A family cluster of <i>Brucella abortus</i> infections possibly due to contact with a sika deer in Northeast China

Brucellosis is one of the most common zoonotic diseases worldwide. Although deer are reportedly infected by <i>Brucella</i> spp., deer-associated brucellosis cases have been rare. In this study, two patients in Heilongjiang Province, Northeast China, were diagnosed with brucellosis. They have contacted a sick sika deer before onset which was bought from another province, but have no contact with other infection sources. Molecular genotyping indicated that both were infected with <i>Brucella abortus</i>. This might be the first human cases caused by deer-associated <i>B. abortus</i> strains despite the frequent reports of <i>B. abortus</i> in deer. The role of deer in the transmission of <i>B. abortus</i> should be taken into consideration.