Peripatetic health-care workers as potential superspreaders
- aConservatoire National des Arts et Métiers, F-75141 Paris, France;
- bInstitut National de la Santé et de la Recherche Médicale, U 657, F-75015 Paris, France;
- cInstitut Pasteur, PhEMI, F-75015 Paris, France;
- dFaculté de Médecine, Université du Val de Marne, F-94000 Creteil, France;
- eAssistance Publique-Hôpitaux de Paris, Hôpital Henri Mondor, Service de Réanimation Médicale, F-94000 Creteil, France;
- fInstitut National de la Santé et de la Recherche Médicale, U 707, F-75015 Paris, France;
- gUniversité Pierre et Marie Curie-Paris 6, UMR-S 707, Paris, France;
- hAssistance Publique-Hôpitaux de Paris, Hôpital Saint-Antoine, F-75012 Paris, France;
- iFaculté de Médecine Paris Ile de France Ouest, Université Versailles Saint Quentin, F-78035 Versailles, France; and
- jAssistance Publique-Hôpitaux de Paris, Hôpital Raymond Poincaré, Service de Médecine Aigue, F-92380 Garches, France
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Edited by Burton H. Singer, Princeton University, Princeton, NJ, and approved September 9, 2009 (received for review January 28, 2009)

Abstract
Many nosocomial outbreaks exhibit “superspreading events” in which cross-transmission occurs via a single individual to a large number of patients. We investigated how heterogeneity in Health-Care Worker (HCW) behaviors, especially compliance to hand hygiene, may cause superspreading events. In particular, we compared the superspreading potential of peripatetic (noncohorted) HCWs with that of other HCWs. We developed an agent-based model for hand transmission of a pathogen in a hospital ward. Three HCW profiles were allowed: 2 assigned profiles, one with frequent contacts with a limited number of patients, another with fewer contacts but with more patients; and one peripatetic profile, with a single daily contact with all patients. We used data from the literature on common nosocomial pathogens (Staphylococcus aureus, Enterococci). The average number of patients colonized over 1 month increases with noncompliance to hand hygiene. Importantly, we show that this increase depends on the profile of noncompliant HCWs; for instance, it remains low for a single noncompliant assigned HCW but can be quite large for a single noncompliant peripatetic HCW. Outbreaks with this single fully noncompliant peripatetic HCW (representing only 4.5% of the staff) are similar to those predicted when all HCWs are noncompliant following 23% of patient contacts. Noncompliant peripatetic HCWs may play a disproportionate role in disseminating pathogens in a hospital ward. Their unique profile makes them potential superspreaders. This suggests that average compliance to hygiene may not be a good indicator of nosocomial risk in real life health care settings with several HCW profiles.
Footnotes
- 1To whom correspondence should be addressed. E-mail: laura.temime{at}cnam.fr
Author contributions: L.T., C.B.-B., P.Y.B., and D.G. designed research; L.T., L.O., and Y.P. performed research; L.T., L.O., and P.Y.B. analyzed data; and L.T. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
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