More evidence of MRSA involvement in H1N1 flu

When the H1N1 pandemic started at the end of last April, few of the case-patients seemed to have any secondary bacterial infections. This was unusual: In the 3 20th-c pandemics, the only ones for which there are good records, bacterial pneumonias seem to have accounted for a high percentage of illness and death. But H1N1 was unusual in a number of ways, and so health authorities wrote down the lack of bacterial infections as one more quirk of this novel strain.

Comes now the CDC to say that while that may have been the case in the spring, it is not now. In a conference call conducted Monday for doctors, which I covered for CIDRAP, the agency said that out of 77 deaths for which it had excellent autopsy data (a small subset of the deaths so far), 22, or 29%, had some bacterial co-involvement. Among the 22, the leading bacterium was S. pneumoniae (or Pneumococcus), but S. aureus was the second leading cause, with 7 cases, and 5 of those cases were MRSA.

(There is not yet anything online from that call to link to. A transcript is promised, and the CDC reps conducting the call said the data will be out soon in the MMWR. I’ll update when possible.)

In fact, there is an emerging literature on the role of bacterial infections in illness and deaths in this flu, and an emerging consensus that bacterial infections are playing a bigger and more serious role than was thought at first. At the ICAAC meeting two weeks ago (more on that soon), KK Johnson et al of the Women’s and Children’s Hospital of Buffalo, N.Y., along with researchers from two other institutions, described two severe and ultimately fatal infections with H1N1 complicated by community-strain MRSA. The victims were children, a 9-year-old girl and a 15-year-old boy, who arrived at the emergency room several days after being seen for mild flu symptoms. Both children died of necrotizing pneumonia, one 11 days after being hospitalized and one 3 days. Cite (no link available): K.K. Johnson, H. Faden, P. Joshi, J. F. Fasanello, L. J. Hernan, B.P.Fuhrman, R.C.Welliver, J.K. Sharp and J. J. Schentag, “Two Fatal Pediatric Cases of Pandemic H1N1/09 Influenza Complicated by Community-Acquired Methicillin-Resistant Staphylococcus aureus (CA-MRSA),” poster G1-1558a.

Finally, there is one recent paper that is online, and it describes MRSA necrotizing pneumonia plus flu in an adult, not a child. It comes from Hong Kong, from a group that were the first to describe SARS pneumonia and thus have a lot of experience in surfing the early wave sof a pandemic. In this new paper in the Journal of Infection, they describe the death from necrotizing pneumonia of a healthy 42-year-old man who was in the hospital only 48 hours. They believe this is the first H1N1+MRSA death to be recorded in the medical literature, and so they use the opportunity to issue a warning to doctors: If a flu patient arrives with what appears to be secondary pneumonia, drugs that can treat MRSA must be prescribed, or the infection will flourish unchecked and death will result. The cite is: Cheng VCC, et al., Fatal co-infection with swine origin influenza virus A/H1N1 and community-acquired methicillin-resistant Staphylococcus aureus, J Infect (2009), doi:10.1016/j.jinf.2009.08.021.

We’ve been talking since the beginning of this pandemic, and before that, about the unique hazards of MRSA + flu coinfection. (Archive of posts here.) It’s important ot understand that the bacterial pneumonias now being recorded are not only due to MRSA; Pneumococcus is playing a role as well. That is important because, unlike MRSA, we have vaccines against Pneumococcus; in the United States, one vaccine is approved for children and a second related one for adults. With no MRSA vaccine anywhere, and no H1N1 vaccine yet, it is worth considering whether to take a pneumococcal vaccine for additional protection as this pandemic unfolds.


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