[Question #1104] HBV household transmission (razor, toothbrush etc?)

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93 months ago

Dear Drs. Handsfield & Hook,


First of all many thanks in advance for taking my question, I understand you are both leading experts in the field and have taken much comfort from your answers here and on Medhelp. My question relates to household transmission of HIV, Hepatitis B & C, primarily by razors and toothbrushes. To give some background, I've had a couple of Asian girlfriends (Thai and Chinese-born) who've each lived with me, my parents and siblings for 1-2 months (I didn't have my own place at these respective times).


I know at least one of my gfs would frequently use my razor and toothbrush. We have a single shared bathroom in my house, so my great fear is my ex-gfs who come from a country where the above diseases are rampant (particularly HBV) may have used a razor/toothbrush belonging to my parents/siblings.


I took great comfort in your Medhelp post here - http://www.medhelp.org/posts/HIV---Prevention/Merry-Christmas-Shared-Listerine/show/2065755, which stated that the risks were extremely low and theoretical. Also I have been tested and have no STDs myself.


However since then I've read a number of studies by reputable (western) institutions in medical literature (and on CDC website) stating there is a significant risk for household transmission in the case of HBV, which really scares me. So my questions are:


- How is this possible if transmission via razors, toothbrushes, towels etc is so low?

- Also if the risks from razors, toothbrushes, towels are so low, why do so many studies state it is common for infants/young children to be infected (when they were not infected at birth?)

- Would it be possible to get an approximate idea of the risks here? Ie are the risks of sharing a razor/tootbrush with an HBV-infected person likely to be 1 in 1000, 1 in 10,000 or higher (per use of shared shaver?)


Sorry I don't mean to seem like I'm questioning your expertise, I'm just trying to reconcile the advice on Medhelp etc. with medical studies and advice from the CDC.


Speaking to my entire family and asking for them to all be tested because of people I brought into our family home is not an option unfortunately. Also I’m no longer in touch with my ex-girlfriends to ask them to be tested.


Many thanks again.


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Edward W. Hook M.D.
93 months ago

Welcome to our Forum.  You ask a good, logical question related to the information found on reputable sites such as those of the CDC (I will not comment on other "information", to use the term loosely, found on the internet) and the information we provide here.  There are several elements to the answer that I will provide- please consider them each.

First, there is the issue of information provided on a website designed to provide information to the general public on an official, governmentally funded web site vs. our ability to provide more individualized information which considers specific context and other information.  In contrast, as a result of direct exchange of information with clients to this site, we are able to provide a more personalized information.  On the other hand, sites like those of the CDC do not have this degree of specificity.

Second is the matter of what is meant by the term "significant".  If risks goes from nearly non-detectable to 1 or 2%, then this is a significant increase, both in statistical and contextual terms but the risk is still rather low.  When we provide information to persons on this site, we are providing data directly to and for an single situation and person.  Thus we may sometimes be using the terms differently.  Further, the official sites such as the CDC much consider theoretical risks in way s that we may not (see below when I comment on your specific situation) - for instance, while I suppose it is theoretically possible, I know of no instances in which hepatitis B or C has been transmitted by saliva or kissing. 

Finally, to drill down on your situation, I would not worry.  I do not know your specific situation but assuming that you are writing from the U.S., I would say that your risk is quite low here are some of the reasons why I say this:

1.  While hepatitis B (in particular is more common in Asian nations, the majority of people still do not have it and you do not know what your prior GFs were infected.

2.  For you and your family, virtually all Americans under age 25, as well as a substantial proportion of those who are older are protected from hepatitis B by vaccination which is widespread.

3.  While spread of hepatitis B and perhaps hepatitis C through shared razors or toothbrushes is documented, it is not common and not nearly so common as the sharing of razors and toothbrushes is. Thus, while we have no studies to help us quantify the magnitude of risk, most experts thing that the risk is rather low and when it occurs involved complicating things such as unintentional transfer of blood and secretions on shared instruments.  I think it is safe to say that the risk of infection from the sort of razor or toothbrush sharing you describe, IF YOUR GF WAS INFECTED, is less than a 1%.   Further, presuming that your own contact with your prior GFs was far closer than that of other family members, the fact that you are not infected makes it unlikely that other family members were as well.

For all of these reasons, and given that you do not feel you can suggest to your family that they all be tested (FYI, I do not think this is necessary anyway), I would not be worried if I were you.  That is not to say that not sharing razors or toothbrushes is not a good idea, it is something to avoid but I would not spend a lot of time worrying about these past events going forward.  I hope my comments and perspective are helpful to you.  EWH

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93 months ago
Dear Dr. Hook,

Thank you so much for coming back so quickly with a very informative response. I have a couple of follow-up questions on your points (apologies but this has been a major source of stress and anxiety for me over the past few days) -

2. I live in a (Western European) country which does not have an HBV immunisation program like in the US. Therefore myself and my family have not been vaccinated against HBV, would this change your opinion in any way?

3a) Just to check, is the <1% risk per each gf's stay (i.e. sharing razors over 1-2 months, assuming they were both infected), or <1% per single exposure to a shared razor?  (I think you mean the former, but just want to double-check)

3b) I realise the data on razors/toothbrush transmission is limited so an exact figure is not possible, but would it be correct to say the above-mentioned <1% risk is in fact closer to 0.1% (or lower) than 1% (for both razors and toothbrushes?) I base this on the fact that Dr Handsfield stated both razor & toothbrush transmission are essentially theoretical with limited or no documented cases. And I remember yourself on Medhelp saying there had been no cases in the US of proven HBV transmission via barbershops - so these must be rare occurences?
So is <1% a relatively conservative figure, and <0.1% more likely? (In my mind there is a substantial difference in terms of risk to my family)

Many thanks again Dr,

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Edward W. Hook M.D.
93 months ago

2.  Sorry to hear that you have not been vaccinated but this still would not change my assessment.

3a.  This is apparently a theoretical question.  My estimate would be less than 1% overall although obviously, the more exposures there are the higher the risk.

3b.  Yes, my 1% estimate is conservative and the true risk could certainly be far lower.  EWH

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93 months ago
Dr. Hook,

Many thanks again for taking the time to respond, what you've said so far really helped to reassure me (this has been a major source of anxiety for me, thinking I have inadvertently put my family at risk). I just have a few more questions:

1. Just to check, if towels were shared regularly over 1-2 months would it be correct to assume this would be at most the same level of risk (but likely lower) as razors or toothbrushes? And does this apply for other forms of non-sexual household contact (sharing bed linen, clothes etc) - i.e. it would be no riskier than the sharing of razors and toothbrushes (so again the risk of infection <1% per each gf's stay?)

2. Am I correct that the risk of syphillis household transmission via razors, toothbrushes, towels etc (assuming my gfs were infected), would be at most the same or less than HBV? (i.e. the risk of infection <1% per each gf's stay?)

3. I understand what you said about the CDC, that definitely makes sense. However looking here - http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5708a1.htm - they cite studies where 14-60% of people living with HBV-infected people have also been infected with the virus. These percentages seem alarmingly high, and in contrast to the very low risks yourself & Dr. Handsfield mention? Looking at some of these studies, they appear to be consist of relatively small sample sizes. Is it the case then that these risks have not been borne out when expanded to a wider population? And if so, why does the CDC reference them?
Apologies I don't mean to be questioning your advice or knowledge in any way, I'm just trying to reconcile these studies with the low risks you've cited.

4. I came across a Medhelp post - http://www.medhelp.org/posts/STDs/Doctor-please-answer/show/1373645 - where Dr. Handsfield states that, although him and yourself are STD experts, he is not an expert in bloodborne transmission and does not keep up with the latest research - which was quite worrying.
So my question is - would it be fair to say that, although your main expertise is in sexual transmission, your knowledge as an epidemiologist and your general expertise with these diseases still makes you an expert in the context of answering these questions? (i.e. bloodborne/household transmission). I would assume as an epidemiologist you would also keep up with research on bloodborne transmission for HIV, HBV, HCV, syphillis etc?

Again I'm extremely grateful for all your help, and if any of my questions come off as questioning you I again apologise. I'm just desperately trying to understand all of this from a layman's perspective. Many thanks again.

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Edward W. Hook M.D.
93 months ago

1. If anything towels, bed linen, etc.   would be lower risk than sharp objects like razors or toothbrushes.

2.  Correct.  There are no cases of syphilis transmission in this way that I have ever heard of.

2.  Small sample sizes, sexual partners living with infected persons account for this.

4.  I feel entirely comfortable with the information and advice that I have provided.,

This is my third reply to your questions.  As per form guidelines, now, after three answers, this thread will be closed later today.  EWH