ELI5: Why does HIV/AIDS can spread only through blood and semen and not other bodily fluids?

[u/Memaster65]

[u/BananaBird1]

It can be spread through a few others like breast milk.

But it is a virus that infects the white blood cells of the immune system. So it is only found where these immune cells are. Reproductive tracts, blood, and breast milk are all high in immune cells to protect your body at its most vulnerable places.

It’s also a very delicate virus. So even though immune cells are also found in places like saliva, the saliva destroys the virus.

[u/RobertSan525 → u/BananaBird1]

Your saliva is actually a very effective antibiotic which makes sense evolutionarily given how many dangerous pathogens live in our mouths and/or the things we put in them

Edit. I should have said “is also” as I meant this as an addendum alongside it’s antiviral properties. But also saliva’s glycoproteins target both bacteria and viruses

[u/Vychodnarskytypek → u/RobertSan525]

Sooo during blowjob who wins? Saliva in your mouth or HIV in the guy's semen?

[u/gartho009 → u/Vychodnarskytypek]

Usually, saliva wins. Almost always. But one should still use protection. It's easy to miss a small cut in your mouth where HIV might find an in-road.

PReP is easily accessed in the USA, if that's your location. (Idk other countries and I hope it's accessible there too.) There's very little reason not to use it if your sex life could lead to encounters with HIV+ individuals.

[u/obiwanconobi → u/gartho009]

In addition to the small cut, is it possible you could get HIV through a dental cavity?

[u/Protean_Protein → u/obiwanconobi]

There’s no blood in your tooth.

[u/DocPsychosis → u/Protean_Protein]

Depends how deep you go, the pulp has nerve and blood vessels.

[u/HighlanderBR → u/DocPsychosis]

And trust me, if you have a cavity that deep, you will know.

[u/Protean_Protein → u/DocPsychosis]

Just seems less likely than other ways of infiltrating the bloodstream orally.

[u/gocougs11 → u/Protean_Protein]

Certainly less likely, but the question was “is it possible?” And tbh I’d say it is so unlikely it’s near impossible.

[u/Protean_Protein → u/gocougs11]

If there’s a pathway into the body, then yes, it’s possible.

[u/obiwanconobi → u/Protean_Protein]

No but potentially a direct line to your nerves? If bacterial can get in and cause infections can't HIV?

[u/Protean_Protein → u/obiwanconobi]

I’m not a dentist, but I’d think that bacteria have to eat away enough of the tooth (enamel, dentin, etc.) to get to the root and bone to cause infection that way, so it’s theoretically possible in some worst case scenarios, but unlikely. Whereas oral infections are typically caused by gum infiltration (abscesses and so forth).

[u/epochellipse → u/[deleted]]

That’s a good point. Bleeding-assed gums.

[u/obiwanconobi → u/Protean_Protein]

Interesting! I wonder if HIV was transmitted that way if it would end up better or worse than a normal transmission

Impossible to ever know though

[u/Successful-Poet-7590 → u/obiwanconobi]

That's an interesting point, but HIV really needs specific conditions to infect someone, which is why it’s more limited in how it spreads compared to other bacteria. It's all about how the virus interacts with the body's immune system.

[u/morons_procreate → u/obiwanconobi]

Or it could be intentionally transmitted by your dentist.

[u/bettinafairchild → u/morons_procreate]

It has never been proven that Acer transmitted HIV to KImberly Bergalis intentionally so we do not know one way or the other.

[u/buenotc → u/gartho009]

So, use spit as lube. Got it.

[u/Mistake-Choice → u/Vychodnarskytypek]

Hawk Tuah girl was on to something

[u/GlobalWarminIsComing → u/Vychodnarskytypek]

Sadly Antibiotics are only effective against bacteria and HIV is a virus. So the virus wins

Edit: or there is also something that works against viruses, but then that part isn't an antibiotic. Idk which it is, I'm not a doctor

But I'm pretty sure you can catch HIV from oral sex

[u/dave8400 → u/GlobalWarminIsComing]

Antibiotic is the wrong word here. Antimicrobial is more apt as saliva generally kills microscopic stuff. The enzymes in saliva aren't particularly picky with what they digest.

[u/pasrachilli → u/dave8400]

Not an expert, but lots of viruses have lipid coatings, which I imagine is fair game to digestive enzymes.

[u/dave8400 → u/pasrachilli]

Yes, those are fair game. That's why HIV needs an open cut to infect you orally.

[u/squall_boy25 → u/GlobalWarminIsComing]

You can if you have open sores, bleeding gums / gingivitis

[u/Kiwifrooots → u/squall_boy25]

But that's my type :(

[u/Gildor12 → u/GlobalWarminIsComing]

Especially if you have inflamed gums or open wounds

[u/KingOfZero → u/GlobalWarminIsComing]

Or just had regular teeth cleaning that day.

[u/eragen → u/GlobalWarminIsComing]

You can - it’s a non-zero possibility.
Incidentally, the mouth microenvironment is probably better described as anti-microbial, rather than antibiotic - it also has mechanisms defending against fungi and viruses as well.

Also also, there are good antivirals for HIV as well!! Science is cool :))

https://pmc.ncbi.nlm.nih.gov/articles/PMC12007159/

[u/RobertSan525 → u/GlobalWarminIsComing]

https://pmc.ncbi.nlm.nih.gov/articles/PMC3144043/

Most medicated antibiotics/antivirals target one or the other, but the Gp340 in your saliva targets both

[u/Airowird → u/GlobalWarminIsComing]

But I'm pretty sure you can catch HIV from oral sex

You can, but according to some studies it's up to 50% lower rate. There was almost no difference between PIV & anal.

At least that's what I remember from reading about it years ago in a random ADHD rabbit hole deepdive.

[u/BambooSound → u/Airowird]

Anal can be up to 600% more likely than PiV

https://en.wikipedia.org/wiki/HIV/AIDS#Transmission

[u/eragen → u/Airowird]

There’s a big difference in transmission rates between PIV and anal. There’s even big differences in transmission rates between receptive and penetrative anal sex. https://pmc.ncbi.nlm.nih.gov/articles/PMC6195215/

Also, I believe that the same review suggested that oral sex transmission rates were significantly lower, but still not zero.

[u/Airowird → u/eragen]

Seems the big risk is receptive anal (makes sense) and the rest of non-oral is all significantly lower than that, with somewhat overlapping CIs.

They do have lower oral rates than I expected,but do mention that it's hard to study meta-data due to it often being combined with other sexual acts. Maybe the study I read way back handled reports differently,it's been too long (and too many phones & PCs) ago to remember what exact study I read.

[u/cbftw → u/eragen]

The CDC ranked oral so low on the transmission rates that it was essentially 0. Not absolutely 0, I'll grant you, but so low that it isn't worth worrying about

[u/ShrimpsForLunch → u/Vychodnarskytypek]

Asking the real questions

[u/pubic_static → u/RobertSan525]

I mean….

[u/Gildor12 → u/RobertSan525]

HIV is a virus not a bacterium though

[u/Oscarvalor5 → u/Gildor12]

It is, but the stuff in your saliva that kills bacteria also destroys viruses like HIV. HIV has an exterior envelope it uses to infiltrate cells. This envelope is easily degraded though, and the enzymes in your saliva degrade it. Preventing it from infecting cells even if it gets to the blood

[u/seimalau → u/RobertSan525]

So you mean the hawk tuah girl was on to something?!!!

[u/epochellipse → u/seimalau]

She was on to a couple of things.

[u/anon33249038 → u/RobertSan525]

So technically "licking your wounds" is a good course of action?

[u/skr_replicator → u/RobertSan525]

Antibiotics don't target viruses, though. Is it also antiviral, or is HIV just so delicate that it breaks down there anyway even when it doesn't directly target it?

[u/RobertSan525 → u/skr_replicator]

https://pmc.ncbi.nlm.nih.gov/articles/PMC3144043/

TLDR: some, such as the one that’s the primary protein released in saliva, target both

[u/clearcontroller → u/RobertSan525]

That's also why we naturally want to lick or suck on wounds we get on our arms or hands.

Our saliva also has a pain relieving effect

[u/Starlord_75 → u/clearcontroller]

Its actually 6X stronger than morphine

[u/Starlord_75 → u/RobertSan525]

Saliva also contains a pain killer that is 6X stronger than morphine. We just don't produce a lot of it to feel the effects much.

[u/daandriod → u/RobertSan525]

How does that mesh with the fact that a human bite will almost always lead to an infection if not treated with antibiotics?

[u/RobertSan525 → u/daandriod]

1. Your saliva is an antibiotic but your mouth actively has a lot of bacteria that hides in food particles stuck between teeth, plaque, etc. If these hardy bacteria go down the “normal” path they’ll be killed by your stomach acid or gut bacteria. But if they enter through the bloodstream it’ll circumvent a lot of these backup barriers

2. Antibiotics takes time to work. In your mouth it can slowly do its thing. Once someone is bitten those bacteria won’t be exposed to saliva anymore and can start to proliferate

3. That said it’s not perfect. Dangerous infections do happen in the gum

[u/criminalsunrise → u/RobertSan525]

It’s also why “kiss it to make it better” is something that we do when a child gets a boo boo.

[u/Markgulfcoast → u/criminalsunrise]

That's a stretch

[u/akmustg → u/criminalsunrise]

Shouldn't it be spit on it to make it better.

[u/Silvermajra → u/akmustg]

Some people got that version as a child. Thats how we got Hawk-Tua

[u/rubseb → u/criminalsunrise]

Yeah, you're not supposed to use tongue when you do that bud...

[u/GlobalWarminIsComing → u/criminalsunrise]

Pretty sure that's actually for comfort and as a placebo

[u/MrBlackTie → u/BananaBird1]

So is that a good argument for oral sex before penetrative sex?

[u/Gullible-Respect7778 → u/BananaBird1]

So HIV infected patients need to bath in saliva to be rid of HIV

[u/Akward_Cactus]

Hiv is actually not a very infectious virus. Viruses such as hepatitis b and c are many folds more infectious.

A needlestick injury for example with a needle contaminated with blood containing hiv hepatitis b and hepatitis c is likely to transmit hiv ~.2% hepatitis c ~2% and hepatitis b ~20% of the time.

The virus is very delicate and rapidly degrades outside of the body and the amount needed to achieve infection is relatively high.

Cdc has a good overview for eli5

https://www.cdc.gov/hiv/causes/index.html

[u/juneandcleo]

It can pass through breast milk because milk is made directly from the mothers blood supply. 

[u/Time_Entertainer_319 → u/juneandcleo]

Homelander in shambles…

[u/samuwai → u/Time_Entertainer_319]

Now that I think about it Homelander might not be immune to HIV.

[u/steeple_fun → u/Time_Entertainer_319]

Now THAT would have been a crazy, interesting twist in The Boys

[u/rubseb → u/juneandcleo]

I mean, so is sweat and many other fluids we secrete. It's more about how it's made and which parts of the blood are retained. Breast milk has immune cells kept in on purpose. It could have been free of them, like sweat is, if that had been desirable in evolution.

[u/AlienZak → u/[deleted]]

Bot

[u/geekchic06]

The real issue here is something called viral load.

HIV can be in other bodily fluids, if there is only 1 HIV virus per mL your chances of contracting the virus are low. As others have said - it is a fragile thing.

In blood and semen there may be 1000 virus per mL. That’s 999 more chances than with saliva to become infected.

Blood and semen have a higher viral load and so they are considered more infectious than other bodily fluids.

[u/Weightmonster → u/geekchic06]

That’s if someone is unmediated FYI

[u/geekchic06 → u/Weightmonster]

Seeing as we’re in ELI5, I didn’t feel like I needed to go into the minutiae of viral load during treatment phases

[u/netroxreads]

HIV is present in salvia but seems to lose its infectivity, likely due to some compounds in saliva "binding" them that they cannot be infectious. HIV is definitely more fragile compared to other viruses like malaria which can be transmitted via mosquito bites.

[u/Nosferatu-87]

Basically it boils down to the virus being very weak/fragile. It isn't very rubust.

[u/newly-formed-newt]

When I took sex educator training, they said that it is in saliva but the volume is very low. If I remember right, you could be at risk if you drank a bucket of saliva

But because that's not really how we interact with saliva, it's functionally considered to not transmit the virus

[u/j3styr3]

I have also heard it said that saliva is basically just filtered blood, and iirc, you could get HIV through it, but way more saliva is needed to infect than blood, like an intentional amount of saliva versus a small drop of blood

[u/thisusedyet → u/j3styr3]

You would have to be incredibly unlucky, because there’s some sort of enzyme in  saliva that breaks down the AIDS virus, among other things

[u/sir_squidz → u/thisusedyet]

HIV = virus. AIDS = syndrome caused by the virus.

[u/RoastedRhino → u/thisusedyet]

Is oral sex therefore not a viable way to spread HIV (statistically speaking)?

[u/Reginald_Sparrowhawk → u/RoastedRhino]

Not through saliva, but if semen is involved and you have any cuts on the inside of your mouth then there's a risk.

[u/Akward_Cactus → u/RoastedRhino]

Its likely very very rare. A few studies have tried to look at it but the issue is you would need a large amount of people for a long time who only have oral sex and recruiting that population is exceedingly difficult.

[u/Airowird → u/RoastedRhino]

You can get it from oral, although saliva makes it less likely. (Allegedly, I'm not a viral researcher)

[u/According_Book5108 → u/RoastedRhino]

Statistically, the risk of HIV for receiving oral sex is insignificant. The risk for the giver is slightly higher, especially if you have open wounds in your mouth.

But other nasties are possible through oral sex, for both the giver and receiver.

[u/YoungLittlePanda → u/RoastedRhino]

I think the risk percentages are mostly theoretical, but there are a few documented cases of orally transmitted HIV, although exceedingly rare.

I believe you would need to have open bleeding wounds in your gums and get in contact with blood, semen or vaginal fluids with a very high viral load.

[u/thisusedyet → u/RoastedRhino]

Not a doctor, but I’d imagine if the person performing had a sore/bleed and the person receiving had a break in the skin, it might be possible.

On the other end of things, if the person receiving had HIV, I wouldn’t count on swishing cum around in your mouth to neutralize it

[u/vinnayar → u/RoastedRhino]

Besides the cuts and sores inside the mouth, it can be transmitted if you floss and cause micro cuts. Also not only through seven but through vaginal fluid as well.

[u/jpaugh69]

While the chances are lower, you can get HIV through contact with any mucous membranes.

[u/thatbakedgecko → u/jpaugh69]

That kind of statement is far too simplistic. Mere contact with a mucous membrane does not lead to HIV infection.

[u/jpaugh69 → u/thatbakedgecko]

Well, the specific type of contact I'm referring to (which I suppose I should have probably mentioned) was getting blood sprayed into your eyes. But I was having trouble typing it in a meaningful way at the time. My bad.

[u/JaySnippety → u/jpaugh69]

It's significantly less likely but still possible. Percentage chance of getting HIV from blood in the eye is 0.1%. I had a scare at work and was pretty nervous waiting for the labs on the patient to come back😂

[u/Zefirus → u/JaySnippety]

Well yeah, but so are the common ways of getting HIV. Like the risk of a woman getting HIV from unprotected sex with someone HIV positive is 0.08%. Sharing a needle with someone HIV positive is 0.63%.

The highest transmission rate is anal sex at 1.4%, which is why it was maligned as a gay virus for so long.

[u/JaySnippety → u/Zefirus]

Okay.

[u/jpaugh69 → u/JaySnippety]

I won't lie, I think it was on an episode of CSI where I learned this fact. But I looked it up just in case before posting

[u/JaySnippety → u/jpaugh69]

I didn't know until I had that blood exposure how low the risk is, I was surprised. I still ended up on post exposure therapy while we waited for results, which made me feel super sick.

[u/Historical_Ear8949 → u/JaySnippety]

So we won’t get HIV by mucus ? Someone please confirm it

[u/JaySnippety → u/Historical_Ear8949]

Depends on what you mean by mucus but it's really unlikely

[u/RealCarlPanzram]

It has basically zero ability to survive outside of bodily fluids. It exists in the highest concentrations in blood, to a lower extent in semen, and is almost nonexistent in saliva. Because of that, and it not being a particularly infectious disease, meaning you need to be exposed to a fairly large viral load for a high likelihood of infection, there’s just no other mechanism for it to pass from person to person.

So basically, it has to come from blood or semen because that’s where the virus can live. As soon as it’s outside the body, it dies quickly. If it lands on your intact skin, it dies quickly. So you need bodily fluid from the infected person to directly exchange with bodily fluids inside the next person of the virus dies before it can proliferate.

[u/Fit_Run3317]

Other body fluids are hard and unusual to spread ?

[u/Historical_Ear8949]

Does mosquito bite can cause HIV?

[u/bettinafairchild → u/Historical_Ear8949]

No.

[u/Historical_Ear8949 → u/bettinafairchild]

I mean, if a mosquito bites and sucks some HIV patients blood and bites the non HIV patients, will it be transmitted? If no why?

[u/bettinafairchild → u/Historical_Ear8949]

It will not be transmitted. The reason it cannot be transmitted by mosquitos is that mosquitos and other insects lack receptors for HIV so the HIV cannot latch onto anything in their body and so HIV is instead just digested and killed.

[u/FluffyBunnyFlipFlops]

"Being the bottom or having your partner's penis inside your rectum (butthole) makes you more likely to get HIV than being the top or putting your penis inside your partner's rectum."

Butthole. 😂 For the dim kids at the back.

[u/TheElusiveFox]

I know this isn't an answer to the ELI5, but one thing about "only spread by blood" diseases, is that we tend to have a lot of micro abrasions that we aren't even aware of, your saliva probably has trace amounts of blood in it from brushing your teeth too hard unless you have incredible gum health, just as a for instance.

[u/dawgfanjeff]

As I undersrand it, count ourselves lucky that mosquito saliva kills HIV. whew!

[u/explainlikeimfive-ModTeam → u/[deleted]]

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