Single, dual and multiple respiratory virus infections and risk of hospitalization and mortality.

Respiratory virus infections cause a significant number of hospitalization and deaths globally. This study investigated the association between single and multiple respiratory virus infections and risk of admission to a general ward, intensive care unit or death in patients aged 0-105 years (mean +/- s.d.=244 +/- 241 years), from North West England, that were tested for respiratory virus infections between January 2007 and June 2012. The majority of infections were in children aged 5 years. Dual or multiple infections occurred in 104% (1214/11715) of patients, whereas single infection occurred in 896% (10501/11715). Rhinovirus was the most common co-infecting virus (occurring in 695%; 844/1214 of co-infections). In a multivariate logistic regression model, multiple infections were associated with an increased risk of admission to a general ward [odds ratio (OR) 143, 95% confidence interval (CI) 12-17, P<00001]. On the other hand, patients with respiratory syncytial virus (RSV) and human parainfluenza virus types 1-3 (hPIV1-3), as a single infection, had a higher risk of being admitted to a general ward (OR 149, 95% CI 128-173, P<00001 and OR 134, 95% CI 1003-18, P=005, respectively); admitted to an intensive-care unit or dying (OR 15, 95% CI 120-20, P=0001 and OR 160, 95% CI 102-240, P=004, respectively). This result emphasizes the importance of RSV, hPIV and mixed infections and calls for research on vaccines, drugs and diagnostic tests targeting these respiratory viruses.