Feeding while high fever

Tbh I wouldn't. I've pumped and dumped back when i was ill and breastfeeding. I researched a number of articles written by doctors (traumatic first breastfeeding journey which led to alot of time spent on Google) and it appears that that the antibodies in the milk only help gut health, not the whole immune system. Passive immunity is conferred at birth, I.e. most antibodies that mama has that passed to baby was in the womb, not through breast milk. Any slip or careless handling of the milk could result in the milk becoming contaminated (e.g. touching your face, then touching the pump parts and flanges) and then the germs get into the milk and passed on to baby. 40deg is a really really high fever, and while it may not necessarily correlate with the severity of the illness, you probably should concentrate of getting back to full health first. Baby will do fine with either a frozen bm stash or formula in the meantime.