Mosquito uses two different tubes to suck up blood and to inject saliva
It never inject back the blood that was consumed before. Since these 2 tubes are isolated from one another. HIV in blood can not get in to Saliva and to another human.
How Mosquito transmits Malaria?
Insect-borne diseases like Malaria, Dengue are spread because they multiply within the mosquito & its salivary glands – but HIV is get killed by Mosquitoes digestive system
How HIV gets transmitted by Syringe & needle?
Syringe needle system gives air tight container which allows HIV to survive and get transmitted. on other hand Mosquitoes blood sucking tube is open to environment and HIV is gets killed immediately.
What if the Mosquito bit in fraction of seconds after biting HIV infected person or what if some one eats mosquito by mistake?
Even if it was possible for the mosquito to inject HIV into an uninfected person, the quantity of the HIV that goes inside mosquito is very less; that the person would have to be bitten by ten million such mosquitoes, in order to receive one unit of HIV. The possibility for that is almost Zero %
Conclusion
Remember that the 'H' in 'HIV' stands for human — only people can pass HIV on to other people
