I don't know what kind of bird you are hand feeding but, keeping the syringes and food containers CLEAN is mandatory. I highly recommend that you buy some F10 and after rinsing in hot water soak the syringes in a 250/1 solution of F10 and take out only when you are ready to feed. You must wash the food container very well in hot water (and rinse very well) and do not save leftover feed between feedings.
I've done years of hand feeding my two chronically ill birds and believe me I learned the hard way to keep everything immaculately clean.