What characteristics does a organism described as highly virulent have?

A highly virulent organism possesses characteristics that enhance its ability to cause disease and evade host defenses. These may include the production of potent toxins, mechanisms to evade the immune response, and the ability to rapidly replicate and spread within the host. Additionally, such organisms often exhibit a high capacity for adherence to host tissues and may have evolved specific adaptations that facilitate transmission between hosts. Overall, high virulence is associated with increased pathogenicity and a greater likelihood of causing severe disease.