Dual respiratory virus infections

Objective: To determine the frequency, associated comorbid conditions, clinical presentations and morbidity related to dual respiratory virus infection (DRVI) in immunocompetent persons. Design: Eight prospective epidemiologic studies conducted between 1991-1995 were retrospectively reviewed for DRVI. Viral diagnostic techniques included cell culture, serology, and PCR. A DRVI was identified by any combination of positive results of viral diagnostic tests for two different respiratory viruses. Results: Sixty-seven of 1341 (5.0%) acute respiratory viral infections had two viruses identified. DRVI were detected from <1 year to 79 years of age, in both sexes and many races. Forty-two percent of patients with DRVI were a 4 years old. Fifty-eight percent of patients with DRVI had underlying chronic lung disease. DRVI were associated with upper respiratory tract illness, lower respiratory tract illness, including pneumonia, systemic influenza-like illnesses, and exacerbations of asthma or COPD. All of the common acute respiratory viruses were identified in DRVI; picornaviruses (mostly rhinoviruses) and influenzavirus A were the most common. Tissue culture detected ≥ 40% of DRVI, but the use of serology and PCR increased the rate of detection of DRVI. The rate of DRVI (11.6%) was highest in the studies that used cell culture, serology and PCR together. Patients with DRVI were hospitalized significantly more often than those with SRVI (46.3% vs. 21.7%, p<.01). Conclusions: DRVI occur at a low rate in immunocompetent patients of all ages, sex and race. The percentage of DRVI increased proportionally with the number of diagnostic methods used. Wider application of PCR to viral diagnosis will likely increase the rate of detection of DRVI.