Not sure what you mean by “lose the DNA identity of their hosts”.
A sperm or egg cell is produced by meiosis. The original cell has the DNA of the person, one of each chromosome from mom and one of each from dad. This is mixed up so the NEW resulting DNA pattern in the reproductive cell is unique to that cell, and that cell will only have HALF the DNA of the parent cell.
When the sperm and the egg combine each half forms a new whole - but nothing happens with the DNA other than that it is combined with the ‘missing’ half.
The sperm cell is alive, the egg is alive - both have the DNA of the parent - but in a new configuration.
What I mean is....the new organism does not possess the same dna as the sperm - nor does it possess the same dna as the egg.
Rather - it possesses the new arrangement - the DNA that will follow that new life for the rest of its life.
Yes - the new DNA code is comprised from the mother and father - but is not the same. It is unique to this particular life.
It is the point in time we can point to and say “there”! - That person’s origin is here!
That is when human development begins. We all learned this in science class.
Yes....this life will continue to grow a few days later as it implants into the uterine lining.
If implantation does not go well, it will die.
That does not mean it was not alive prior to implantation.