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 andan 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 notadequate 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.