Masks as good as N95 respirators in fighting flu

With concerns of a flu pandemic on the rise, Canadian researchers have determined that surgical masks are not inferior to N95 respirators in protecting health care workers from contracting H1N1 or other forms of influenza.

Writing in the Journal of the American Medical Association (November 4, 2009, Vol. 302:17, pp. 1865-1871), Mark Loeb, M.D., M.Sc., and colleagues from McMaster University in Hamilton, Ontario, Canada, noted that data is sparse about the effectiveness of the surgical mask compared with the N95 respirator for protecting health care workers against influenza.

"Given the likelihood that N95 respirators will be in short supply during a pandemic and not available in many countries, knowing the effectiveness of the surgical mask is of public health importance," the researchers noted.

Between September 23-December 8, 2008, they conducted a randomized controlled trial of 446 nurses in emergency departments, medical units, and pediatric units in eight Ontario tertiary care facilities. Two hundred twenty-five nurses received surgical masks, while 221 received a fitted N95 respirator. The nurses were to wear the masks or respirators when caring for patients with febrile respiratory illness during the flu season.

The primary outcome was laboratory-confirmed influenza measured by polymerase chain reaction or a 4-fold rise in hemagglutinin titers. Effectiveness of the surgical mask was assessed as "noninferiority" of the surgical mask compared with the N95 respirator.

According to the researchers, influenza infection occurred in 50 nurses (23.6%) in the surgical mask group and in 48 (22.9%) in the N95 respirator group (p = .86). Even among nurses who had an increased level of the H1N1 flu, the study demonstrated that the surgical mask was not inferior to the N95 respirator for H1N1, they noted.

"Our data show that the incidence of laboratory-confirmed influenza was similar in nurses wearing the surgical mask and those wearing the N95 respirator," they wrote.

In routine health care settings, particularly where the availability of N95 respirators is limited, surgical masks appear to be comparable to N95 respirators for protecting health care workers against influenza, the researchers concluded.