Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

[mixin]

Conclusion: Hand hygiene and facemasks seemed to prevent household transmission of influenza virus when implemented within 36 hours of index patient symptom onset. These findings suggest that nonpharmaceutical interventions are important for mitigation of pandemic and interpandemic influenza.

Background: Few data are available about the effectiveness of nonpharmaceutical interventions, such as hand hygiene and facemasks, for preventing influenza virus transmission.

Objective: To investigate whether hand hygiene and use of facemasks prevents household transmission of influenza.

Design: Cluster randomized controlled trial. Randomization was computer generated; allocation was concealed from treating physicians and clinics and implemented by study nurses at the time of the initial household visit. Participants and personnel administering the interventions were not blinded to group assignment.

Setting: Households in Hong Kong.

Patients: 407 people presenting to outpatient clinics with influenza-like illness who were positive for influenza A or B virus by rapid testing (index patients) and 794 household members (contacts) in 259 households.

Intervention: Lifestyle education (control) (134 households), hand hygiene (136 households), or surgical facemasks plus hand hygiene (137 households) for all household members.

Measurements: Influenza virus infection in household contacts, as confirmed by reverse transcription polymerase chain reaction (RT-PCR) or diagnosed clinically after 7 days.

Results: Sixty (8%) household contacts in the 259 households had RT-PCR–confirmed influenza virus infection in the 7 days after intervention. Hand hygiene without or with facemasks seemed to reduce influenza transmission, but the differences in transmission compared with the control group were not statistically significant. In 154 households in which interventions were implemented within 36 hours of symptom onset in the index patient, transmission of RT-PCR–confirmed infection seemed to be reduced, an effect attributable to reductions in infection among participants using facemasks plus hand hygiene (adjusted odds ratio, 0.33 [95% CI, 0.13 to 0.87]). Adherence to interventions was variable.

Limitation: The delay from index patient symptom onset to intervention and variable adherence may have mitigated intervention effectiveness.

http://www.annals.org/cgi/content/short/0000605-200910060-00142v1?rss=1

 

[gsgs]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

http://www.annals.org/cgi/content/full/0000605-200910060-00142v1

http://scienceblogs.com/effectmeasure/2009/08/the_hand_washingface_mask_pape.php


2ndary attack rate for flu-contacts =
~20% of households,
~8% of people in those households


2ndary attack rate =
23% in the control group,
11% in the hand hygiene group,
and 18% in the facemask plus hand-hygiene group


http://www.annals.org/cgi/content/full/0000605-200910060-00142v1/T3


? doesn't match ... I have to check again ...

 

[Lizw]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

http://www.annals.org/cgi/content/full/0000605-200910060-00142v1

http://scienceblogs.com/effectmeasure/2009/08/the_hand_washingface_mask_pape.php

The attack rates were 24% in the control group,
14% in the hand hygiene group,
and 18% in the facemask plus hand-hygiene group

http://www.annals.org/cgi/content/full/0000605-200910060-00142v1/T3

A higher percentage of infection in the facemask PLUS hand-hygiene group? Makes you wonder if people were depending too much on the face masks and relaxing their hand-hygiene efforts. But the article said "Adherence to interventions was variable," so it could also just have been coincendental.

 

[gsgs]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

"significance" here is just a threshold to be defined.

in reality it comes in degrees, something can have more or less significance

 

[gsgs]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

with only 8% secondary attack rate in households,
I wonder how flu can maintain R0>1.

Seems to imply that most of transmission happens outside households

 

[gsgs]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

just another unclear phrase to replace the first one.

It doesn't matter so much/enough/

and again you have to define a threshold.


Often in statistics they use 95%-certainety for "significant"

 

[mixin]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

No one has to put faith in a study; nor do they have to use any kind of interventions.

Overall, the interventions did not lead to statistically significant reductions in household transmission, although we did observe statistically significant reductions where interventions were applied early after symptom onset in the index patient.

we have probably underestimated the true effectiveness of these simple interventions.

 

[gsgs]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

Lizw, yes the study tells us, that when you use
hand hygiene to prevent household transmission
then don't use masks too !

Maybe because people with masks have fewer time
for hand hygiene or can't find the soap or such.

 

[mixin]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

Maybe people feel more protected when they wear masks and forget how important washing hands is?

 

[the doctor]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

Posted today on Effective Measure

This was a hard study to do, no question about it. Can you imaging making 3 home visits to 407 families over 8 days!

While I understand why the authors decided to eliminate so many families from analysis, by doing so they fell below the number needed within each group to give the researchers a reasonable chance of showing a significant difference between interventions.

We can quibble about this but either we live by the evidence based medicine sword or we die by it. If we are going to require interventions to meet statistical significance before being widely adopted, then we need to stick with that standard.

When an underpowered study like this one is published that fails to be conclusive using the standard we apply to all other interventions, then we need to say this and conclude that there is nothing to conclude about the effectiveness of hand washing and mask wearing.

Of course the big problem with this study was getting the patients and their families to cooperate with the protocol. The authors point this out in the statement below:

"Limitation: The delay from index patient symptom onset to intervention and variable adherence may have mitigated intervention effectiveness".

It is difficult to get medical personnel to adhere to tight infection control protocols, so I can imagine how difficult it is to get everyday people to do so and do it well.

The latency in the time from when the index case became symptomatic and the interventions were implemented was the major problem with this study and why it probably failed to show significant benefit. Since an index adult case begins shedding virus about 48 hours before becoming symptomatic and for several days afterward, even if the first home visit occurred 36 hours after the patient's first clinic visit, the family would have been exposed for 3.5 days to the contagious sick person without the benefit of the intervention.

The statistically significant reduction in relative risk for secondary infections within the family for those who began the intervention within 36 hours of the index patients initial visit then was surprising; in fact unexpected. So unexpected that this result could have been due to chance alone, a problem seen in underpowered studies with unexpected outcomes.

However, this study is already being ballyhooed in the media and will be a cause celeb for a while despite its limitations. TPTB will point to it with enthusiasm and in the end will use it to reassure the public that PAN-flu can be defeated by HYGEIA.

During pandemic conditions for the vast majority of families with an index patient, there will be no initial clinic visit, no home nurse visits, no masks, no alcohol based waterless hand cleaner. Their might be PSAs, gossip, rumors, and old wives tails but not much else.

The circumstances that the intervention reported upon in this thread then are totally artificial and so unlike what the real world conditions would be like and even then, they failed to be effective.

Grattan Woodson, MD

Posted by: The Doctor | August 5, 2009 8:15 AM
2

Gratt: Statistical significance is an artificial convention meant to provide some information about one of the things that influences outcomes (random variation). It should never be used as you suggest, as a bright line. That leads to ignoring information of public health significance and giving prominence to information that may be of no public health significance. This paper presents some of the very few data points in the literature on an important topic and the question is how we interpret them, which is what the post was about. Note that by your criterion, the statistically significant findings for the 36 hour intervention would seal the case as being useful, but of course it doesn't. There is much else to consider. The important thing is that a scientific question was posed and an attempt to answer it with a reasonable study design whose power might have been sufficient given the size of the effect. That the real world intervenes is a given. Study designs are just designs. You still hve to carry them out and that's a difficult thing to do. I am a skeptic about handwashing and certainly about masks, but I do look at data when it's relevant, and these data are relevant and suggest some efficacy. The question about whether the study circumstances are unrealistic for the reasons you gave is totally separate and not relevant to the scientific question.

Posted by: revere | August 5, 2009 8:46 AM

Thanks for your response Revere.

Let me tell you how much I appreciate your bringing these interesting topics to the Internet everyday for discussion. This is an immense burden that some may not appreciate. Of course some may say this is what they pay you the "big bucks" for but you and I know there are no big bucks rather you all do what you do from the goodness of your hearts. You are acting in the interest of informing the public and for no other reason and for this, we all owe you a significant debt of gratitude.

It takes a great deal of effort to search the news and literature to simply find an event or article to comment on but then to find the jewels within the dustbin and make them into a cogent assessment is where you and all the Reveres shine. Thank you very much.

Please understand that in my opinion, what you Reveres are doing is the heavy lifting and what I as someone who posts here is doing, especially when I take a position in opposition to the editorial content of your efforts should be seen as the light lifting. It is very difficult to create a great Internet site with multiple daily content but very simple to offer criticism.

Again, thanks for establishing a frame of debate on pandemic influenza, on a daily basis that provides all your readers with a focus, one that informs and challenges us.

OK, enough with the praise, here comes the thorns.

If there is any benefit in the application of hand washing and use of face masks by the family with a member ill with flu, it is pretty clear to me that these interventions must be implemented very early during the illness of the index case for them to have optimal impact. As you pointed out, the article under discussion found that the spread of flu within the family with an index case can be reduced by 66% when implemented early.

What's more these interventions must be adhered to comprehensively by as many in the family as possible during the course of the illness of the index case to ensure a positive outcome.

I think it makes sense to use gloves, masks, and air purification via UV or ion methods and plan to implement them all if required. It also seems pretty likely to me that most folks including me who implement these measures might find them effective for a while but in the end they will fail.

That though is not the point of why we should use these Non-Pharmacological Interventions (NPI)s. The point of these and all other NPIs is to slow the rate of transmission of the virus through the population. No one thinks that these or any of the other NPIs including my preferred method, social distancing most particularly early school closure has any chance at all of preventing the spread of pandemic influenza to all people given the fullness of time.

The great benefit of all NPIs is to give us more time to manage the most severe effects of the pandemic, which is an excellent reason to support them. What we want to avoid is have a tsunami of severe cases come too closely together in a way that overwhelms our medical ability to manage them whether that be within the hospital or home.

Grattan Woodson, MD

Posted by: The Doctor | August 5, 2009 4:05 PM


Gratt: First, thank you for the kind words. They mean much. As for the "thorns," I pretty much agree with what you say. The issue for me is whether there is any evidence hand washing is effective (I skeptical and even more so about masks) but the data seem to suggest they are, at least to some (unknown) extent. They also modify behavior in other ways and affect other disease agents, so that's all to the good. I also think the studies probably underestimated the effect because it was started late. If people think they work (and now there is some data to suggest it) then they can start immediately and get more effect.

Posted by: revere | August 5, 2009 4:39 PM

 

[mixin]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

If a virus can't get "in" you, it cannot infect you. What better ways do we have than washing our hands and wearing masks?

Some people swear vaccines don't work either.

 

[mixin]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

Hi,

One more example... I am rural and have visited poultry barns. These barns are highly protected. I could not enter beyond a front office and even then as I entered the office I was sprayed with disinfectant. Employees lives there are painful taking as many as 13 showers a day and just as many changes of clothes. The poultry still get sick.

Tom

They should have kept the wild birds out.

 

[gsgs]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

the article at effectmeasure is too long, no summary.

revere enjoys to point out how little we know - researchers
must be doing a bad job.

assume 20 times hand washing per day for 5 days,
each time 2 minutes = 3 hours
for a 5% reduced chance to get it.
Damage of getting it ~$1000 (?)

--> expectation value of hand washing = -$10

 

[mixin]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

The Effect Measure post was a bit confusing; most of the comments were from The doctor.

Revere: The important thing is that a scientific question was posed and an attempt to answer it with a reasonable study design whose power might have been sufficient given the size of the effect. I am a skeptic about handwashing and certainly about masks, but I do look at data when it's relevant, and these data are relevant and suggest some efficacy.

I also think the studies probably underestimated the effect because it was started late. If people think they work (and now there is some data to suggest it) then they can start immediately and get more effect.

 

[gsgs]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

you can touch many things in a row, just when you
intend to touch mouth,nose,eyes wash the hands before.

Also, 20 is just the estimated number of times (by me) that people
in the handwashing-group washed their hands in the study

although 2min is a bit much, given that they are routine-handwashers
and in a household with a washing opportunity always nearby


but the estimated benefit of handwashing is still low.
You won't "earn" much more by handwashing than by
working.


neither the authors nor revere did make this cost/benefit calculation/estimate ?!

 

[mixin]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

Hi,
At this point in time there is no benefit of practical value to hand washing within a household if one member of the household is infected with influenza.

If you have a dozen sick kids climbing all over you, coughing in your face; then yes, you will probably catch it from them no matter what you do. Your fate is sealed.

If it's a couple of adults, I could see handwashing being helpful. If you don't want to wash your hands, then at least use a tissue to wipe your eyes and keep your fingers out of your nose and mouth.

 

[Andre DuMouchel]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

It would seem that opinions do vary.

When either my wife or I get sick, the sick one sleeps in a different bed, hand washing takes place on both our parts and the other does not usually become ill.

Nurses and Doctors, when dealing with the Flu are advised to wear a mask and to wash hands, the Dentist wears a face shield and gloves.

If my wife or I get this bug, the one who is sick will sleep in another room and wear a mask and the one that is not sick will wear a mask, face shield and gloves as well as washing hands.

For the same reasons we have insurance on the house and cars, for the same reason we have fire extinguishers.

By all means, avoid these behaviors if you so choose.

In the end we act in such a way as to feel more comfortable.

 

[gsgs]

Re: Facemasks and Hand Hygiene to Prevent Influenza Transmission in Households

> This is the third in a series of polls about Americans? response
> to the H1N1 flu outbreak:
> The first survey was released May 1. The second survey
> was released May 8.

so, why don't they ask how many had ILI in the critical time ?
Or has it been done and is withheld ??
Also serology.
Also if they had the 1976 vax

they must know all this, but won't tell us.