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J Med Virol. 2015 Sep;87(9):1456-61. doi: 10.1002/jmv.24210. Epub 2015 May 14.

Does virus-bacteria coinfection increase the clinical severity of acute respiratory infection?

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Postgraduate Program in Microbiology, Parasitology and Pathology, Universidade Federal do Paraná, Curitiba, Brazil.
Virology Laboratory, Universidade Federal do Paraná, Curitiba, PR, Brazil.
Hospital Epidemiology Division, Universidade Federal do Paraná, Curitiba, PR, Brazil.
Instituto Carlos Chagas, Fiocruz, Paraná, Brazil.
Bacteriology Laboratory, Universidade Federal do Paraná, Curitiba, PR, Brazil.
Faculdades e Instituto de Pesquisa Pel, é, Pequeno Pr, í, ncipe, Curitiba, Paraná, Brazil.


This retrospective cohort study investigated the presence of bacteria in respiratory secretions of patients hospitalized with acute respiratory infections and analyzed the impact of viral and bacterial coinfection on severity and the mortality rate. A total of 169 patients with acute respiratory infections were included, viruses and bacteria in respiratory samples were detected using molecular methods. Among all samples, 73.3% and 59.7% were positive for viruses and bacteria, respectively; 45% contained both virus and bacteria. Bacterial coinfection was more frequent in patients infected by community respiratory viruses than influenza A H1N1pdm (83.3% vs. 40.6%). The most frequently bacteria detected were Streptococcus pneumoniae and Haemophilus influenzae. Both species were co-detected in 54 patients and identified alone in 22 and 21 patients, respectively. Overall, there were no significant differences in the period of hospitalization, severity, or mortality rate between patients infected with respiratory viruses alone and those coinfected by viruses and bacteria. The detection of mixed respiratory pathogens is frequent in hospitalized patients with acute respiratory infections, but its impact on the clinical outcome does not appear substantial. However, it should be noted that most of the patients received broad-spectrum antibiotic therapy, which may have contributed to this favorable outcome.


acute respiratory infections; bacteria; influenza A H1N1pdm; respiratory viruses

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