Report questions value of handwashing to fight flu
Last Updated: Thursday, October 1, 2009 | 4:59 PM ET
The effectiveness of handwashing to prevent the spread of flu has come into question.
A news article in Thursday's online issue of the Canadian Medical Association Journal points to a Canadian report from 2007 that concluded there is no evidence that proper hand hygiene prevents transmission of flu viruses.Ontario Premier Dalton McGuinty showed Alianna Craig, 5, and her classmates at Toronto's Rolph Road Public School how to wash their hands properly on Sept. 8. (Chris Young/Canadian Press)
Although the report by the Council of Canadian Academies was commissioned by the Public Health Agency of Canada, PHAC still recommends handwashing to prevent the spread of flu.
Hand hygiene is touted as the major mode of interrupting the spread of flu, and plays a central role in influenza-control guidelines for both seasonal and pandemic disease, Thursday's report said.
The assumption mainly stems from several randomized controlled trials that showed routine hand hygiene five times daily significantly decreases the risk of catching respiratory illnesses.
Most acute respiratory diseases are caused by viruses, but since none of the studies tested for that, the studies do not offer any information about whether handwashing helps limit the spread of influenza in particular, the report's authors said.
Current evidence suggests flu viruses are mainly transmitted at a short range of one to two metres by inhaling particles from someone who is infected. The virus can also survive on surfaces, and theoretically could be transmitted by contaminated hands and surfaces, according to the report.
Handwashing recommendations are therefore based on practicality rather than evidence, says the report, which is based on the findings of a 13-member panel of experts chaired by Dr. Donald Low, microbiologist-in-chief at Mount Sinai Hospital in Toronto.
Low wasn't available for an interview on Thursday, but he told the journal that handwashing, "is a simple thing to do and it may protect you from some other illnesses."
The College of Family Physicians of Canada is trying to sort out the contradictory information and provide a summary to help family doctors advise their patients, CMAJ said.
The panel also looked at whether masks help protect against the transmission of flu viruses.
Mask type matters
People spew particles of various sizes from their mouth when they talk, laugh, cough and sneeze.
While larger particles fall to the ground, smaller ones in the range of 0.1 to 100 microns can stay in the air for seconds to days, depending on conditions such as humidity and airflow. It's these smaller particles that can be inhaled deep into the respiratory tract, the report said. A woman puts on a protective mask to protect against SARS at a wash station at the entrance to North York General Hospital in Toronto in 2003. (Kevin Frayer/Canadian Press)
It concluded surgical masks that allow air in the sides don't offer much protection. The N95 respirator — a moulded mask frequently used in industrial workplaces — can help protect people, since they are designed to fit tightly on the face and block particles as small as 0.1 microns.
A separate study released Thursday in the Journal of the American Medical Association concluded even surgical masks can be helpful in preventing spread of the virus.
Dr. Mark Loeb of McMaster University in Hamilton, Ont., and his colleagues conducted a randomized, controlled trial of 446 nurses in the province to compare the surgical masks with N95 respirators for protecting health-care workers from flu.
In the study, 225 nurses were assigned to wear surgical masks and 221 received the fitted N95 respirator when caring for patients with a fever and respiratory illness.
During last year's flu season, influenza infection occurred in 50 nurses (23. 6 per cent) in the surgical-mask group and in 48 (22.9 per cent) in the N95 respirator group, the researchers found.
The findings apply for routine care, not when there is high risk of exposure to aerosols, such as intubation, "where use of an N95 respirator would be prudent," the study's authors concluded.
Health officials say respirators needed to be sealed properly, which can be more of a problem for children or men with beards.
The Public Health Agency of Canada maintains there is substantial evidence that handwashing helps prevent the flu, and discourages the wearing of masks because people tend to use them improperly. The agency is reviewing the latest evidence.
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