It is known that HIV is usually transmitted by direct blood or body fluid contact between an infected individual and a healthy person (like blood transfusion or needle sharing):

Suppose a mosquito bites an individual suffering from AIDS and in the process sucks up some T cells infected with HIV along with RBCs. Then it bites another person not suffering from the disease, and transfers these infected T cells. Isn't there a high probability of the second individual contracting HIV?

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    $\begingroup$ Well.. that would probably be a much more important vector of transmission than sex or blood transfer, especially in the right parts of Africa. The number of infected there is rather big, so if mosquitoes were able to routinely transmit the virus, almost everyone would be infected by now. Of course, this is just a relatively weak conjencture, but it's a decent first guess. $\endgroup$
    – Luaan
    Apr 4, 2016 at 13:41
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    $\begingroup$ @Luaan: And yet, not everyone in Africa has Malaria... $\endgroup$
    – eggyal
    Apr 6, 2016 at 6:57
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    $\begingroup$ @eggyal That's not a bad argument. I suppose it's a combination of natural resistance, improved artificial defenses and perhaps the past mass deployments of insecticides. And of course, not all of Africa has massive mosquito trouble that's why I said "especially in the right parts of Africa". More importantly, malaria isn't necessarily terminal, and the people who survive are immune to further infection - and when it is terminal, it kills quite quickly. On the other hand, AIDS is a very prolonged infection. If you're dead, you're no longer part of the statistic :) tinyurl.com/yolhob $\endgroup$
    – Luaan
    Apr 6, 2016 at 7:30

2 Answers 2


No, this is not possible. There are a few reasons for that, but most important are that the only thing a mosquito injects is its own saliva, while the blood is sucked into the stomach where it is digested.

To be able to infect other people HIV would need to be able to leave the gut intact and then also be able to replicate in the mosquitos which it cannot do, due to the missing of the CD4 antigen on the surface of the insect cells. These are needed as a surface receptor for the virus to bind and enter the cells. This is also true for other blood sucking insects like bed bugs or fleas.

Other pathogens can do this, examples would be Yellow fever or Malaria. In Yellow fever the virus first infects epithelial cells of the gut, then enters the blood system of the insect to finally end up in the salivary glands, where the virus is injected together with the saliva into the biten person. In Malaria the pathogen is also able to leave the gut region and mature in the salivary glands.

HIV can only be transmitted through blood (either through direct transmission, operations etc.), through semen (cum), pre-seminal fluid (pre-cum), rectal fluids, vaginal fluids, and breast milk. See reference 3.


  1. Why Mosquitoes cannot transmit AIDS
  2. Can we get AIDS from mosquito bites?
  3. HIV Transmission Risk: A Summary of Evidence
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    $\begingroup$ Is there a zero probability that tiny droplets of blood remain on the proboscis of the mosquito long enough for said mosquito to inject its proboscis into the bloodstream of another person? In particular, in what physical aspects is the proboscis different than a needle or razor? I am not talking about blood sucked into the gut of the mosquito, I am talking about blood remaining on the proboscis. $\endgroup$ Apr 5, 2016 at 6:08
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    $\begingroup$ @MarcusJuniusBrutus Very interesting question - I've asked it as a follow up question Why doesn't blood remain on a mosquito's proboscis in quantities that could spread blood-borne diseases? $\endgroup$ Apr 5, 2016 at 9:33
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    $\begingroup$ What if you swatted the mosquito while it was attached? Leeches, for example, will vomit previously ingested blood into you if stressed. $\endgroup$
    – OrangeDog
    Apr 6, 2016 at 13:45
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    $\begingroup$ @OrangeDog Good point, I have read something about this somewhere, I have to only find it back. $\endgroup$
    – Chris
    Apr 6, 2016 at 13:52
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    $\begingroup$ "Would it be posssible for a swatted mosquito that previously fed off a HIV carrier to infect your blood through the hole it made, or a nearby cut?" (copied from comment directed at Chris by @user2104648, posted as a now deleted answer) $\endgroup$ Apr 8, 2016 at 12:33

I am not a medical doctor but in my view this is within the realms of possibility. The probability has been estimated by Princeton at 1 in 10 million. This is per bite, assuming - I presume - that the mosquito that bit you was just feeding on an HIV-infected person of sufficiently high viral load. It is not against the laws of Physics that blood cells can remain for some time on the proboscis or other mouth-parts of a mosquito.

Whether this is probable is a matter of interpretation depending on your definition of 'probable'. But your question is about possibility, not probability. Personally, given that this is comparable, if not lower, to the probability of being struck by lightning I wouldn't give it a second thought.


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