[imakesnowflakes]

>is whether it can infect A's friends D through Z, all of whom don't have malaria, presumably because they weren't bitten by an infected mosquito in the last couple weeks...

The point is, with mosquitos, a larger percentage of population (A's friends) will already be bitten by infected mosquitos, making it harder for the airborne strain to find a fresh host...

Thanks for the info regarding Malaria..