Influenza and other respiratory virus infections in outpatients with medically attended acute respiratory infection during the 2011-12 influenza season

Background Respiratory tract infections are a major cause of outpatient visits, yet only a portion is tested to determine the etiologic organism. Multiplex reverse transcriptase polymerase chain reaction (MRT-PCR) assays for detection of multiple viruses are being used increasingly in clinical settings. Methods During January-April 2012, outpatients with acute respiratory illness (7days) were tested for influenza using singleplex RT-PCR (SRT-PCR). A subset was assayed for 18 viruses using MRT-PCR to compare detection of influenza and examine the distribution of viruses and characteristics of patients using multinomial logistic regression. Results Among 662 participants (6months-82years), detection of influenza was similar between the MRT-PCR and SRT-PCR (=0 center dot 83). No virus was identified in 267 (40.3%) samples. Commonly detected viruses were human rhinovirus (HRV, 15 center dot 4%), coronavirus (CoV, 10 center dot 4%), respiratory syncytial virus (RSV, 8 center dot 4%), human metapneumovirus (hMPV, 8 center dot 3%), and influenza (6%). Co-detections were infrequent (6 center dot 9%) and most commonly occurred among those <18years old. In regression analyses, compared with non-viral illnesses, RSV and hMPV were significantly more frequent in children and less frequent in 18- to 49-year-olds than in those 50years (P=0 center dot 01), fever was more common in hMPV and influenza infections (P=0 center dot 008), nasal congestion was more frequent in CoV, HRV, hMPV, influenza and RSV infections (P=0 center dot 001), and body mass index was higher among those with influenza (P=0 center dot 036). Conclusions Using MRT-PCR, a viral etiology was found in three-fifths of patients with medically attended outpatient visits for acute respiratory illness during the influenza season; co-detected viruses were infrequent. Symptoms varied by viral etiology.