Enroute Controller experienced a loss of separation event indicating more vigilance should have been exercised during the relief briefing.

Narrative

Received position relief briefing for Sector 17/85 combined; immediately followed by combining Sector 16/86. Following the briefing for Sector 16/86 combination; I observed that the B717 had been issued a clearance to descend through the E145 by the previous Controller. Upon observation I immediately issued a turn to the E145 and called traffic; and as the B717 had previously had communication status transferred; I called the next sector to have them issue a turn and stop the descent. The turn and alternate instructions were too late and separation was lost. Additional factors that may be related to the event are that shortly after arriving at work today I began to feel ill. After informing my Supervisor that I was not well; I was informed that sick leave could not be granted due to the on going drug testing operations in the facility prevented anyone from leaving. As such I continued to work under the weather. Personally; I need to be more vigilant before; during; and after position relief briefings. I was blindly led to believe that all traffic was separated and I was not skeptical enough.