The opinions about the meaning of the text on the last page of the Voynich Manuscript (fol.116v) are diverse. The first word of the first line 'pox' has suffered various interpretations - from devil to goat.
The first recorded outbreak of the Great Pox (syphilis) was in 1495 when the army of the French King Charles VIII was marching on their way home spreading the disease on its way. The illness became known as 'the French disease' and the French called it 'Neapolitan disease'. Charles VIII entered Naples in February 1495. Few months later the mass outbreak of the symptoms of the new illness in his army made him pack and head back home instead of attempting other conquests. The symptoms among the foot-soldiers were visible at the battle of Fornovo - five months after the conquering of Naples.
Syphilis (the great pox) was brought to Europe supposedly couple of years earlier by Columbus and his crew among 'the gifts' of the New World. The captain of Pinta, Martin Pinzon, died of the new disease in 1493. As new illness it brought much more damage at first, than it does today.
Albrecht Durer depicted person suffering from the Great Pox in 1496.
So if we continue to speculate about the possibility of the Voynich Manuscript to be the book captured from the tent of the King of France at the Battle of Fornovo, then a quick remark about pox on the last page in the last minute makes some sense.
Among the first treatments tried for the 'pox' was fumigation. The patient was locked in a box with mercury that has been heated to evaporate. Maybe the last line of the 'recipe' on fol. 116v refers to this process with the word 'mm gas' (mercurium gas :) ) and the word 'vbren' may be short for the German verbrennen - burn.
Anyway, all this is wild speculation, in which I engage only because it is no more outrageous than most of the mainstream suggestions about the text.