Bacterial coinfection may have contributed to many deaths and much of the morbidity seen during the 2009 influenza A(H1N1) pandemic, suggest findings from an animal study by scientists from the National Institute of Allergy and Infectious Diseases.
In the study, mice were infected with the pandemic 2009 influenza A(H1N1) strain or another strain of H1N1 influenza that had been circulating seasonally prior to the pandemic; some of the animals in both groups were then inoculated with Streptococcus pneumoniae (Kash JC et al. mBio. 2011;2:e00172-11). Although all of the mice infected only with influenza virus survived, those coinfected with bacteria had much worse outcomes. All of the animals infected with the pandemic strain and S pneumoniae died after serious weight loss and lung damage. Although all mice coinfected with the bacteria and the seasonal flu strain survived, they also had weight loss and signs of lung damage.
Kuehn BM. Bacteria-H1N1 Coinfection. JAMA. 2011;306(16):1750. doi:10.1001/jama.2011.1541