Most of the time, we think that conjunctivitis is caused when bacteria on our hands is transmitted to the eyes when we rub our eyes before washing our hands.
There are actually other ways of transmission, including airborne droplets.
If you or someone near you sneezes, uh oh!
However, the saving grace is that airborne droplets from sneezing and / or coughing are big, so they land faster than they remain airborne.
Which means, lots of surfaces we touch in public, may be germ-laden. Eg. tap handles in public restrooms, doorknobs, lift buttons, etc. Just be aware that you have to wash your hands and wash them well before touching your eyes.
All said, none of us would get conjunctivitis too many times in our lives. That's because once our body senses a 'germ invasion', our auto-immune system immediately kicks in to eradicate the germs. Besides, not all germs will be able to adapt to the conjunctiva membrane and thrive there. Saving grace!