give my an union.

nah. pretty much any light mech with a flamer. flamers kill, cauterize, set buildings on fire, and make terrain impassable once alight. 100 m is also freaking large range.
Harrasser D and firestarters present themselves. even hollanders could do it. it just has to pack JJ or be mobile enough for urban... renewal.
my method? scorched earth. leave nothing alive, purify the world in fire. any other weapon leave remains. remains which can rot, rise again, or allow the disease to survive.
1. land and surround infected zone.
2. burn any obstruction down around the zone. no vegetation or rubble left standing. set up a killzone.
3. all unidentified entities trying to enter or leave the zone are instantly burned to ash. this includes animals esp. birds.
4. a pair of flamer equipped mechs enter the zone while the rest stay back. they begin to systemically burn down everything in the zone.
5. stay alert for several days after the last fires died out. keep a lookout for signs of other infection herds.
6.

7. profit.