Does Handwashing Prevent Transmission of Influenza?

[indigo girl]

Hand-Washing Won't Stop H1N1

http://www.newsweek.com/id/215435

"It's become conventional wisdom that simple soap and water can protect against the flu, but the science suggests otherwise."

In a speech to schoolchildren last week that had some conservative opponents up in arms, President Obama delivered at least one line that seemed incontestable: "I hope you'll all wash your hands a lot, and stay home from school when you don't feel well, so we can keep people from getting the flu this fall and winter." The Disney corporation is now marketing Musical Hand Wash Timers featuring characters like the Little Mermaid, and encouraging parents to "take precaution against swine flu" by teaching children to wash their hands correctly. "Studies prove that regular hand-washing dramatically reduces the spread of infection," says the Disney Web page, which links to the Centers for Disease Control and Prevention's Web site.

Thanks in part to this and other campaigns run by the CDC, it has become conventional wisdom that hand-washing is the best way to protect yourself from the H1N1 strain of influenza. But while hand-washing has been shown to be a great defense against the common cold and other respiratory diseases, it might not actually be that helpful against the influenza virus, including the H1N1 strain.

That's because there is virtually no evidence that people can catch the influenza virus from germs that they pick up on their hands, according to Arthur Reingold, head of epidemiology at the University of California, Berkeley, and codirector of the CDC-funded California Emerging Infections Program. Instead, humans are most likely to catch influenza by breathing in microscopic particles exhaled by infected people.

Reingold and other epidemiologists don't discount hand-washing as an important tool in public health: there is plenty of evidence that it prevents other nasty bugs, including the common cold, many respiratory infections, and viruses that cause diarrhea. But Reingold is bothered by the lack of science supporting the CDC's message, and he worries that the emphasis on a simple measure like hand-washing creates a false sense of security from H1N1 and tamps down the discussion of more difficult preventive measures. He said as much in an e-mail to the CDC this May. "I wouldn't care so much that we might be getting folks to improve handwashing . . . with what is likely to be incorrect information about its ability to prevent influenza" if the media and the court of public opinion weren't so quick to embrace it as the only solution at the expense of things like surgical masks, wrote Reingold in his letter to the CDC. While Reingold admits he doesn't know if masks would reduce transmission of the virus, he hypothesizes that they're more likely to be helpful containing exposure to the airborne virus than hand-washing, and should not be so easily discounted. (Other experts are skeptical of face masks because it's difficult to ensure proper use, or that people will wear them in the first place.)

Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases, says the CDC's emphasis on hand-washing is guided by the "science that supports hand-washing against respiratory infections in general." In particular, she cites a study conducted in Pakistan that showed that hand hygiene measures cut the rate of pneumonia in half. One of the unique features of swine flu--the fact that it causes diarrhea--also suggests to some that it could be transmitted on the hands like other diarrhea-causing diseases that do not belong to the influenza family. Schuchat stresses that the best way to protect yourself will be to get the vaccine once it becomes available in October, but adds that the CDC continues to believe that "contact precautions are useful with this flu."

But the ferrets and guinea pigs tell a different story, says Dr. Michael Osterholm, of the National Institutes of Health-supported Minnesota Center of Excellence for Influenza Research and Surveillance, and head of the University of Minnesota's Center for Infectious Disease Research and Policy. Researchers in the Netherlands used ferrets to study the transmission of H1N1 and found that the disease was efficiently transmitted by small airborne particles. An earlier study examining a different flu strain in guinea pigs found that the animals did not pick up the virus from contaminated cages. That suggests that you're not really safer from the flu virus if you scrub your hands, paws, or cages because the virus travels through the air. While there's not enough evidence to conclusively say the flu works the same way for humans, the current research suggests that the H1N1 flu travels mostly by air, not via hand-to-hand contact--and therefore won't be prevented through hand-washing.

"We don't want to create a crisis in confidence," Osterholm says, "but we have to be honest: the evidence doesn't show that hand-washing prevents the spread of the influenza virus."

Nevertheless, hand-washing is still your best defense against getting sick generally this fall--colds and other respiratory diseases are no fun, even if they don't sound as scary as swine flu. For that and other flu viruses, don't seek solutions at the sink: your best chance of avoiding H1N1 this fall is to get the vaccine once it becomes available.

[indigo girl]

Conflict emerges over value of handwashing as a preventive flu transmission measure

http://www.cmaj.ca/earlyreleases/1oct09_conflict_handwashing.shtml

There's no evidence that good hand hygiene practices prevent influenza transmission, according to a Council of Canadian Academies report commissioned by the Public Health Agency of Canada.

But N95 particulate respirator-type masks are a proven "final layer of protection" against even the smallest viral particles of influenza, says the Influenza Transmission and the Role of Personal Protective Respiratory Equipment: An Assessment of the Evidence report prepared by an expert panel on influenza and personal protective respiratory equipment, chaired by Dr. Donald Low, microbiologist-in-chief at Mount Sinai Hospital in Toronto, Ontario (http://www.scienceadvice.ca/documents/(2007-12-19)_Influenza_PPRE_Final_Report.pdf).

Despite those 2007 findings, PHAC still recommends handwashing as the primary preventive measure against flu transmission. The agency also states on its website that there is no evidence that wearing masks "will prevent the spread of infection in the general population. Improper use of masks may in fact increase the risk of infection."

Moreover, PHAC states in an email to CMAJ that "there is substantial evidence to support hand hygiene as a basic premise of infection prevention and control measures." The agency also indicated that its hand hygiene recommendations are based on a combination of expert opinion and evidence, including a recent Cochrane Collaboration systematic review (BMJ 2009;339:b3675).

But the contradictory evidence and recommendations on preventive measures and other pandemic (H1N1) 2009 issues leaves Canadian doctors at a loss as to the best advice to provide patients, says College of Family Physicians of Canada President Dr. Sarah Kredentser.

"The average family physician is confused and that's partly because there is a lot of conflicting evidence and things change day by day," Kredentser says, adding that there's a need for the experts to get the information right and then get it out quickly to family physicians. To that end, the College is now working with PHAC, the Canadian Medical Association and other bodies to craft a one-page influenza guideline for physicians to use in the community.

The absence of any kind of national guidelines or strategies "makes it tough for physicians in practice. In this kind of situation, physicians actually want to be told: What do I do? How do I triage patients? What steps do I take to keep the office open?" Kredentser says, adding that even providing vaccination advice to patients is problematic given the ongoing national controversy over an unpublished study that indicates that getting the seasonal flu vaccine may double the risk of contracting pandemic (H1N1) 2009.

According to the Council of Canadian Academies report, though, there's no conflicting advice regarding handwashing or the use of N95 respirators.

Low argues that the PHAC's hand hygiene recommendations "are not evidence-based." Noting that research on influenza transmission is limited, he adds that in the absence of adequate evidence, recommendations are often just "expert opinion."

Hand washing is based on practical, rather than scientific, considerations, he says. It is "a simple thing to do and it may protect you from some other illnesses."

But current evidence shows that influenza is transmitted primarily at a short range of one to two metres by inhaling particles from an infected person ("inhalation transmission"), although the virus can survive on surfaces and, theoretically, transmission can occur from contaminated surfaces and hands ("contact transmission"), according to the report, which was crafted in 2007 by 13 senior academic and clinical physicians, nurses and one judge from across Canada. The expert panel, which examined 128 sources of evidence, was struck by the Council of Canadian Academies in response to a request from PHAC. The council was established in 2005 with a $30 million founding grant from the government of Canada to provide independent assessments of scientific issues for governments and other bodies.

Low explains that receptors for the virus are located farther back in the respiratory tract than those for rhinoviruses (colds). It is more difficult for viral particles to reach the pharynx, trachea, bronchi and alveoli-where influenza receptors are found-from a contaminated hand touched to the mouth or nose. The particles can more readily reach the sites if they are inhaled.

"Every time you talk, laugh, cough, sneeze, you're generating particles that are coming out of your mouth that are various sizes," Low says. Large "ballistic" particles over 100 microns fall to the ground. But smaller particles ranging from 0.1 to 100 microns stay in the air from seconds to days, depending on humidity, airflow and ultraviolet light. These particles can be inhaled deeply into the respiratory tract, with smaller ones capable of reaching the tracheobronchial and alveolar tissues.

In practice, studies show the greatest risk is within one metre, Low adds. "Whether someone is infectious will vary [with] the amount of virus. There's a huge dilutional factor right away as soon as you get away from the person infected."

Surgical masks-designed to protect patients from surgeons-provide some protection against contact and inhalation transmission, but allow air in the sides and do not meet an established standard, Low explains.

N95 masks, however, do meet the test. Created to protect workers in the construction industry from breathing in particulates and widely available in hardware stores, they must meet standards set by the US National Institute for Occupational Safety and Health. They fit tightly on the face and block particles as small as 0.1 micron.

While PHAC states on its website that it does not recommend that healthy people wear masks as they go about their daily lives, Low says N95 masks have a role in protecting the public. "If you had somebody at home with influenza, wearing an N95 mask would be very appropriate."

Low also rejected PHAC's assertion that improper mask use may increase the risk of infection. PHAC claims that "masks do not act as an effective barrier against disease when they are worn for extended periods of time. In addition, removing your mask incorrectly can spread virus to your hands and face."

Low dismisses as unfounded concerns that were expressed during the severe acute respiratory syndrome outbreak that N95 masks could be compromised by extended wearing (more than 4 hours), handling or a heavy virus burden. "These are very well-made masks."

The Council of Canadian Academies report found that there are no studies on handling of used masks. The few studies of particle release from filters indicated that the release was insignificant and "unlikely to be of concern," Canada's Chief Public Health Officer, Dr. David Butler-Jones, states on PHAC's website, though, that it can be easy to get a false sense of security from wearing the mask."

Low counters: "I don't know where the false sense of security would come from."

PHAC currently disagrees with using N95 masks except in very specific circumstances. "For example, we only recommend the use of N-95s for healthcare workers who are doing aerosol-generating procedures (like intubation). This kind of procedure would only be done in a health care setting. For home care, we recommend that the sick person wear a mask if possible, and if the sick person cannot tolerate it, the caregiver may choose to wear a mask when in close contact with the sick person," the agency stated in an email.

The agency's Infection Control Expert Advisory Working Group, though, is now reviewing evidence about the efficacy of N95 masks.

PHAC also indicated that its public recommendations were developed "by reviewing current scientific evidence and working with public health experts in infection control and infectious diseases." It used the Council of Canadian Academies report on respiratory equipment in its recommendations for health care workers, contained in the Infection Control Annex of the Canadian Pandemic Plan.

(hat tip Avian Flu Diary)

[WalkieTalkie, RN]

I don't know if hand washing will help me from getting swine flu or not, but I couldn't wait to wash my hands after shopping at Wal-Mart tonight! Ick!

[november17, ASN, RN]

phew I guess I can stop washing my hands so much!

[surviveslu]

It is important for us ro perform handwashing after we see a patient before seeing another patient in another room. This is an effort to prevent nosocomial infection, right? So, let me raise this question about blood pressure cuffs -- why it is okay that we use the same blood pressure cuff for most patients on the floor??? Is there any risks, not proven yet, for nosocomial infection here?

[indigo girl]

It is important for us ro perform handwashing after we see a patient before seeing another patient in another room. This is an effort to prevent nosocomial infection, right? So, let me raise this question about blood pressure cuffs -- why it is okay that we use the same blood pressure cuff for most patients on the floor??? Is there any risks, not proven yet, for nosocomial infection here?

It really is not OK to use the same cuff without cleaning them between patients as per the policy at our facility.

We use disposable cuffs on my unit. They are used for more than one patient but between each use, they are cleansed with Cavicide.

And, since this thread is on handwashing and transmission of influenza, I want to point out that the latest research indicates that swine flu may be transmitted through the conjunctiva of the eyes so handwashing is important as are goggles and face shields to protect against novel H1N1.

http://ajp.amjpathol.org/cgi/content/abstract/ajpath.2010.091087v1

...pandemic H1N1pdm virus differs from seasonal H1N1 influenza virus in its ability to replicate in human conjunctiva, suggesting subtle differences in its receptor-binding profile and highlighting the potential role of the conjunctiva as an additional route of infection with H1N1pdm.

[november17, ASN, RN]

It is important for us ro perform handwashing after we see a patient before seeing another patient in another room. This is an effort to prevent nosocomial infection, right? So, let me raise this question about blood pressure cuffs -- why it is okay that we use the same blood pressure cuff for most patients on the floor??? Is there any risks, not proven yet, for nosocomial infection here?

You've got a good point. I work at two hospitals.

#1 - Each patient is given a BP cuff on admission. It is disposable. It stays in their room and is only used on them.

#2 - The BP cuffs go from room to room unless a patient is on precautions. then we do everything manually with equipment that is disposable and left in their room and thrown away when they go.

[oramar]

I have been wondering about this, have been hearing something to this effect but this is the most up to date info to this point.