[Question #8901] Bloodborne Viruses

38 months ago

GGreetings,

I have some questions to ask; I thank you in advance.

1. Is HSV a blood-borne virus that circulates in blood? Or is it just HIV, HBV, HCV, and Syphilis?

2. What makes blood virally less concentrated than say infected tissues or secretions? In other words, why is there a need for a large amount of blood for STIs to be transmittable especially when there are bloodborne STIs; is it the fragility of these particular STIs that circulate blood?

3. For HCV - provided that it is a blood-borne virus, virtually not transmittable during vaginal sex even if the woman is menstruating - where does this virus typically originate for a man, if it is possibly transmittable in anal sex with gay partners? I guess I am trying to conceptualize why this is possible with the potential of blood exchange in anal sex but not with vaginal sex if a woman is menstruating. Do the answers make it safe to assume that HCV is “inadvertently” transmitted among gay men during anal sex and that’s what makes HCV not an STI?

4. Are both HBV antigen and HCV antibody tests totally conclusive at 6 weeks post-exposure?

Respectfully,

Michael

Edward W. Hook M.D.

38 months ago

Welcome to our fortune. Thanks for your thoughtful questions. I’ll do my best to provide answers although, in some instances the rationale behind these answers is theoretical although it is anchored in observations made in scientific studies.

1. HSV is present, on occasion, in the blood of persons with HSV infections however, transmission occurs in virtually all instances with direct contact to an infected site rather than through exposure to infected blood. FYI, the same is true for Syphilis, unlike HIV, HCV, and HBV, which are primarily transmitted through direct exposure to the blood of infected persons.

2. This is a complex question and answers vary from infection to infection. Transmission of infection is, in part, due to the concentration of virus present at the site from which transmission occurs. For different STI‘s the amount of virus in blood may be greater or less in the amount found at the clinical sites of infection compared to concentrations in blood. In addition, a variety of factors, importantly including friction and the resulting micro abrasion may facilitate the transmission of some STI’s. Finally for some but not all STI’s the immune response of the infected person may result in larger concentrations of the infectious microorganism at sites where general lesions are present them in blood.

3. Receptive anal intercourse is a somewhat more traumatic event than insertive intercourse. As a result, during receptive rectal intercourse, an infected person may experience direct inoculation of HCV virus into tissues to facilitate transmission. Even then, Sexual transmission HCV is relatively uncommon.

4. For all practical purposes, yes.

EWH

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38 months ago

Hi and Thank you Dr. Hook for taking and answering my questions. I do have follow-up questions:

For Question 2 – last sentence, “Finally for some but not all STI’s the immune response…..where general lesions are present them in blood”

There may be larger concentrations of infectious microorganism present at sites where general lesions are present than in blood for persons with weaker immune responses? If so, can I safely conversely say, HIV and Hepatitis could be more concentrated in the blood of persons with weaker immune responses. Also, may I ask why only at sites where general lesions are present that weaker immune responses yield larger concentration of virus and not primarily mucosal sites and in secretions?

For Question 3 – sentence: “As a result, during receptive rectal intercourse…..to facilitate transmission.”

For clarity, who is the infected partner, the receiver or the inserter here? Would the rationale behind sexual transmission of HCV (rare as it is) only during rectal intercourse be the rectum being a site of infection versus other common sites for other STIs? HCV is a bloodborne virus but the only mode of sexual transmission is through anal sex, not vaginal sex even when the woman is menstruating, nor oral sex. This notion would make the most sense at my understanding level.

If I may take this a bit further; I am sure there are plenty of orgies where women receive anal sex from gay men who theoretically can be at risk of HCV since the mens’ seemingly normal sexual lifestyle is having anal sex – whether receiving or giving.

For Question 4 - You mention for practical purposes, the Hepatitis tests are conclusive at 6 weeks post-exposure; is the reason epidemiological – the absence of patients who test positive before 6 weeks?

Respectfully,

Michael

38 months ago

Apologies, I omitted my follow-up to question 1.

For Question 1 – Is the reason for HSV on occasion being in the blood of HSV infected persons but only transmissible at infected sites because of the lack of viability of this virus in blood?

Thanks.

Edward W. Hook M.D.

38 months ago

Your follow-ups, like many of your past 7 series of questions deal with complex scientific questions for which data are limited. I do find myself wondering about your interests. I would also add that it is important to remember that most exposures to infectious agents of any sort DO NOT lead to transmission of infection. Thus in addition to number of exposures, the immune status of the exposed person, the concentration of the microorganism that one is exposed to, etc. there is the fact that chance (luck) also contributes. In response:

1. Question 1. As Dr. Handsfield has mentioned in the past, many factors im[pact transmission likelihood including the quantity of the microorganism present. HSV detected in blood tends to be lower in concentration than the amount of virus present. The virus detected in the bloodstream however is presumably viable. In addition, as also previously explained, for HSV DIRECT contact, typically facilitated by friction enhances transmission likelihood.

Question 2. Your follow-up is difficult to follow. As already mentioned transmission probabilities are multifactorial. Trying to determine the relative contributions of different factors is likely to vary substantially from person to person.

Question 3. As I said above, "Receptive anal intercourse is a somewhat more traumatic event than insertive intercourse. As a result, during receptive rectal intercourse, an infected person may experience direct inoculation of HCV virus into tissues to facilitate transmission." Thus infected secretions are more likely to be introduced deep into tissue for the person receiving rectal intercourse. This thereby increases the risk for infection although, as Dr. Handsfield has told you previously, sexual acquisition of HCV from receptive rectal intercourse is a rare event.

Question 4. The vast majority of hepatitis infection become detectable well before 6 weeks have passed. Almost no persons who acquire hepatitis take more than six weeks for their infection to become detectable

EWH

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38 months ago

Hi,

If I can finish up here:

For Question 1 – Your response “HSV detected in blood tends to be lower in concentration than the amount of virus present.” - Did you mean, HSV detected in blood tends to be lower in concentration than the amount of virus present at infected sites?

So, DIRECT contact refers only to exposure among: (1) mucosal surfaces and (2) skin lesions during friction? Blood (and secretions) exposure are not considered direct contact?

For Question 2 – Apologies, the word typo “them” in the last sentence of your statement through me off a little. I also wanted to

make sure I made the right connection in thinking general lesion sites are not exclusive when talking about larger concentration of infectious microorganism due to one factor (understandably) of transmission like weaker immune response. That it applies to mucosal surfaces and secretions as well. For the most part, I grasped this section of the post. Apologies again, I unintentionally miscommunicated my concern.

For Question 3 – So all in all, given the rare occurrence of sexual transmission of HCV during anal intercourse and no other common transmission during sex, this is why technically HCV is not an STI; just a mere overstatement or urban myth (as Dr. Handsfield had once put it)?

Can I at least safely say that the rectum theoretically is the infection site HCV can be transmitted sexually?

For Question 4 – Your response also applies to antibody detection correct? In other words, antibodies for HCV are detected before 6 weeks?

Respectfully,

Michael

Edward W. Hook M.D.

38 months ago

Question 1. Yes- at infected lesions

Question 2. still difficult to follow.

Question 3. Correct

Question 4. Correct

EWH

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