Increased illness due to warming?

I do a terrible, wicked thing when I read press reports about scientific findings that surprise me. I look up the original journal article that the report is based on! Doing so very often gives me a chuckle. In the present case, I was surpised to hear how very ill I and my family must have been as we grew up in the very warm weather of the tropics. And, true to expectation the journal abstract behind the report below is amusing. It reveals something you would never guess from the article.

Excerpt: "A total of 211,697 inpatient BSIs were reported during 9,423 hospital-months. Adjusting for long-term trends, BSIs caused by each Gram-negative organism examined were more frequent in summer months compared with winter months, with increases ranging from 12.2% for E. coli (95% CI 9.2–15.4) to 51.8% for Acinetobacter (95% CI 41.1–63.2). Summer season was associated with 8.7% fewer Enterococcus BSIs (95% CI 11.0–5.8) and no significant change in S. aureus BSI frequency relative to winter."

In other words, some types of infection rose but other types FELL during summer. So conclusions about a systematic effect of warming are unjustified

What makes hospital-acquired infections so intractable? There’s no question that some of the organisms that cause them are tricky: MRSA hangs out on the skin and and in the nostrils, and E. coli resides in the gut, making it easy for them to be carried into hospitals undetected. Hospital workers’ poor performance on hand-washing is well-documented. And recently, researchers have begun to wonder whether hospitals have missed an opportunity by not emphasizing environmental cleaning —- of rooms, computers and equipment, for instance -— given how persistently some bacteria can linger.

A new paper in PLoS One, though, says there’s another factor contributing to the problem, one that has missed consideration until now: weather. An 8-year study of infection data from 132 hospitals finds that as outside temperatures rise, in-hospital infections with some of the most problematic pathogens rise also.

The analysis is a warning to healthcare institutions to be additionally on guard when it is warm outside. But the authors say it’s also a warning to the rest of us: If global climate change raises ambient temperatures, it could increase the likelihood of deadly hospital infections as well.

The study — by researchers from the University of Iowa, University of Maryland, Princeton University and the nonprofit Center for Disease Dynamics, Economics and Policy — used a privately maintained national database of almost 212,000 clinical bloodstream cultures taken between Jan. 1999 and Sept. 2006. It plotted the infections’ incidence against data on mean temperature and dew point and total precipitation from the US National Climate Data Center. It accounted for the potentially confounding effect of seasonal variation in hospital admissions.

And it found: From winter to summer, Gram-negative bacteria, the most problematic hospital pathogens, rose anywhere from slightly to dramatically. E. coli infections rose 12.2 percent; Pseudomonas infections rose 28.1 percent; Klebsiella infections rose 28.6 percent; and Acinetobacter infections rose 51.8 percent.

Moreover, for every 10-degree Fahrenheit rise in mean temperature, there was a rise in infections with those same Gram-negatives. The increase varied from 3.5 percent for E. coli to 10.8 percent for Acinetobacter, independent of any changes in the season, the humidity or amounts of precipitation. Changes in temperature also affected S. aureus and MRSA, but much less: Those infections rose 2.2 percent for every 10-degree change.


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