Biological and chemical weapons are a variety of living organisms raging from bacteria's to viruses.  There are several major ones which I describe in a Table on the next page.  All these extraordinary organisms, toxins, and biological agents have extremely different qualities.  But most of them share one main attribute, they can be put in aerosols to be used as a weapon.  These organisms can remain suspended in the aerosols for hours and if inhaled will enter the bronchioles and terminal alveolus of the victim.  The aerosols can be delivered in small spray cans, airplanes, or missiles.  Anther possible routes include contamination of water and food, but the respiratory route is considered more important.
    Biological and chemical weapons can be lethal and/or disabling.  Some examples of lethal agents include anthrax, botulinum toxin, and Francisella tularensis.  Some examples of disabling agents are Staphylococcal enterotoxin B, and Coxiella burnetii. Other agents, like Yersinia pestis, produce pulmonary syndromes of the disease they produce in nature.  Person to person spread of certain agents could be crucial because the agents organism would travel on flies or mosquitoes.
    The potential impact of biological and chemical weapons could produce mass destruction.  It was estimated that if fifty kilograms of aerosolized anthrax was dropped on a population center of five hundred thousand unprotected people, in ideal weather conditions, it could kill and/or disable up to one hundred twenty-five thousand people.  With this in mind, certain chemical and biological weapons could produce mass destruction.  In addition, these agents would put a damper on our medical systems.  Enormous amounts of people would flood hospitals, who would not have the proper medications or vaccines, or the proper protective wear to deal with the organism, let alone the personnel to deal with all the injuries.
    The medical response to the use of or threat of chemical and biological weapons usage is different depending on whether contamination has already occurred.  If medical attention is provided before contamination, the proper immunization with antibiotics ay prevent illness.  Immunization is probably the most effective against chemical and biological agents.  After contamination, immunization and treatment with antibiotics and antiviral drugs may calm the symptoms.  After onset of illness, diagnosis and specific treatment for the disease are the only option.  There are several vaccines and antitoxins that exsist for a majority of the chemical and biological warfare agents.
 

References: NBC