Table 1. Summary of clinical signs of H9N2 viruses from the Y439 and Y280 lineage in farms and animal experiments, respectively.
| Cases | Species | Y439 lineage | Y280 lineage | ||
|---|---|---|---|---|---|
| Clinical signs | Reference | Clinical signs | Reference | ||
| Field (farm) | Chicken (commercial) | Egg drop, respiratory sign, depression, diarrhea, weight loss, decreased feed intake, mortality (0%–30%) | [2,5,61,63] | Egg drop, respiratory signs (coughing, sneezing, gasping), mortality (10%–40%) | [1,2,62] |
| Animal experiment | Chicken (SPF) | No mortality, depression | [5,63,65,66] | No mortality, depression, diarrhea, decreased feed intake | [16,17,19,64,66,71,89,97,102] |
| Viral shedding: higher titer via CL route | Viral shedding: higher titer via OP route | ||||
| Mice | Mostly no clinical signs and mortality, weight loss, inappetence | [5,92,107] | Inappetence, huddling, ruffled fur, labored breathing, hunched posture, respiratory distress, weight loss, mortality (0%–30%) | [2,36,52,82,83,89,91,92,93] | |
Bold: observed major clinical symptoms.
SPF, specific-pathogen-free; OP, oropharyngeal; CL, cloacal.