After a characteristic incubation period following aerosol exposure, most BW agents present as an initial influenza syndrome with fever, chills, malaise, headache, and myalgia. Some BW agents rapidly develop into a pulmonary syndrome with dyspnea, cyanosis, chest pain, and radiological abnormalities. Liver involvement is indicated by rising liver enzymes, with or without jaundice. Encephalitis may occur with some select viral agents, typified by photophobia, confusion, nuchal rigidity. Maculopapular, vesicular pustular, or ulcerative skin lesions with or without bleeding abnormalities may occur with some agents. Unexplained death or flaccid paralysis may be indicative of the use of biological toxins.