AIDS is spread through blood transmission from infected persons. Though mosquitoes suck blood from the infected person, why is it not possible for mosquitoes to spread this disease?
HIV does not survive outside the body for very long, and it does not replicate in insects. In addition, mosquitoes transmit malaria and other infections when they inject saliva into the victim.
HIV does not get into the insect's saliva much at all, and mosquitoes do not inject blood into the victim. Furthermore, blood that remains on the bug's mouth or other body parts after it bites an AIDS victim also does not pose much risk, because the amount of blood present is very small, and the insect usually does not go directly from one feeding to another.
Many people think of mosquitoes as tiny, flying hypodermic syringes, and if hypodermic needles can successfully transmit HIV from one individual to another then mosquitoes ought to be able to do the same.
However, even if HIV-positive individuals did circulate high levels of virus, mosquitoes could not transmit the virus by the methods that are employed in used syringes.
Most people have heard that mosquitoes regurgitate saliva before they feed, but are unaware that the food canal and salivary canal are separate passageways in the mosquito. The mosquito's feeding apparatus is an extremely complicated structure that is totally unlike the crude single-bore syringe. Unlike a syringe, the mosquito delivers salivary fluid through one passage and draws blood up another. As a result, the food canal is not flushed out like a used needle, and blood flow is always unidirectional.
The mechanics involved in mosquito feeding are totally unlike the mechanisms employed by the drug user's needles. In short, mosquitoes are not flying hypodermic needles and a mosquito that disgorges saliva into your body is not flushing out the remnants of its last blood meal.
Vellore, Tamil Nadu