Chattin' 'bout contact precautions: Endemic?

It's been a quiet week out here on the edge of the prairie. Temperatures plunged into the 40s at night and the cooler breezes have been amazing - a nice change from the mid-90's in Geneva last week. I'd like to publicly thank SAS for losing my luggage for 4 days and especially the folks who still talked to me during the meeting. Four days in the same pants - reminds me of a doctor's white coat!

One of the topics that came up at ICPIC and on twitter after the various contact precautions posts and JAMA viewpoints was whether a pathogen's prevalence is an important criteria to use when deciding between types or levels of infection control interventions to implement. Put another way, should we treat common, ie endemic pathogens like MRSA, differently than outbreak or novel pathogens like CRE?

Of course, the first difficulty with answering this question is that endemicity is local, like politics. For example, MRSA is only endemic in certain parts of the US (we have little at the Iowa City VA vs the Baltimore VA) and MRSA remains rare in the Netherlands. Clostridium difficile is common everywhere, except that when we visited Vietnam last year, we heard that it is less common in SE Asia. So, we can agree that it would be difficult to write national guidelines or mandates for specific pathogens if endemicity is an important parameter.

Another question I have is how can we define an endemic threshold?  If we were concerned about MRSA, is it the proportion of clinical S. aureus isolates with mecA? Or would the threshold be set around some level of admission prevalence - say 10%? This might depend on the pathogen and such factors as the colonization to infection ratio.

Finally, I do wonder if using endemic thresholds for deciding whether to relax infection control interventions runs counter to the risk of transmission in our ICUs and wards. One of the most important risk factors in acquiring a pathogen, say VRE, is the colonization pressure (proportion of other patients colonized with the bacteria) on the unit. Doesn't it then follow that as a pathogen becomes "more" endemic, however defined, that the individual risk to the "negative" patient increases. We can agree that it is harder to eliminate a pathogen as it becomes more prevalent or endemic. Yet, elimination isn't the only or even primary goal of infection prevention - it is to protect the individual patients and populations in our hospitals. Usually, endemicity is beyond our control, as there are many outside factors that can impede our efforts. But I don't think we should use endemic thresholds in our decision making.

Of course, we still need to ask basic questions like does the intervention work? Is it cost effective? And to bring this back to contact precautions, I see little evidence that contact precautions are more effective in CRE or CDI control vs MRSA. I also don't see that mortality rates are much higher in those pathogens where we agree to use contact precautions routinely (e.g. CRE) and where there is debate (e.g. MRSA). So there must be other factors driving the decision making, like availability of effective antibiotics, but I don't think endemic thresholds should be one of them.


  1. Dear Eli, I agree that is not easy to determine the endemic threshold, but all of us know which multiresistant bacteria are endemic and which are not in most of our hospitals. For example, 131 new cases of MRSA per year versus 1 case of Klebsiella with carabapenemase oxa 48 every two years.
    When I mesaure compliance of isolation measures in "endemic" cases, hand hygiene (hidden observer) is around 40%, when I do the same in a little outbreak of one or two cases of a CPE in the ICU, hand higiene compliance in the isolated patient is higher than 95%.I think that the difference in efficacy of isoloation measures are related to the level of alertness on the profesionals, that we, as infection control responsibles generate. It is much higher when we have one or few cases of rare and daunting microorganism than when we have another new case of MRSA or ESBL.

    1. Thanks for your comment Joaquin. I agree that endemic thresholds are highly local and the hospital epidemiologists/infection preventionists will know what's endemic. I would worry about using prevalence of an organism as a marker for healthcare worker compliance and then using that to decide where to apply certain levels of infection control interventions. After a brief period of fear, CRE will become more commonplace and then compliance will fall but we still may not have effective antimicrobials for CRE. Eventually, we need to develop infection control bundles that work with common and rare pathogens and can have higher levels of compliance. But you make very good points.

  2. Good read, makes me wonder why Clostridium difficile is less common in South east Asia. What are they doing that we are not.


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