Aa
efficiency of HIV transmission by different fluids
Hi doc. I've been reading your forum for a week while waiting for HIV test results this Friday.
I have a general question about transmission. I hope you do not delete it.
While I have no doubt that a complete explanation would be too big for this forum, is there any way, from your perspective, why some fluids are more "efficient" than others at transmission?
Why does concentration matter? Why are the odds so important? Why do you frequently say
exposure generally happens after repeated encounters, as opposed to one?
Why is concentration of HIV so important? Why does it not take just one virus?
The other forum person told me, as you did, that I was not at risk from saliva exposure, even if I had open mouth wounds. The hypothetical ( not necessarily real) existence of semen ( who would ever see it?) in saliva did not impress the other forum answer-person. You also say kissing is not a risk,
and I have to believe that's with the possible presence of blood in mind. One of your past threads
said "everyone has cuts or sores in their mouth from time to time."
I am just trying to understand so I don't scare myself if anything ever comes up in the near, or distant future. I do have a bachelor's and masters in biology. This does not make me an MD or a virologist, but I can understand explanations up to a certain point.
Thank you very, very much.
I have a general question about transmission. I hope you do not delete it.
While I have no doubt that a complete explanation would be too big for this forum, is there any way, from your perspective, why some fluids are more "efficient" than others at transmission?
Why does concentration matter? Why are the odds so important? Why do you frequently say
exposure generally happens after repeated encounters, as opposed to one?
Why is concentration of HIV so important? Why does it not take just one virus?
The other forum person told me, as you did, that I was not at risk from saliva exposure, even if I had open mouth wounds. The hypothetical ( not necessarily real) existence of semen ( who would ever see it?) in saliva did not impress the other forum answer-person. You also say kissing is not a risk,
and I have to believe that's with the possible presence of blood in mind. One of your past threads
said "everyone has cuts or sores in their mouth from time to time."
I am just trying to understand so I don't scare myself if anything ever comes up in the near, or distant future. I do have a bachelor's and masters in biology. This does not make me an MD or a virologist, but I can understand explanations up to a certain point.
Thank you very, very much.
MEDICAL PROFESSIONAL
Thanks for the thanks. Best wishes.
I will contribute to the U of M medical HIV clinic after reading your enlightening reply. Also, thanks for helping me.
It has been stated numerous times that HIV is not found in saliva and not one case has ever been documented by kissing!
A few days ago I engaged -- for two - three nights in a row some kissing with the same woman. I had a recently developed (before any kissing was done) a cold sore on my bottom lip. The woman I was kissing -- a white, 20 year old college student -- told me later revealed she has had sex with only 2 people. (I didnt ask her if she has ever been tested for STDS HIV; she said she has kissed 25 for whatever that is worth)
The first night I was drunk and am unsure of how much kissing was actually done but I imagine some french kissing. The next day and following night not much kissing was done because of my cold sore, just light kissing.
My concern is the following: While her HIV status is unknown, what are the chances HIV could have been transmitted from kissing her through my open-cold sore?
Really, I just want to know if I need to get an HIV test or if I can forget about it.
Thanks for your wonderful service.
The first night I was drunk and am unsure of how much kissing was actually done but I imagine some french kissing. The next day and following night not much kissing was done because of my cold sore, just light kissing.
My concern is the following: While her HIV status is unknown, what are the chances HIV could have been transmitted from kissing her through my open-cold sore?
Really, I just want to know if I need to get an HIV test or if I can forget about it.
Thanks for your wonderful service.
Doc, you wrote:
Herpes lesions are loaded with CD4 cells, thus the importance of genital herpes in increasing the HIV transmission rate if exposed;
Wouldnt that mean that kissing with an open herpes sore would be a substantial risk?
Herpes lesions are loaded with CD4 cells, thus the importance of genital herpes in increasing the HIV transmission rate if exposed;
Wouldnt that mean that kissing with an open herpes sore would be a substantial risk?
MEDICAL PROFESSIONAL
The American Foundation for AIDS Research (AMFAR). Or contact the nearest large university and learn if it has a charitable donation that accepts contributions for HIV/AIDS research.
Not dwelling here. Just forgot to ask you if there are any particular HIV research foundations, etc, that you feel are particularly worthy of donated money.
If it is unprofessional for you to mention any certain groups here, I understand. Just giving it a shot.
If it is unprofessional for you to mention any certain groups here, I understand. Just giving it a shot.
I would like to thank the forum M.D.for giving this on-time substancial info on how hiv can and cannot be transmitted. for the first time someone explains why people with herpes become more likely to get inffected. and not only that, a lot of things were thrown into light for me after reading this, thank you so much Doctor.
MEDICAL PROFESSIONAL
Maybe you saw the label showing the type of blood tube. A commonly used one is whole blood EDTA. In any case, disregard what specific HIV test was done. Rely on the provider who did it. If he said you don't need to be worried about HIV, take his and my reassurance and stop dwelling on this.
Just thought I'd put it out there that I got my 4 week test back, and as you expected,
I'm negative.
The man at the testing center said that enough time had passed that I don't need to
be worried about HIV anymore. I should have gotten a more specific name for the test, but I recall it looking like Whole Blood Count EDTC or something; not ELISA.
Thank you for your patience...um..with your patients!!!
I will donate money to HIV studies and prevention!!!!!
I'm negative.
The man at the testing center said that enough time had passed that I don't need to
be worried about HIV anymore. I should have gotten a more specific name for the test, but I recall it looking like Whole Blood Count EDTC or something; not ELISA.
Thank you for your patience...um..with your patients!!!
I will donate money to HIV studies and prevention!!!!!
MEDICAL PROFESSIONAL
"Vaginal" fluid really is cervical, and in itself is a source of HIV transmission. Trauma probably increases the risk of HIV transmission, but that risk is to the woman if the man is infected; it probably doesn't bring much increased risk to the male. Such trauma is uncommon in vaginal sex, except perhaps in sexual assault.
Doctor Is vaginal fluid very infectious or is it a possibility that alot of penal vaginal exposures that result in hiv infection is beacause the physical act of vaginal sex can tear or inflame the interior of the vagina possibly adding blood to vaginal secretions?
This is some good reading for you and others on this site with questions about testing times. Would you beable to add something to this? this was posted by someone in the support forum
The question of windows period post-exposure is one of the most common ones on these boards. I've spent some time doing investigation. I am a scientist by trade, although not a biologist nor medical doctor.
The first thing that struck me is the lack of recent studies to reaffirm the current guidelines of 13 weeks. Especially as tests have improved over time. I've found only one well-written study and it is this one (published: 2000)
http://www.aidsonline.com/pt/re/aids/fulltext.00002030-200010200-00014.htm;jsessionid=GpvJP3Q2p2xvCGsVJg2yylpMDpM5nV62XVcl0zWMchp922jmlCKF!-756477024!181195629!8091!-1
What they did is used a series of blood draws from people that would turn out to be HIV infected, and ran them against a set of HIV tests. They used modern tests of the time (1997) as well as data from tests in 1987. A few interesting observations:
1) Of people they could pinpoint to a single exposure, they all showed symptoms in four weeks. 87% showed symptoms in first 15 days.
2) The antibody tests in 1987 were a LOT less sensitive. The most sensitive 1987 antibody test detected all positive samples by ~26 days after first *symptoms* appeared. And the average 1987 antibody test was closer to ~36 days after first symptoms.
If you add 15 (time for first symptoms) +36 this puts you to about 51 days post-exposure before there was high confidence that you could detect antibodies. This probably explains the 13 week guidance.
3) The antibody tests in 1997 were much more sensitive! Note, even first generation tests were drastically improved:
"By the 1987 Abbott first-generation test, employing cell-lysate antigens, 99% of seroconversions were estimated to occur within 48/78 (early/late) days. The improved 1997 Abbott first-generation test detected seroconversion significantly earlier with 99% estimated within 16/20 days."
The first generation tests removed 32/58 days from the window. That's about a 5-8 week reduction!
4) The worst 1997 test detected antibodies at about 20 days from first symptoms, and most did so at ~14 days.
If you add 15 + 14 = 29. Thus at about 29 days post-exposure most of the modern tests (even 1st generation) will have pretty high confidence. If you factor in the person who had first symptoms at 28 days: 28 + 14 = 42 days (6 weeks).
The upshot is that 13 weeks is still the holy grail. You never got fired for buying IBM (back in the day), likewise no one can dispute a 13 week window recommendation. But there does seem to be strong evidence that 4-6 weeks is exceptionally encouraging with modern tests.
The question of windows period post-exposure is one of the most common ones on these boards. I've spent some time doing investigation. I am a scientist by trade, although not a biologist nor medical doctor.
The first thing that struck me is the lack of recent studies to reaffirm the current guidelines of 13 weeks. Especially as tests have improved over time. I've found only one well-written study and it is this one (published: 2000)
http://www.aidsonline.com/pt/re/aids/fulltext.00002030-200010200-00014.htm;jsessionid=GpvJP3Q2p2xvCGsVJg2yylpMDpM5nV62XVcl0zWMchp922jmlCKF!-756477024!181195629!8091!-1
What they did is used a series of blood draws from people that would turn out to be HIV infected, and ran them against a set of HIV tests. They used modern tests of the time (1997) as well as data from tests in 1987. A few interesting observations:
1) Of people they could pinpoint to a single exposure, they all showed symptoms in four weeks. 87% showed symptoms in first 15 days.
2) The antibody tests in 1987 were a LOT less sensitive. The most sensitive 1987 antibody test detected all positive samples by ~26 days after first *symptoms* appeared. And the average 1987 antibody test was closer to ~36 days after first symptoms.
If you add 15 (time for first symptoms) +36 this puts you to about 51 days post-exposure before there was high confidence that you could detect antibodies. This probably explains the 13 week guidance.
3) The antibody tests in 1997 were much more sensitive! Note, even first generation tests were drastically improved:
"By the 1987 Abbott first-generation test, employing cell-lysate antigens, 99% of seroconversions were estimated to occur within 48/78 (early/late) days. The improved 1997 Abbott first-generation test detected seroconversion significantly earlier with 99% estimated within 16/20 days."
The first generation tests removed 32/58 days from the window. That's about a 5-8 week reduction!
4) The worst 1997 test detected antibodies at about 20 days from first symptoms, and most did so at ~14 days.
If you add 15 + 14 = 29. Thus at about 29 days post-exposure most of the modern tests (even 1st generation) will have pretty high confidence. If you factor in the person who had first symptoms at 28 days: 28 + 14 = 42 days (6 weeks).
The upshot is that 13 weeks is still the holy grail. You never got fired for buying IBM (back in the day), likewise no one can dispute a 13 week window recommendation. But there does seem to be strong evidence that 4-6 weeks is exceptionally encouraging with modern tests.
Now THAT'S a medical answer, and an educational one! Thank you! I admit I was picking apart your answers during different threads at first. I saw you say saliva doesn't carry ANY virus, which I didn't think was technically true, but is enough to calm most people's fears... I would hope anyway.
My area was more environmental issues and conservation, but I had to take all sorts of classes and read lots of science papers, so I can pick this apart. I DO also understand you have a certain perspective you try to get across. Thank you very much for answering and not deleting.
I have been trying to get into writing as a new career move, and medical writing is one thing of interest of mine. If a pitch of my own was accepted on this subject, I would be honored if some day I could interview you or have you be a resource.
I'll also be sure to donate to HIV research. Thank you and have a wonderful day!
My area was more environmental issues and conservation, but I had to take all sorts of classes and read lots of science papers, so I can pick this apart. I DO also understand you have a certain perspective you try to get across. Thank you very much for answering and not deleting.
I have been trying to get into writing as a new career move, and medical writing is one thing of interest of mine. If a pitch of my own was accepted on this subject, I would be honored if some day I could interview you or have you be a resource.
I'll also be sure to donate to HIV research. Thank you and have a wonderful day!
MEDICAL PROFESSIONAL
All infectious diseases have exposure thresholds. It takes a very small exposure, maybe "only one virus", to infect someone with rabies, but that is the rare exception. For two common gastrointestinal infections, the range is very broad. In human volunteer studies, the dose of swallowed Shigella (the cause of bacterial dystentery) that establishes infection in 50% of the volunteers (called the ID50) is around 50 bacteria. For Salmonella, a common cause of food poisoning, the ID50 is 50,000 bacteria, 1000x more than for shigella.
To my knowledge, there are no data on the ID50 for HIV, and it would vary by exposure route. It takes less virus to cause infection if the virus is mainlined, as by blood transfusion, than through sex. There are all kinds of natural barriers, immune cells that kill invaders before they have a chance to attach to susceptible cells (CD4 lymphocytes, Langerhans cells, others). The number of CD4s in, say, a skin wound might be lower in one cirucmstance than another. Herpes lesions are loaded with CD4 cells, thus the importance of genital herpes in increasing the HIV transmission rate if exposed; whereas a cut from injury may not have many such cells near the surface. And on and on.
Connected with that, the amount of virus in various body secretions varies widely. It is higher in blood than semen, which in turn is more than in saliva (almost zero) or breast milk (very low). No HIV appears in sweat. And so on.
The major take home message is for persons concerned about risk of catching HIV to forget the biology and rely on the epidemiology. We know that nobody has ever been proved to have acquired HIV by kissing, for example; to my knowledge, even a suspected case has never been reported. Given how common sores in and around the mouth are, and the frequency with which people have inflamed gums, it is obvious those things don't make much difference. When HIV-discordant mongamous couples have sex on a regular basis, the average transmission rate is around once per 1000-2000 episodes of unprotected vaginal sex. Kissing is zero risk, period. Can I imagine a scenario in which kissing or oral exposure to an open sore might result in HIV transmission? Of course. I can also imagine being hit by a meteorite.
"Why are the odds important?" Because they make all the difference in the world. Shoot heroin with a needle just used by a person you learn is HIV positive? Run, do not walk, to the nearest provider of post-exposure prophylaxis. Have condom protected sex with co-worker whom you have no reason to suspect is bisexual or an injection drug user? Use your seat belt--because dying in an auto accident in the coming week has a far greater chance of killing you than HIV.
So take heart in the data about the non-occurrence (or extreme rarity) of HIV in people who have such exposures as kissing, household contact, oral sex, lap dances, and protected vaginal or anal sex. There is no reason to doubt those data, and you can twist yourself in knots if you try to factor in the biology behind it. There is no point in it.
Tons have been written about all this. With your biology experience, you should have no trouble accessing the scientific literature for much more detailed biological explanations than I can give.
Regards-- HHH, MD
To my knowledge, there are no data on the ID50 for HIV, and it would vary by exposure route. It takes less virus to cause infection if the virus is mainlined, as by blood transfusion, than through sex. There are all kinds of natural barriers, immune cells that kill invaders before they have a chance to attach to susceptible cells (CD4 lymphocytes, Langerhans cells, others). The number of CD4s in, say, a skin wound might be lower in one cirucmstance than another. Herpes lesions are loaded with CD4 cells, thus the importance of genital herpes in increasing the HIV transmission rate if exposed; whereas a cut from injury may not have many such cells near the surface. And on and on.
Connected with that, the amount of virus in various body secretions varies widely. It is higher in blood than semen, which in turn is more than in saliva (almost zero) or breast milk (very low). No HIV appears in sweat. And so on.
The major take home message is for persons concerned about risk of catching HIV to forget the biology and rely on the epidemiology. We know that nobody has ever been proved to have acquired HIV by kissing, for example; to my knowledge, even a suspected case has never been reported. Given how common sores in and around the mouth are, and the frequency with which people have inflamed gums, it is obvious those things don't make much difference. When HIV-discordant mongamous couples have sex on a regular basis, the average transmission rate is around once per 1000-2000 episodes of unprotected vaginal sex. Kissing is zero risk, period. Can I imagine a scenario in which kissing or oral exposure to an open sore might result in HIV transmission? Of course. I can also imagine being hit by a meteorite.
"Why are the odds important?" Because they make all the difference in the world. Shoot heroin with a needle just used by a person you learn is HIV positive? Run, do not walk, to the nearest provider of post-exposure prophylaxis. Have condom protected sex with co-worker whom you have no reason to suspect is bisexual or an injection drug user? Use your seat belt--because dying in an auto accident in the coming week has a far greater chance of killing you than HIV.
So take heart in the data about the non-occurrence (or extreme rarity) of HIV in people who have such exposures as kissing, household contact, oral sex, lap dances, and protected vaginal or anal sex. There is no reason to doubt those data, and you can twist yourself in knots if you try to factor in the biology behind it. There is no point in it.
Tons have been written about all this. With your biology experience, you should have no trouble accessing the scientific literature for much more detailed biological explanations than I can give.
Regards-- HHH, MD
You are reading content posted in the HIV - Prevention Forum
Condoms are the most effective way to prevent HIV and STDs.
PrEP is used by people with high risk to prevent HIV infection.
Can I get HIV from surfaces, like toilet seats?
Can you get HIV from casual contact, like hugging?
Frequency of HIV testing depends on your risk.
Post-exposure prophylaxis (PEP) may help prevent HIV infection.
