I seem to remember there being one in the earlier editions, but cannot seem to find it in 4th ed. Except as a universal heal spell at rank six

Any ideas?

It is in the Earth Spells, Jourin's Balm at Mastery Level 1 if I remember correctly.

There are no easy and good disease removers until high ranks. Jurojin Balm's is your best bet, but it only allows you to take another try at naturally overcoming the disease, so against truly deadly illness or poison, it will do no good. Which is fine, IMHO, because it doesn't allow a Rank 1 Shugenja to instant-solve sickness and poison related plots.