Bacterial coinfections played a role in almost one-third of fatal cases of pandemic influenza A(H1N1) in the United States, based on data from 77 patients.
“These findings confirm that bacterial lung infections are occurring among patients with fatal cases of 2009 pandemic influenza A (H1N1) and underscore both the importance of pneumococcal vaccination for persons at increased risk for pneumococcal pneumonia and the need for early recognition of bacterial pneumonia in persons with influenza,” researchers wrote (MMWR 2009;58:1-4).
The investigators found evidence of concurrent bacterial infection in lung specimens from 22 of 77 patients (29%) with fatal cases of pandemic H1N1 infection. The specimens were submitted to the CDC by medical examiners and local health departments between May 1 and Aug. 20, 2009.
A total of 10 fatal cases were coinfections with Streptococcus pneumoniae, 6 were Strept. pyogenes, 7 were Staphylococcus aureus, 2 were Strep. mitis, and 1 was Haemophilus influenzae.
Four of the fatal cases involved multiple pathogens. The age of the patients ranged from 2 months to 56 years, with an average age of 31 years. The 22 patients were divided evenly by sex. The average duration of illness was 6 days, based on data from 17 of the 22 coinfection cases for whom this information was available.
Medical history was available for 21 of the coinfection patients, and 16 of these had underlying medical conditions “that were known to increase the risk for influenza-related complications,” the investigators wrote.