In a preliminary test, 120 YHV-free shrimp were injected intramuscularly with a virulent YHV stock to yield 5 × 105 (pre-patent disease level) and 2500 (carrier level) viral copies/g shrimp tissue (60 shrimp each dose). These are possible infection levels for grossly normal shrimp from normal harvest ponds (i.e., not shrimp from disease outbreak ponds)