I thought the same.
maybe lillya(?) is unconsciously using pi-chan's power??? when she secretly don't like the girls and ishuca-san.... i guess.
Or Ishuca was suppressing pi-chans powers but now that he hasnt been in contact with pi-chan he is using lily to spread the illness... i dunno >.<
i am curious in the warning the water demon they met that is sleeping now gave to them about pii-chan though.
Lilly is very suspicous (most likely spelled that wrong). Pi-chan didn't start coughing til Isucha and Blood left and Lilly's had contact with him although she seems fine but its weird how Isucha started feeling bad when he was in contact with her.