If they have what to feed on, yes, they might spread to other lenses that use the same body. Some of the fungus feed on the deteriorated balsam that holds groups of lenses together, others feed on the deteriorated oil where there is a shutter unit between the lenses.
Originally Posted by Katie
Thats why its good to run most central shutters almost dry, with tiny scent of oil or graphite on critical pivots.
The best prophylactic is to have Your lenses cleaned with alkaline solution every now and then. UV is not an option when acid environment is present inside the lenses.. as in most cases.
Generally speaking, fungus or other types of bacterias are very intelligent, so once they are present.. You will need a lot of luck and mojo to save that lens.
Cellulose triacetate films can develop bacterias relatively fast, when not stored properly. Thats another way to get Your camera infected.