Isolation of the patient is an effective preventive step. The patient should restrict his activities especially in the common areas used by others.
Personal items used by him, even eye drops, should not be shared with others. A tissue or clean handkerchief should be used for wiping the watery secretion from the eye. Hands should be washed frequently.
In some viral infections like small pox, our body will develop lifelong immunity once affected. That means, the same disease will not affect the same person again throughout his life.
But viral conjunctivitis is not like that. Like common cold virus, this group of Adeno-virus has many sub-groups. A different sub-group causes each epidemic.