CDC keeps N-95 recommendation in H1N1 health worker guidance

Oct 14, 2009 (CIDRAP News) – The US Centers for Disease Control and Prevention (CDC) today issued eagerly awaited recommendations on pandemic H1N1 infection control in healthcare settings, which affirms its earlier guidance on N-95 respirators but spells out other options for when the respirators are in short supply.

New features in the 17-page report include criteria for identifying suspected influenza patients, suggested isolation periods, methods for balancing isolation precautions, and a more detailed hierarchy for prevention controls.

On Sep 3 the Institute of Medicine (IOM) affirmed the CDC's original guidance that healthcare workers caring for H1N1 patients wear fit-tested N-95 respirators, not surgical masks, as protection against the virus. The IOM report also called for more research on flu transmission and the efficacy of different respiratory protection methods.

Today's CDC guidance came with a caveat that the recommendations will be updated if new information becomes available.

N-95 use in pandemic H1N1 settings has been somewhat controversial; some professional groups oppose routine use of N-95s in flu settings because research on their efficacy has been inconclusive, and many workers find them uncomfortable to wear for long periods.

Recent research has not exactly settled the score. One unpublished study conducted at a hospital in Beijing found that N-95 respirators greatly outperformed surgical masks in protecting workers from flu viruses.

Another study published earlier this month in the Journal of the American Medical Association showed mask protection as rivaling that of N-95s. Some experts, though, have pointed to shortcomings of that study, such as a lack of a control group to account for health workers becoming infected outside the workplace

Hierarchy of preventive steps
In today's guidance the CDC advised facilities to use a hierarchy of controls to prevent flu transmission, starting with eliminating potential exposures such as postponing elective visits by patients who have influenza-like symptoms.

Engineering controls were next, which might involve installing partitions in triage areas or other public spaces. Administrative controls included employee vaccination and enforcing rules about working when sick and implementing respiratory or cough hygiene strategies.

Personal protective equipment (PPE) was ranked lowest on the hierarchy list, because it is the last line of defense when other measures can't be controlled.

The CDC emphasized that focusing on the three other prevention levels could reduce the reliance on PPE. "This is an especially important consideration during the current year, when shortages of respirators have already been reported by many healthcare facilities," the guidance states.

Specifics on N-95s, isolation
The CDC based its N-95 recommendation on several factors, including low levels of population immunity to the new virus, the rise of virus activity before the vaccine is available, and the increased risk of complications in some healthcare personnel, such as pregnant women.

Given that the respirators are likely to be in short supply, the CDC recommends reserving them for situations when protection is most important, such as during aerosol-generating procedures.

When shortages exist, the CDC urges facilities to consider prioritizing respirator use, keeping in mind workers' intensity and duration of exposure, personal risk factors for complications, and vaccination status. Workers who don't receive N-95s should receive surgical masks.

Because patients with more severe illnesses are likely to shed the virus longer than those with milder infections, the CDC recommends a longer isolation period for hospitalized patients.

It says isolation precautions for those with flu symptoms should continue for 7 days after illness onset or 24 hours after fever and respiratory symptoms subside, whichever is longer. Longer periods may be needed for certain patients, such as those with severe immune system compromise or those who may be shedding antiviral-resistant viruses.

Some opposing views
Today's release of the CDC guidelines drew a mixed reaction from the Society for Healthcare Epidemiology of America (SHEA).

Though SHEA praised the CDC's call for a multipronged approach for preventing flu transmission in healthcare settings, it knocked the N-95 respirator recommendation. SHEA said in a press release that it had urged the CDC, based on clinical and scientific evidence, to replace its N-95 recommendation with surgical masks for routine care of flu patients.

Mark Rupp, MD, president of SHEA and an infectious disease specialist at the University of Nebraska Medical Center, said in the statement that N-95s aren't necessary or practical for protecting healthcare workers and their patients against the H1N1 virus. "The best science available leaves no doubt that the best way to protect people is by vaccinating them," he said.

When the IOM issued its report last month, the Association of Professionals in Infection Control and Epidemiology (APIC) also criticized the recommendation to wear N-95s, saying that the guidance fails to take into account many practical and logistical problems linked to their use, such as discomfort, costs, shortages, and the difficulty of fit testing.

The World Health Organization recommends only standard and droplet precautions for healthcare workers who have routine contact with flu patients. Canada recently called for N-95 use only during aerosol-generating procedures.

SHEA suspects that the CDC was pressured by labor unions to recommend N-95 respirators, despite evidence that they don't offer any extra protection in droplet transmission diseases such as pandemic H1N1.

Continuing to recommend N-95s for routine care of flu patients might have unintended consequences, Rupp said in the statement. "We could actually put healthcare workers at greater risk by further reducing an already short supply of a device that is needed for high-risk procedures such as bronchoscopy by using it for routine care."

He said the N-95 debate has distracted hospitals and clinics from attention toward investing in other measures for controlling the spread of the virus, such as rigorous application of basic infection control tactics and rapid identification and separation of patients who have the virus.

"We understand the role of the CDC in providing reassurance during a period of evolving evidence, and we urge the CDC to continue to revisit its recommendations as new data becomes available," Rupp said.

See also:

Oct 14 CDC interim guidance on infection control measures for pandemic H1N1 in the healthcare setting

Oct 14 CDC Q&A document on above guidance

Sep 3 CIDRAP News story "IOM affirms CDC guidance on N95 use in H1N1 setting"

Sep 17 CIDRAP News story "Study on respirators versus masks hailed as landmark"

Oct 2 CIDRAP News story "Study suggests masks rival respirators for flu protection"

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