Every year a viral photo of a bed bug on a tube seat kicks off a wave of worry. In practice, catching bed bugs from a short Underground journey is very uncommon — bed bugs prefer to feed at night in a stationary host, not on a moving commute.
The real Underground risk is transfer: an infested coat, bag or piece of luggage brushing against yours. If you've been on the tube with a suitcase from a hotel, the suitcase is what to worry about — not the seat.
When you get home, don't put bags or coats straight onto the bed. Tumble-dry soft items on high heat for 30 minutes, and give luggage seams a torch inspection before storing it.