Primeval Episode 3.05 Episode 18

The team are faced with a highly unusual and dangerous threat from the future: a deadly flesh-eating fungus.

When a transient anomaly opens, an unfortunate assistant accidentally wanders through to a hot damp world. He breaths in some spores which he then transfers to our world.

These spores belong to an incredibly aggressive, fast-growing fungus that first invades and kills its human hosts before reanimating their bodies to seek out new hosts.

When all solutions (including fire and water) fail to destroy the creature the team must deal with the possibility that the fungus will spread through the whole country, absorbing everyone it encounters and becoming bigger and more dangerous all the time.