Bairstow's unbeaten 108 off 48 balls, with eight fours and nine sixes, see Punjab secure the win with eight balls to spare
"Shepherd will remain in Guyana where he is undergoing a period of isolation that unfortunately will extend beyond the team's travel period," the CWI said in a statement.
West Indies are sending a depleted contingent after 10 players, including test captain Jason Holder and limited-overs skipper Kieron Pollard, pulled out of the tour over COVID-19 concerns.
The CWI said all other members of the touring party have returned negative results in their final pre-travel COVID-19 tests and would reach Bangladesh in two batches by Sunday.
Beginning on Jan. 20, West Indies are scheduled to play three one-day internationals and two tests.