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October 22, 2009

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“Superspreader” workers may trigger hospital outbreaks

Oct. 22, 2009
Courtesy PNAS
and World Science staff

Health-care work­ers who roam from pa­tient to pa­tient in a hos­pi­tal ward may play a dis­pro­por­tion­ate role in spread­ing pathogens, a the­o­ret­i­cal study sug­gests.

Lau­ra Temime of the Con­serv­a­toire des Arts et Métiers in Par­is and col­leagues used a math­e­mat­i­cal mod­el of a hy­po­thet­i­c in­ten­sive care un­it to de­ter­mine how easily com­mon hos­pi­tal-based in­fec­tions spread.

The mod­el at­tempted to sim­u­late the dif­fu­sion of germs in­clud­ing an­ti­biotic-resistant bac­te­ria such as the so-called en­te­ro­cocci or Staph­y­lo­coc­cus au­re­us.

The mod­el di­vid­ed health care work­ers in­to three groups: a “nurse-like” group, which made fre­quent vis­its to a small num­ber of as­signed pa­tients; a “physician-like” group, which made infre­quent vis­its to a larg­er num­ber of pa­tients; and a “peri­patet­ic” group, which, like a phys­i­cal ther­a­pist or ra­di­ol­o­gist, vis­ited all pa­tients in a ward dai­ly.

The mod­el showed in­fec­tion out­breaks in­creas­ing when work­ers failed to fol­low stand­ard hand wash­ing pro­ce­dures. But in­fec­tion rates in­creased by up to three times more when a per­i­pa­tetic health care work­er failed to wash his or her hands com­pared with a work­er from the oth­er groups, the re­search­ers added. 

The in­fec­tion rate from a sin­gle per­i­pa­tetic work­er fail­ing to wash their hands was equiv­a­lent to the in­fec­tion rate when 23 per­cent of all health care work­ers on the ward failed to hand wash, Te­mime and col­leagues con­clud­ed. 

The re­search­ers sug­gested that the un­usu­al pro­file of per­i­pa­tetic health care work­ers makes them po­ten­tial “su­per­spread­ers,” and that hy­giene meas­ures in hos­pi­tals may need to fo­cus on them.

The find­ings are re­ported in this week’s ad­vance on­line is­sue of the re­search jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces.

* * *

Health-care workers who roam from patient to patient in a hospital ward may play a disproportionate role in spreading pathogens, a theoretical study suggests. Laura Temime of the Conservatoire des Arts et Métiers in Paris and colleagues used a mathematical model of a hypothetical intensive care unit to determine how easily common hospital-based infections spread. The model attempted to simulate the diffusion of germs including antibiotic-resistant bacteria such as enterococci or Staphylococcus aureus. The model divided health care workers into three groups: a “nurse-like” group, which made frequent visits to a small number of assigned patients; a “physician-like” group, which made infrequent visits to a larger number of patients; and a “peripatetic” group, which, like a physical therapist or radiologist, visited all patients in a ward daily. The model showed infection outbreaks increasing when workers failed to follow standard hand washing procedures. But infection rates increased by up to three times more when a peripatetic health care worker failed to wash his or her hands compared with a worker from the other groups, the researchers added. The infection rate from a single peripatetic worker failing to wash their hands was equivalent to the infection rate when 23 percent of all health care workers on the ward failed to hand wash, the researchers concluded. The researchers suggest that the unusual profile of peripatetic health care workers makes them potential “superspreaders,” indicating that hygiene measures in hospitals may need to focus on them. The findings are reported in this week’s advance online issue of the research journal pnas.