The CDC just reported a study of 77 people who died of the H1N1 swine flu, finding that 22 of those unfortunate 77 had evidence of bacterial coinfection in the lungs – meaning that bacterial pneumonia as well as the direct effects of viral H1N1 may have contributed to death.
In prior flu pandemics it is known that bacterial pneumonia was often responsible for many deaths. The initial viral infection seems to set the stage for a one-two punch.
In this newest study, bacterial coinfections caused by S. pneumoniae, H. influenzae, S. aureus, and group A Streptococcus were proven using modern techniques on postmortem lung tissue samples. Out of the 22 samples found to have bacterial infections, the most common pathogen isolated was Streptococcus pneumoniae.
These results cannot be used to determine the prevalence of bacterial coinfection in all fatal cases due to several limitations (including the fact that not all possible bacteria could be tested for, knowledge of the final cause of death in some patients was limited, and tissue samples may have been collected from unaffected portions of the lung).
The findings in this report also underscore the importance of managing patients with influenza who also might have bacterial pneumonia with both empiric antibacterial therapy and antiviral medications. In addition, public health departments should encourage the use of pneumococcal vaccine, seasonal influenza vaccine, and, when the vaccine becomes available, pandemic influenza A (H1N1) 2009 monovalent vaccine.
While I am certainly not perfect, nor in the vanguard, nor necessarily right, I have treated “patients with influenza who also might have bacterial pneumonia” with both Tamiflu and an antibiotic. I can imagine some colleagues at first glance cringing at what seems like unnecessary or indecisive over-prescribing. But treatment decisions are often made based upon the convergence of past experience, luck, and clinical judgement. It is reassuring when the evidence gives credence to what feels intuitive, and confirms that past is prelude in terms of our human history with viral influenza pandemics and bacterial pneumonia.
It may be helpful for patients and clinicians to be aware of this latest report from the CDC, and to redouble efforts to vaccinate those for whom pneumococcal and flu vaccines are indicated. The challenge to decide “is it viral or is it bacterial” exemplifies a way of thinking that tries to balance appropriate antibiotic use with over-prescribing that creates resistance and side effects. But the viral-bacterial dichotomy may not be mutually exclusive if we are to carefully consider this CDC report, and may better inform what treatment decisions should be made for those who are ill.