What is considered the most virulent Brucella species for humans?

B. melitensis is considered the most virulent Brucella species for humans due to its high pathogenicity and association with severe disease. It is primarily transmitted through unpasteurized dairy products and can lead to a range of symptoms, including undulant fever, sweats, malaise, and joint pain. The virulence of B. melitensis is often linked to its ability to evade the host's immune response and establish persistent infections, which can cause long-term complications.

The other species, while they can infect humans, generally do not pose the same level of risk. B. abortus is primarily associated with cattle and is less virulent for humans, typically causing milder infections. B. suis has a higher virulence than B. abortus but is still not as virulent as B. melitensis. B. canis is the least pathogenic to humans compared to the others and often results in less severe disease outcomes. Therefore, the identification of B. melitensis as the most virulent species is crucial for understanding the risks associated with brucellosis and for implementing appropriate preventive measures in at-risk populations.