To investigate the clinical characteristics of a fulminant respiratory infection caused by human adenovirus type 55 (HAdV-55) in Beijing, and to raise the awareness and level of diagnosis and treatment of HAdV-55 respiratory infection.

Total of 48 patients diagnosed as acute HAdV-55 respiratory tract infection were treated in The 8th Medical Center of PLA General Hospital. The clinical information of patients were collected and analyzed, retrospectively, including symptoms, signs, results of laboratory examination [including blood routine, erythrocyte sedimentation rate, C-reactive protein (CRP), blood biochemistry, pathogen nucleic acid detection, etc.], treatment methods and prognosis. Patients were divided into pneumonia group (18 cases) and upper respiratory tract infection group (30 cases) according to with or without variative lung lesions on CT image. Data with normal distribution of before and after treatment of the two groups were compared with paired t test, and the proportion of symptom distribution were analyzed by chi-square test or Fisher exact probability test.

The average age of 48 patients was (20.6 ± 1.8) years old, and 83.3% (40/48) cases were initial entry to Beijing from urban or rural areas below secondary level. There were 58.3% (28/48) patients with the highest body temperature > 39℃, including 12 cases in pneumonia group and 16 cases in upper respiratory tract infection group (χ² = 0.823, P = 0.346); 84.6% (22/26) patients with sputum had yellow sputum, including 11 cases in pneumonia group and 11 cases in upper respiratory tract infection group (χ² = 0.142, P = 0.706), both without significant differences. Excepte for 6 patients treated for longer than 4 d, the average number of peripheral white blood cells in 42 patients was (9.03 ± 0.37) × 10⁹/L, there was no significant difference between pneumonia group [(9.08 ± 3.01) × 10⁹/L] and upper respiratory tract infection group [(9.01 ± 2.02) × 10⁹/L](t =-0.086, P = 0.932). Leukocyte count in 38.1% (16/42) patients were > 10 × 10⁹/L. The average CRP of 42 patients at first visit was (29.0 ± 17.2) mg/L, but there was no significant difference between pneumonia group [(30.2 ± 13.7) mg/L] and upper respiratory tract infection group [(28.3 ± 19.0)mg/L](t =-0.338, P = 0.737). The focus of pneumonia was basically located in the extrapulmonary zone, close to or connected to the pleura. Seven days after the patient’s temperature returned to normal, 7 cases were positive for HAdV nuclear acid among the 8 cases re-measured.

With high fever, yellow sputum, increased white blood cell and neutrophil count, and normal lymphocyte count, acute respiratory infection caused by HAdV-55 showed the characteristics of bacterial infection. The virus nucleic acid remains contagious within one week after the recovery of body temperature.