So I’m really quite interested in seasonality of infections. I first became interested in it when looking at increases in E. coli bacteraemia for ARHAI (report here) because of Jennie Wilson’s excellent paper showing seasonality of gram negative bacteraemia, echoed by similar observations and conjecture on warmer weather, more infection. This is true in hospitals as well as the community. Why would this be? We have tussled with increasing E. coli bacteraemia in the UK for a few years now. Goes up every summer, does not return to the baseline, goes up again next summer etc., etc.. Other countries have also reported this. I have heard some suggest this is due to longer hours of daylight leading to more barbeques and more sexual activity. Given that the majority of infections in the UK are >70 years of age, my senior years have no fears for me then.
Or perhaps is it something more basic? Do the elderly drink more in summer to make up for fluid loss due to a warmer climate? I suspect not. Do hospital nurses keep an eye on how dehydrated patients become when temperatures rise? Do they notice this apart from the effect on themselves? Not unintentionally but again, I suspect not.
Now we have two papers (Spinal and other surgery), albeit from the same group, suggesting a seasonal link for SSI. Is this temperature-related? Staph aureus is of course more tolerant to salt (Yes, I know that we men ‘sweat’ whilst the ladies ‘glow’), could what other effects does warmer weather have on the skin? Opening of pores maybe? Or is it that during the summer the effect of senior surgeons taking leave means that more cases are undertaken by less senior staff who, it has been shown, have higher complication rates.
What effect does ambient temperature really have on infections? I have often wondered why Scandinavia is always green on an MRSA chart whilst southern Europe sits firmly in ‘Club Red‘. Does this relate to the climate? Should we dish out pre-operative Chlorhexidine, especially prioritising the summer? How could we achieve the all-important compliance, especially if undertaken before admission since compliance is notoriously low? For bloodstream infections that are often related to the urogenital tract, is the solution to the problem of increasing E. coli bacteraemias really less catheters? In reality catheters comprise <10% of related BSIs, or is getting the elderly to drink more so they are less dehydrated and prone to UTIs that we struggle to treat because of increasing resistance more of a priority?
Ah well, that’s a ‘public health’ issue and unlikely to be solved in my lifetime.. (or anyone else’s for that matter)
2 thoughts on “Hot stuff?”
Looked at this recently at our Maltese hospital; our winters go down to 8 degrees and then up to 40 degrees for several months in summer. There was absolutely no seasonality for Staph aureus but a very clear seasonal pattern for E. coli. However it was the opposite to that reported in the UK and Germany… i.e. incidence was highest in winter and lowest in summer!
Also it only applied for blood cultures taken at A&E (i.e. community cases) but disappeared when assessing only E. coli bacteraemias from blood cultures taken after 48 hours of admission.
Of course Malta bucks the trend! I think that (the E. coli seasonality) is the same in the UK, present in the community but not the post-48 hour.