Science Questions

Can mosquitoes pass on HIV?

If a mosquito bites someone with HIV and then goes and bites someone else will it pass on the disease? Alison, Norfolk

Chris - Thankfully, no.  Because otherwise Africa would have a much worse problem than it currently has where there are something like 4 million new cases of HIV every year.  They’re thankfully not caused by mosquitoes.  If they were we would all be in really serious trouble because it would be like malaria.  The reason is really simple because we know that mosquitoes are very good at transmitting viruses, certainly things like dengue gets spread by mosquitoes and that’s a virus.

There’s a very good reason why this isn’t the case with HIV which is that HIV is a very specialist virus which has on its surface viral velcro, molecular docking stations that lock on to certain parts of cells, CD4+ cells which you only find in us, in humans.  There’s related versions of HIV in chimpanzees (SIV) and they have their own specific cells that it locks onto.  Because those specialist cells are only found in us HIV is a very fragile virus.  It can’t survive in the mosquito’s intestine, it can’t latch onto cells in the mosquito, therefore the mosquito doesn’t get infected.  Therefore the mosquito can’t amplify the dose from the person it bites.  Therefore it can’t infect the next person because it can’t inject more viruses than it took in.  HIV is very poor at infectivity.  It’s actually very hard to catch, believe it or not.  You can reassure everyone you’re not going to catch HIV from a bite.

April 2009