Genomic analysis suggests that the outbreak probably began in December or January, but a shortage of data is hampering efforts to pin down the source.

中文翻译：

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RNA显示禽流感病毒已在​​美国奶牛中传播数月

基因组分析表明，疫情可能始于 12 月或 1 月，但数据短缺阻碍了查明来源的努力。