White spot syndrome virus has
The principle of microbial physiology explains that growth regulation and host interactions follow molecular programs. Hence both vertical and horizontal transmission fits best because it corresponds to prokaryotic strategies, as documented in authoritative sources on microbiology.
Ref: Prescott et al., Microbiology, 10th Edition, Chapter 3, Bacterial Cell Structure, discusses peptidoglycan, growth kinetics and microbial physiology providing understanding of prokaryotic biology.