22 cases were analyzed because of IBV-related hospitalization. Most patients were admitted to the intensive care unit (ICU) and had at least one underlying disease. The total in-hospital mortality was 27.3%. An elevated initial pneumonia severity index score, elevated direct bilirubin values, and lower platelet levels were associated with mortality (p=0.020, 0.013, and 0.049, respectively). The quick development of bilateral diffuse alveolar infiltrates was the most common imaging characteristics, following consolidation and pleural effusion(s). Risk factors such as HIV infection, pregnancy, underlying medical conditions, coinfections, and treatment delays were not associated with mortality. Conclusions. IBV should not be neglected because of its significant mortality. The elderly and patients with comorbidities, such as hypertension, diabetes, and connective tissue diseases, are more likely to have severe IBV-related pneumonia. Higher heart rates, direct bilirubin levels, initial PSI scores, and lower platelet levels are correlated with hospital mortality. Increased uptake in tetravalent influenza vaccine should be very helpful in preventing future cases of IBV hospitalizations.