Hemorrhagic septicemia is a highly fatal bacterial disease seen mainly in cattle and water buffalo. In susceptible animals, the clinical signs often progress rapidly from dullness and fever to death within hours. Because the disease develops so quickly, few animals can be treated in time, and recovery is rare. Subclinical carriers can introduce hemorrhagic septicemia into a herd. Young animals are mainly affected in endemic regions, and outbreaks are particularly common during rainy weather, when the organism can spread readily. In areas where cattle have no immunity, severe disease is expected to occur in all ages.