Get your N95s ready; masks may not be enough for pandemic flu

CDC reconsiders respiratory guidance

Stock up on N95 respirators. The Centers for Disease Control and Prevention (CDC) in Atlanta is reconsidering its guidance using surgical masks in the event of pandemic influenza and soon may recommend using N95 filtering face-piece respirators.

At least two states — California and Minnesota — already have included N95 respirators in their state pandemic plans. That reflects concern that a novel strain of influenza could involve airborne transmission. Surgical masks are not respiratory protection and are used in droplet precautions to protect against splashes or sprays.

Although there are few studies focusing on the mode of influenza transmission, there is some evidence that even seasonal influenza may involve airborne spread.

"There's a lot of uncertainty about the modes of transmission and the relative contribution of droplets, aerosol, and contact transmission regarding influenza infection," says Max Kiefer, MS, CIH, associate director for emergency preparedness with the National Institute for Occupational Safety and Health. "We don't know which of those are most responsible for causing transmission and infection."

During a pandemic, a vaccine targeting the specific strain wouldn't be available for months, and antivirals may be in short supply. That makes personal protective equipment even more critical, Kiefer says.

"Given that uncertainty about transmission and the lack of normally available interventions such as vaccine and antivirals, it's prudent from a public health standpoint to take a higher level of precaution for our health care workers," says Kiefer, who participated in a CDC workgroup that included infection control experts from the CDC's division of healthcare quality improvement.

The CDC guidance will apply to health care workers as well as support personnel, such as dietary staff or housekeepers, who are in close contact with patients, according to a draft version. The CDC recommends the use of N95s with aerosol-generating procedures, but will suggest that hospitals may choose to use a higher level of protection, such as elastomeric or powered air-purifying respirators (PAPRs).

The AFL-CIO criticized the CDC for not going far enough with its revised guidance. Health care workers caring for patients with pandemic influenza should wear N100 respirators with an elastomeric seal and an inhalation valve, says Peg Semanario, MS, safety and health director with the AFL-CIO in Washington, DC.

"By definition, a pandemic agent will be very transmissible and quite lethal," she says. "If that's what you're dealing with, what you want to do is to provide people with the best protection you can. If we're in a situation where people are not being protected, [and] health care workers are getting sick, they're not going to come to work — and you shouldn't expect them to," she says.

Plan for the worst case

Industrial hygienists have long argued that surgical masks are not adequate protection for health care workers. At the recent conference of the International Society for Respiratory Protection, held in Toronto, industrial hygienists from Germany, the UK, and Canada advocated the use of N95s in a pandemic.

Even multiple surgical masks don't come close to the protection provided by a respirator, according to a Hong Kong study conducted during the SARS epidemic.1 When five surgical masks were worn instead of one, the filtration still was low, the researchers said. "[O]ur data show that no combination of multiple surgical masks was able to meet the requirements for a respirator," they concluded.

A pandemic likely would be much more widespread than the SARS outbreaks, and supplies of N95 respirators likely would be consumed quickly, infection control experts caution.

But supply and cost are not reasons to alter the level of preparedness, says Jon Rosenberg, MD, public health medical officer in the division of health care epidemiology and infection control for the California Department of Health Services.

"There's a temptation for health care facilities to say it's cheaper and easier to only prepare for droplets," he says. "If evidence of airborne transmission does emerge during a pandemic, they're not going to be able to provide adequate protection for their employees.

"If you don't plan for it, you're not going to be able to do it," he says.

Hospitals also should consider the perspective of health care workers who may be fearful of coming to work if they don't feel they have adequate protection, says Rosenberg. As part of pandemic planning, health care workers should receive training in droplet and airborne precautions, he says.

In fact, hospitals should prepare for the possibility of various modes of transmission and maintain ample supplies of other personal protective equipment, such as goggles, gowns, and gloves, says Deborah Levy, PhD, MPH, senior adviser for health care preparedness at the CDC.

"If you're totally focused on it being [spread by] droplets and you're focused on getting surgical masks, what happens if it ends up being one of those [strains] that has a lot of diarrhea and you've got contact issues?" she says. "From a preparedness standpoint, you should never focus on just one strategy."

Hospitals unsure about stockpiling

Yet pandemic influenza planning varies widely among states, local health departments, and health care facilities. A 2005 survey of 70 hospitals in Los Angeles County found that two-thirds did not have a pandemic influenza response plan, and one in four (28%) had antivirals available only on an "on-demand" basis.

While 39% of the hospitals said they were planning to purchase more personal protective equipment as part of preparedness, 35% were not sure about purchasing plans. (The Department of Public Health will update the survey in January 2007.)

Meanwhile, the Los Angeles County pandemic influenza plan emphasizes the importance of hand hygiene as the primary method to prevent transmission and cautions about the likely short supply of masks, it differs from the state plan by addressing the use of surgical masks: "Although there is a lack of evidence that the use of masks prevented transmission of influenza during previous pandemics, in the early phase of an influenza pandemic, it may be prudent for [health care workers] to wear masks when interacting in close face-to-face contact with coughing individuals to minimize influenza transmission. This use of masks is advised when immunization and antivirals are not yet available but is not practical or helpful when pandemic influenza has entered the community."

Once the CDC comes out with its guidance, the Los Angeles County plan will be updated, says public health nurse Donna Chartrand, RN, PHN. "We will have to harmonize our plan with the state and the [federal government]," she says.

For hospital planning, the most important advice is the simplest: Be flexible. Guidance may change based on the characteristics of a particular organism and the availability of vaccine or antivirals, says Levy.

"You've got to build in that flexibility so that when the scenario is not as you thought it would be, you're not stuck," she says.

In fact, planning is a continual process. If the current H5N1 avian influenza does not become easily transmissible among people, another influenza strain is likely to trigger a pandemic in the future, experts say.

"The one point of agreement is that many patients are going to require hospitalization [in a pandemic] and that it's important for governments and the health care industry to take steps to ensure that we can provide that health care," Rosenberg says.


1. Derrick JL, Gomersall CD. Protecting healthcare staff from severe acute respiratory syndrome: Filtration capacity of multiple surgical masks. J Hosp Infect 2005; 59:365-368.