The incidence of respiratory tract infection in adults requiring hospitalization for asthma

Acute respiratory tract infections (RTI) are known to worsen asthma particularly in children. There are few studies in adults assessing the incidence of RTI in patients hospitalized with acute asthma. Aim: To document the incidence of RTI in adults hospitalized with acute asthma. Methods: A prospective study of patients with acute asthma admitted to the Department of Respiratory Medicine, Western Hospital Footscray, over a 12-month period. A control group was studied from elective surgical inpatients. Patients were investigated with serologic tests for Chlamydia, Mycoplasma, Legionella, and influenza A and B. Nasopharyngeal aspirate (NPA) samples were cultured for influenza, respiratory syncytial virus (RSV), adenovirus, parainfluenza, rhinovirus, and herpes simplex virus. If sputum was available, it was assessed with microscopy and culture. Blood cultures were taken if patients were febrile and all patients had a chest radiograph. Control subjects completed serologic tests and NPA. Results: Seventy-nine patients (33 male and 46 female) and 54 control subjects (26 male and 28 female) were studied. Two patients were enrolled twice. Mean (+/-SD) age of patients was 35+/-15 years (range, 16 to 66 years), and mean age of control subjects was 37+/-15 years (range, 18 to 69 years). In the patient group, 29 (37%) had evidence of recent RTI of which 23 were viral. Five of the control subjects (9%) had evidence of recent RTI (p<0.001). Twenty-four patients were positive on serologic and/or NPA culture. Five patients had positive serologic test results and/or NPA culture to two or more agents. Two patients tested positive on sputum, radiograph, and temperature criteria. Three patients tested positive on the basis of radiographic evidence of consolidation, blood neutrophilia, and temperature. Influenza A (13) and rhinovirus (9) were the most common infectious agents. Other agents identified were RSV (one), influenza B (two), adenovirus (one), and Mycoplasma (one). Influenza and rhinovirus infections occurred predominantly in late and early winter, respectively. Summer hospitalization did not relate to RTI. Conclusion: Thirty-seven percent of adult patients with acute asthma admitted to the Department of Respiratory Medicine over a 18-month period had evidence of recent RTI.