Q: Will his fever affect his sperms and the sperm count?
A: Sperms are produced in the testes which are inside the scrotum. The scrotum is outside the body and is designed to keep testicles cooler than the body temperature. A temperature at or above the body temperature (about 98.6 degrees F.) may negatively affect the sperms and sperm production. That means he may produce less sperms and it can take 10-11 weeks for new sperms to be made.
A low sperm count can affect your chances to get pregnant and decrease the probability. But if you do get pregnant it's unlikely that his past fever has a negative effect on the baby.