No AIDS via Mosquitoes

I ran into yet another question which made me wonder why it (the question, not the answer) hadn’t even occurred to me. As icing on the cake, the answer turned out to be even more fascinating.

 

The question? If sharing a needle can spread AIDS, why can’t a mosquito spread it too? They look like “tiny flying syringes”, they pierce the skin, they draw blood, they bite multiple people. Those details are relevant to malaria, why not AIDS?

 

Now for the answer. A syringe is a single tube. Blood goes in, blood comes out. A mosquito’s proboscis, on the other hand, has two tubes. One sucks blood out. The other injects saliva into you (to prevent the blood from clotting).

“You’re not getting the last person’s blood. You’re getting mosquito spit.”

HIV, the virus that causes AIDS, does not live in spit. Thankfully.

 

In addition, a syringe or a razor blade doesn’t digest anything. It is a neutral surface on which the HIV virus can stay peacefully. A mosquito’s stomach, on the other hand, is a “digestive furnace”. Enzymes break down whatever enters. The HIV virus cannot survive in such a hostile environment.

 

Wait, you say, how do the microbes that cause malaria survive in the same digestive furnace? Well, those microbes have evolved over eons to be able to survive in the mosquito’s gut, reach the next stage of their reproductive cycle, and then move to the salivary glands of the mosquito to be inserted into the human. HIV hasn’t evolved for this kind of lifecycle.

“It’s a human virus. Inside an insect, it’s lost (and dead).”

 

Lastly, there is maths. A needle holds several drops of blood, each with millions of copies of the virus. A mosquito’s mouth parts would have a very tiny amount of viral copies as residue (remember, the ingested blood went to its stomach). That tiny quantity left in the mosquito’s mouth isn’t anywhere near enough to cause any problems to humans, even if they get injected when it bites.

 

A fascinating question and answer session.

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