News & Events

Sept 16 2002 Bloomberg “Surgical Masks Don’t Stop Flu From Spreading”

U.S. to Review Masks as Study Shows Flu Gets Through (Update2)

By Tom Randall and Jason Gale

Sept. 16 (Bloomberg) — The U.S. government said it’s reviewing recommendations on the use of surgical masks to protect health-care workers from flu after a study showed they don’t help. Thicker, more expensive respirators should be used, the study found.

Surgical masks didn’t stop the spread of flu and other respiratory illnesses during a five-week study involving 1,936 health-care workers at 24 hospitals in Beijing last winter. Thicker versions designed to better fit the face, called N95 masks and made by 3M Co., reduced flu by 75 percent. The N95s cost 5 to 10 times more, said study author Raina MacIntyre, head of public health at the University of New South Wales in Sydney.

Surgical masks, worn by doctors since the 1918 flu pandemic to prevent the spread of infection, have been an icon of medicine, popularized on TV from the 1970s series, “M*A*S*H,” to today’s “Grey’s Anatomy.” They were widely used in outbreaks of H5N1 bird flu and SARS. In July, 3M said it would invest $20 million to boost supply of N95 masks by 10 percent. MacIntyre, the lead author, said surgical masks should be scrapped and replaced by N95s.

“This is a landmark study that will change most public health approaches,” said Lindsay Grayson, a professor of medicine at the University of Melbourne. “If you’re going to be truly protected, you’ll need an N95 mask. A number of governmental recommendations will need to be changed.”

Changing Guidelines

The U.S. is revising recommendations to health-care workers and is trying to decide how to allocate the limited supply of N95 masks, Anne Schuchat, director of the U.S. Centers for Disease Control and Prevention’s Center for Immunization and Respiratory Diseases, said today in an interview.

Masks to protect against the swine flu virus are on back- order through 2009, 3M Chief Executive Officer George Buckley said on a July 23 conference call.

Australia’s government currently recommends health-care workers use P2 respirators, the nation’s equivalent of N95s, when performing high-risk procedures on patients with swine flu, Kay McNiece, a spokeswoman for the nation’s health ministry, said in an e-mail. Surgical masks are recommended for health- care workers in lower-risk settings, she said.

“Surgical masks are probably most useful when worn by patients to catch respiratory droplets that otherwise might spread directly to their close contacts or contaminate surfaces,” McNiece said. “The government’s health experts will look closely at this study,” she said, adding the government has stockpiled 8.4 million P2 masks.

3M and Kimberly-Clark Corp. are among manufacturers that make respiratory masks sophisticated enough to prevent disease spread. Only masks rated N95 or above, which filter at least 95 percent of particles, are effective at blocking flu, according to the U.S. Department of Health and Human Services.

MedTecs International Corp., a Taiwan-based maker of surgical and N95-equivalent masks, said demand for the products has increased more than 20 times since the flu pandemic started and it’s looking at ways to increase production to meet orders.

The company has orders for both its surgical masks and more sophisticated FFP2 masks until next year, Clement Yang, the company’s chairman, said in a telephone interview today.

Not Ethical

“It would not be ethical to recommend surgical masks for health-care workers,” MacIntyre said in an interview prior to her presentation. “They have significant leakage around the face. The findings fit everything we know from the experimental data about the poor quality of filtration, the poor fit.”

MacIntyre presented her findings at an infectious diseases conference in San Francisco.

The pandemic virus mostly spreads through respiratory droplets expelled by speaking, sneezing or coughing, according to the World Health Organization. Anyone within 1 meter (3 feet) of someone with a fever, cough and other influenza-like symptoms is at risk of being exposed to potentially infective droplets, the Geneva-based agency said in May.

If masks are used to prevent spread, the strategy should be combined with other general measures to prevent transmission, WHO said.

Using a mask incorrectly “may actually increase the risk of transmission, rather than reduce it,” the United Nations health agency noted. “Proper use and disposal is essential to ensure they are potentially effective and to avoid any increase in risk of transmission associated with the incorrect use.”

While the CDC recommends N95 for doctors in contact with pandemic flu patients, many hospitals continue to use the cheaper and more comfortable surgical masks. In today’s study, workers in emergency departments received either N95 masks or surgical masks and were asked to wear them throughout their shifts.

Institute of Medicine

Health-care staffers who work in close contact with flu patients should wear the N95 masks, according to an advisory committee set up by the Institute of Medicine. The Washington- based group submitted its recommendations to the CDC and the Occupational Safety and Health Administration on Sept. 3.

To be effective, the N95 masks need to be worn for the duration of a health-care worker’s shift, not just around flu patients, said Allison McGeer, director of infection control at Mount Sinai Hospital in Toronto. She cited Toronto’s experience with SARS, when 80 percent of workers who developed the illness caught it from somebody they didn’t know was infected.

About 47 percent of those wearing the N95 masks reported discomfort, compared with just 10 percent using surgical masks, today’s study found. Some doctors and nurses said they had headaches or difficulty breathing. Health care workers will weigh the risk of serious illness when deciding whether to wear an N95 mask, especially for their entire shift, McGeer said.

“It is possible to do it; it’s not pleasant,” McGeer said of the tight-fitting masks. “In this pandemic, you are not going to get people to do that in North America.”

‘Extremely Uncomfortable’

“I don’t think it’s practical in a routine ward setting for people to be wearing an N95 mask,” said Malik Peiris, professor of microbiology at Hong Kong University. “It’s extremely uncomfortable.”

The masks can’t be worn by pregnant women, one group at risk of severe complications from swine flu, because they restrict oxygen intake, said Tawee Chotpitayasunondh, a flu specialist at Thailand’s health ministry, by phone today. They can’t be worn for more than 45 minutes at a time, he said.

Complaints against the masks didn’t prevent health workers from wearing them in the study. The research is the largest evaluation of the masks in a variety of hospital settings.

“It’s a very important piece of work,” said Dominic Dwyer, professor of immunology and infectious diseases at the University of Sydney. “With mask use, there is very little data on respiratory infections.”

The study was funded by the University of New South Wales. 3M helped train researchers on how to test the masks for a correct fit.

To contact the reporter on this story: Tom Randall in San Francisco at; Jason Gale in San Francisco at

Last Updated: September 16, 2009 06:08 EDT