Disease

Some powers expose a creature to a disease. If a creature is exposed to a disease one or more times during an encounter, it makes one saving throw at the end of the encounter to determine if it contracts that disease. If the saving throw fails, the creature is infected.

Published in Monster Manual, page(s) 281, Monster Manual 2, page(s) 217, Rules Compendium, page(s) 310, Monster Vault: Threats to the Nentir Vale, page(s) 122.