Possible Clues:

• Gone to the bad for a month, I see
• In the autumn, one cold could be infectious
• Of wound, infected and with pus
• Of wound, filled with pus
• Putrefying
• See after the first of the month how this has gone to the bad
• Thus odd pet is held to be infected
• 'A short month, I see. That's bad (6)'
• 'Gone to the bad for a month, I see (6)'
• 'The pets have gone to the bad, I see (6)'