Who’s most likely to spread infection in the hospital?

Originally published in MedPage Today

by Michael Smith, MedPage Today North American Correspondent

Good hand hygiene among healthcare workers is an important factor in preventing the spread of disease, but exactly how important depends on an individual’s job, researchers said.

In a mathematical model, so-called “peripatetic” workers — such as therapists or radiologists — were most likely to spread pathogens if they neglected hand hygiene, according to Laura Temime, PhD, of the Conservatoire des Arts et Métiers in Paris, and colleagues.

In contrast, so-called “assigned” workers — typically nurses and doctors — were less likely to spread pathogens, Temime and colleagues said online in Proceedings of the National Academy of Sciences.

In many nosocomial disease outbreaks, a single individual transmits the pathogen to a large number of patients — so-called “superspreading events,” Temime and colleagues said.

Using modeling techniques, they tried to pin down which types of healthcare workers were most likely to contribute to such events. They modeled the effects of neglecting hand hygiene by three different types of healthcare workers:

* Those who had frequent contact with a few patients, such as nurses
* Those with less frequent contact, but who saw more patients, such as doctors
* Those who typically saw all patients once a day, such as therapists

The first two types were classified as “assigned” in that they had responsibility for a specific set of patients; those in the last category were “peripatetic” and saw all patients.

The model tracked what would happen over a month if a single colonized patient were introduced into an 18-bed ward, under various assumptions about noncompliance with hand hygiene rules.

When all healthcare workers were compliant, the researchers said, the model predicted between 1.5 and 5.8 new cases over the month, depending on how transmissible the pathogen was.

The size of the outbreak increased from 13 to 17% if a single worker neglected hand hygiene — to between 1.7 and 6.8 cases on average over the month.

But the results were highly dependent on which workers neglected their hygiene, Temime and colleagues found.

For a worker such as a doctor, who saw many patients but infrequently, the increase ranged from 2% to 7%. But for a noncompliant peripatetic worker, the increase ranged from 73% to 238%.

Indeed, a completely noncompliant peripatetic worker produced disease spread similar to what was predicted if all staff neglected hand hygiene after 23% of patient contacts, the model showed.

One implication of the finding, Temime and colleagues said, is that measuring average compliance with hand hygiene rules, such as by overall use of hand rub products, may not be a good indicator of the real risk of spreading disease.

Peripatetic workers, they said, can play a “disproportionate role in disseminating pathogens in a hospital ward,” making them “potential superspreaders.”

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