Influenza and Bacterial Co-infections: a Deadly Duo

Bacterial Coinfections in Lung Tissue Specimens from Fatal Cases of 2009 Pandemic Influenza A (H1N1)

This is the title of a brief report on the CDC’s MMWR website (CDC = “Centers for Disease Control” and MMWR = “Morbidity and Mortality Weekly Report”).  It’s no longer breaking news but it is still an important piece of relevant information you don’t want to miss.  This was the first official article we noticed after having published our Special Report, “Superbugs: the Coming Deadly Global Pandemic“, which addressed the matter over which we expressed great concern, viz., various strains of opportunistic, multidrug-resistant pathogenic bacteria could end up being responsible for many, if not most deaths associated with any future influenza pandemic.  Be sure to take a look at the post, “But What About the Flu?” on our blog, MDR Superbugs and you’ll see why all the concern on our part.

The MMWR article states,

In previous influenza pandemics, studies of autopsy specimens have shown that most deaths attributed to influenza A virus infection occurred concurrently with bacterial pneumonia, but such evidence has been lacking for 2009 pandemic influenza A (H1N1). To help determine the role of bacterial coinfection in the current influenza pandemic, CDC examined postmortem lung specimens from patients with fatal cases of 2009 pandemic influenza A (H1N1) for bacterial causes of pneumonia. During May 1–August 20, 2009, medical examiners and local and state health departments submitted specimens to CDC from 77 U.S. patients with fatal cases of confirmed 2009 pandemic influenza A (H1N1). This report summarizes the demographic and clinical findings from these cases and the laboratory evaluation of the specimens. Evidence of concurrent bacterial infection was found in specimens from 22 (29%) of the 77 patients, including 10 caused by Streptococcus pneumoniae (pneumococcus). Duration of illness was available for 17 of the 22 patients; median duration was 6 days (range: 1–25 days). Fourteen of 18 patients for whom information was available sought medical care while ill, and eight (44%) were hospitalized. 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.” [Emphasis ours]

[BTN Comment:  Please notice that there is apparently no dispute about the fact that historically, “most deaths attributed to influenza A virus infection occurred concurrently with bacterial pneumonia”.  Since this has been the case, it would seem the possibility of “secondary infection” with the H1N1 pandemic would have been addressed earlier on.  In any event, we think bacterial pneumonias and co-infections will once again play a major role with respect to fatalities occurring during any serious influenza pandemic in the future.

With this small sampling of 77 cases, nearly 30% showed concurrent bacterial infection.  In previous pandemics, the number has been much, much higher and we think that will also prove to be the case this time around once all the data is in.  CDC elsewhere admitted that “Routine clinical tests used to identify bacterial infections among patients with pneumonia do not detect many of these infections. For example, <10% of patients who are hospitalized with clinically diagnosed pneumonia have blood cultures that are positive for bacterial infections.” In other words, unless the lab uses some pretty extensive, sensitive screening, there’s a good possibility many who are actually infected will, at least initially, go undetected. Therefore, the numbers of actual co-infections will likely turn out to be higher.

It is also worth noting that, once the bacterial infection/pneumonia set in, the onset of death was rapid, only a matter of days. Even for those who were hospitalized and treated. As we mentioned in the “Superbugs” report, our concern is whether many of those who end up dying as a result of influenza complications will turn out to have been previously colonized with any of a number of various strains of multidrug-resistant bacteria, in addition to MDR Streptococcus pneumoniae.

MMWR (cont’d): “CDC receives tissue specimens routinely from patients with confirmed or suspected infectious diseases and provides histopathologic, immunohistochemical, and molecular evaluations…Specimens were received from 77 patients who had 2009 pandemic influenza A (H1N1) virus infection confirmed before death (N = 41) or after death (N = 36). Of the 77 cases evaluated, 56 (72%) had at least some clinical information available, and 35 (45%) had preliminary autopsy reports submitted with the tissue specimens…

“Of the 77 confirmed cases evaluated, 22 had histopathologic, immnohistochemical, and molecular evidence of coinfection with an identified bacteria, including 10 cases with S. pneumoniae, six with S. pyogenes, seven with S. aureus, two withStreptococcus mitis, and one with H. influenzae; four cases involved multiple pathogens. The median age of the 22 patients was 31 years (range: 2 months–56 years); 11 (50%) were male. The cases were reported from eight states: California, Hawaii, Illinois, New Jersey, New York, Texas, Utah, and Virginia.

[BTN Comment:  Note that even from this small sampling, some cases of coinfection involved other pathogens besides pneumococcus, some including multiple pathogens. As we mentioned in our “Superbugs” Special Report, we are up against a growing and increasingly diverse army of varied pathogenic micro-organisms these days. Therefore, we don’t have a lot of confidence that CDC’s recommendation for pneumococcus vaccination will provide the kind of protection that will be required.

MMWR (cont’d): “Duration of illness was available for 17 of the 22 patients; median duration was 6 days (range: 1–25 days). Fourteen of 18 patients with information available sought medical care while ill, and eight were hospitalized. Of the seven hospitalized patients with information available, all required mechanical ventilation. Seven of nine patients with information available on antimicrobial therapy were treated with antibiotics. Sixteen of the 21 patients for whom previous medical history was known had underlying medical conditions that were known to increase the risk for influenza-associated complications (16 patients) or that were indications for vaccination with 23-valent pneumococcal polysaccharide vaccine (PPSV23) (15 patients).”

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