We analyzed medical charts preserved at the former First Army Hospital in Tokyo, Japan, and other affiliated hospitals. We previously described the clinical features of Spanish influenza among patients who were hospitalized at several study sites (2). Recently, additional records of patients affected by the second wave of disease during 1919–1920 were discovered, and these patients were the subjects of this study.

A total of 470 patients hospitalized during January 1919–January 1920 and diagnosed with Spanish influenza (as “epidemic cold” or “pneumonia due to epidemic cold”) fit the criteria for inclusion in the study. All patients were male soldiers or officers in the military of Japan. We collected data concerning patients’ general background and physical assessments, including lung sounds and fever charts. Among all patients, 8 (2%) died. We divided the patients who survived (n = 462, 98%) into 3 groups on the basis of hospitalization length: <10 days (28%), 11–20 days (34%), and >21 days (36%); we compared variables among the 3 groups. High fever was defined as a body temperature >38°C, and diphasic fever was defined as a body temperature >38°C after the initial fever had decreased to <37.5°C. Data on adventitious lung sounds collected during the hospitalization period were classified (on the basis of international classifications) as continuous, discontinuous, bronchial on the chest wall, and friction rub sounds (3). The study was approved by the Institutional Review Board of the National Center for Global Health and Medicine, Tokyo, Japan.

Of the 8 patients who died, 6 died within 10 days of hospital admission. Median length of hospitalization was 7 days for nonsurvivors and 16 days for survivors. The proportion of patients with audible adventitious lung sounds was significantly higher among those hospitalized for >21 days and among those who did not survive (Table 1(https://wwwnc.cdc.gov/eid/article/23/4/15-2097-t1)). Factors associated with the length of hospitalization in survivors (identified by using a Cox hazard proportional model) included diphasic fever, >6 days of continuing high fever from admission, a maximum respiration rate >26 breaths/min, and adventitious discontinuous lung sounds (Table 2(https://wwwnc.cdc.gov/eid/article/23/4/15-2097-t2))……”