Animal health officials say there have been no reports of humans _________ the disease.

此题考查的是英语词汇的使用。根据题干，"Animal health officials say there have been no reports of humans _________ the disease." 可以看出，这里需要一个动词来描述人类感染疾病的情况。"contracting" 是一个合适的动词，意为“感染，染上”，符合题意。