I generally don't isolate for this unless the bird is really acting unwell, and maybe being picked on by other birds or being kept from food and water. If he has trouble seeing because of his eye, then that might be a reason to separate him if he's having trouble, until the eye clears up. If he has a lesion/scab/spot very close to the eye, that can cause a secondary bacterial infection in the eye, thus the drops. Since the mosquitos are everywhere, it's likely others are already exposed anyway. They do build resistance after being infected and recovering, so generally a one time thing for each bird. In some cases it can be so mild as to be almost not noticable, in other cases more obvious with lots of lesions. Keeping feeders, waterers, and runs clean can help minimize transmission through the scabs being sloughed off. If you live in a place where it's a big problem, or see very many cases of wet pox, then there is a vaccine available, but needs to be given to healthy birds generally between 8-12 weeks old (at least 8 weeks old, and 4 weeks before point of lay).