Climate change and hospital pathogens

Do hospital pathogens like living in a Greenhouse?

Nothing should dare threaten your coffee.  So when Starbucks announced today that global climate change is threatening coffee supplies, you knew it would get media attention. What's a journalist without their coffee and cigarettes? (aaaack) What about hospital pathogens? Could climate change impact hospital infection rates. We thought it might. (Note: by we, I mean my colleague from Maryland Judy Johnson - She's now in Gainesville).

Back in 2006, Judy and I were sitting on a park bench (it was a nice day) discussing the upcoming ICAAC abstract deadline and pondering what we should submit, when she suggested we look for seasonal variation in Gram-negative pathogens.  Judy mentioned some data suggesting Gram-negative infections were more common in tropical countries and we also discussed the high incidence of Acinetobacter infections in troops returning from Iraq. Sure, we also knew that others had noticed summer peaks in certain pathogens, but the prior research didn't control for meteorologic factors and also combined summer data from across the entire US (hint: Maine ≠ Texas). Thus, we felt there was room for further exploration.

In our initial analysis, published in ICHE (2008), we reported that summer season (vs. winter) was associated with 28% more P. aeruginosa, 46% more E. cloacae, 12% more E. coli and 21% more A. baumannii clinical cultures over 8 years. Importantly, we found that for each 10°F increase in temp, there was a 17% increase in the monthly rates of infection caused by P. aeruginosa and also A. baumanii. Of course, this was a single center study, so we needed more proof.

Mike Eber and our group have just published a follow-up study in PLoS One looking at BSI data from 132 hospitals over 8 years. Using 211,697 inpatient blood isolates, we again found that Gram-negative organisms were more frequent in summer months ranging from 12.2% higher rates for E. coli to 51.8% higher for Acinetobacter spp. And more interestingly, we reported that independent of season, monthly humidity, monthly precipitation, and long-term trends, each 10°F rise in mean monthly temperature was associated with higher Gram-negative bacterial BSI frequencies ranging between 3.5% for E. coli to 10.8% for Acinetobacter spp.  Thus, warm temps = more Gram-negative bacteremias; that is, even a warm winter is a bad thing.  Lots more work to do to figure out why this might be, but I think it's an interesting first (or second) step. Cheers.

Note: Special thanks to Ramanan Laxminarayan and Extending the Cure for supporting this project.