Sefer HaMitzvos

Negative Mitzvah 168

The High Priest is forbidden to come into contact with any dead body

Leviticus 21:11 "Nor defile himself for his father or for his mother"

The Torah cautions the High Priest to be very careful about coming into contact with a dead body.

Any type of contact is forbidden, whether it be touching or carrying (even without touching) the dead body.

Negative Mitzvah 167 cautions the High Priest not to be under the same roof as a dead body. This Negative Mitzvah cautions the High Priest not to become impure because of other types of contact with dead bodies.