1. Potential Biowarfare Agents and their
Methods of Spread
Dr Kamran Afzal
Classified Pathologist and Microbiologist

2. I. Potential BW Agents

3. Potential BW Agents: CDC Category A
FEATURES AGENTS
 Easily disseminated or  Anthrax
transmitted person -  Plague
person  Smallpox
 High mortality – major
 Tularemia
public health impact  Viral
 Public panic and social
haemorrhagic
fevers
disruption  Botulinum toxin
 Special action for public
health preparedness

4. Potential BW Agents: CDC Category B
FEATURES AGENTS
 Moderately easy to  Brucellosis
disseminate
Q fever
 Moderate morbidity, low
mortality  Glanders & melioidosis
 Require enhancement of  VEE, EEE and WEE
diagnostic capacity and  Enteric pathogens
surveillance
 Other toxins

5. Potential BW Agents: CDC Category C
FEATURES AGENTS
 Emerging agents  Nipah virus
 Availability
 Hantaviruses
 Easy to produce and
 Tickborne HF
disseminate
 Potential for high mortality  Tickborne encephalitis
and morbidity  Yellow fever
 MDR-TB

6. Desirable Features of Biological Agents to
be used as Biological Weapons
Less expensive
Available
Easily transported/concealed and dispersed
Incubation period “Hides Tracks” of perpetrator
Modifiable (resistance, virulence)
Produce ‘anxiety factor’, over-loading health services
Produce social disruption, reduce productivity
Impact on morale, create epidemic

7. Characteristics of BW Agent
Infective dose should be low
Should be highly contagious
Should be stable and robust
Can be aerosolized (1-10 µm)
Survives sunlight, drying, heat
Cause lethal or disabling disease
Person-to-person transmission
Should consistently produce given effect, death or disease
Should have a short and predictable incubation period

8. Characteristics of BW Agent
The agent should be amenable to easy and economical mass
production
Storage methods should be available
Target population should have little or no natural or acquired immunity
Prophylaxis against the agent should not be available to the target
population
Little or no treatment for the disease caused by the agent should be
available
The aggressor should have means to protect its own forces and
population

9. Characteristics of BW Agent
It should be capable of efficient dissemination
Stable during dissemination. If it is to be delivered via an aerosol, it
must survive and remain stable in air until it reaches the target
population
If it cannot be delivered via an aerosol, living vectors (e.g. fleas,
mosquitoes or ticks) should be available for dispersal of some form of
infected substrate
After delivery, the agent should have a low persistence, surviving only
for a short time, thereby allowing a prompt occupation of the attacked
area by the aggressor’s troops

10. Aerosol : Infectivity Relationship
Particle Size Infection
The ideal aerosol (Micron, Mass Severity
Median
contains a homogeneous Diameter) Less
population Severe
of 2 or 3 micron 18-20
particulates that contain
one or more 15-18
viable organisms 7-12
Maximum human 4-6
(bronchioles)
respiratory infection is a
particle that falls within 1-5 (alveoli)
1 to 5 micron size More
Severe
Source: San Diego Medical Society

11. Uniqueness of Biological Attacks
Responders – medical
Response System – untested
Medical System may be a target
Biological
 Onset - incubation, primary cases
 Secondary cases – contagiousness, contamination

12. Difficulties in use
Incubation period ranges from hours to days
Rain, sunlight and temp extremes reduce the virulence
Natural and acquired immunity against pathogens make it impossible
to predict the exact number of casualties from any BW attack
Consequently, BW today is primarily for harassment and special
operations

13. Potential BW Agents
Bacteria Mode of I.P. Mortality Vaccine Treatment
Transmission
Bacillus anthracis A, D, I 1–7 5-100 + E
(Anthrax)
Brucella group A, D, I 5-21 2-6 + E
(Brucellosis)
Francisella tularensis A, D, I, V 1-10 <30 ++ E
(Tularemia)
Yersinia pestis A, V 2-6 25-100 +++ E
(Plague)
Vibrio cholerae (Cholera) I 1-5 15-90 +++ E
Corynebacterium diphtheriae A, D 2-5 5-12 +++ E
(Diphtheria)
A - Aerosol D - Direct contact I - Ingestion V - Vector E - Effective
treatment available N - Non-specific treatment

14. Potential BW Agents
Salmonella typhi I 6-21 7-14 +++ E
(Typhoid fever)
Rickettsiae V 6-15 10-40 +++ E
Rickettsia prowazeki
(Epidemic or louse-borne typhyus)
Rickettsia mooseri V 6-14 2-5 E
(Endemic or flea-borne typhyus) -
Rickettsia rickettsii V 3-10 30 (Approx) E
(Rocky Mountain spotted fever) -
Coxiella burneti A, I 14-21 <1 ++ E
(Q fever)
A - Aerosol D - Direct contact I - Ingestion V - Vector E - Effective
treatment available N - Non-specific treatment

15. Potential BW Agents
Viruses Mode of I.P. Mortality Vaccine Treatment
Transmission
Group A Arboviruses V 4-24 60 - N
Eastern equine encephalitis (EEE) (Approx)
Venezuelan equine encephalitis V 4-24 <1 ++ N
(VEE)
Group B Arboviruses V (mosquito) 4-24 - - N
St. Louis encephalitis
Japanese B encephalitis V (mosquito) 5-15 10-80 ++ N
Russian spring-summer V (tick) 7-14 3-40 + N
encephalitis (RSSE)
Yellow fever V (mosquito) 3-6 5-40 +++ N
A - Aerosol D - Direct contact I - Ingestion V - Vector E - Effective
treatment available N - Non-specific treatment

16. Potential BW Agents
Dengue virus V (mosquito) 4-10 <1 - N
Ungrouped Arbovirus V (mosquito) 4-6 1 - N
Rift Valley fever virus
Poxvirus A, D 7-16 1-35 +++ N
Variola virus (Smallpox)
Myxovirus A, D 6-365 100 ++ E
Rabies virus
Influenza virus A, D 1-2 - +
H5N1 E
A - Aerosol D - Direct contact I - Ingestion V - Vector E - Effective
treatment available N - Non-specific treatment

17. Potential BW Agents
Fungi A, D 10-21 1-51 - E
Coccidioides immitis
(Coccidioidomycosis)
Histoplasma A 5-18 - - E
capsulatum
A - Aerosol D - Direct contact I - Ingestion V - Vector
E - Effective treatment available N - Non-specific treatment

18. Potential BW Toxins
NAME SOURCE EFFECTS
Botulinum toxin A Clostridium botulinum Dizziness, sore throat, and dry mouth
followed by paralysis
Death by suffocation (respiratory
paralysis) or heart failure
Ricin Castor bean plant Nausea, vomiting, bloody diarrhea, and
drowsiness
Death by kidney failure (uremia)
Saxitoxin Dino-flagellates Tingling around face, loss of sensation
(Shellfish toxin) in extremities
Death by paralysis
Tricothecenes- Fungus Nausea, vomiting, diarrhea
myco toxins Death by internal hemorrhaging

19. Comparison of Bioterrorism
Toxins and Chemical Agents
Toxins Chemical
Natural origin Man-made
Generally more toxic Generally less toxic
Difficult, small-scale Large-scale, industrial
production production
None volatile Many volatile
Aerosol delivery Vapor or aerosol delivery

20. Comparison of Bioterrorism
Toxins and Chemical Agents
Toxins Chemical
Odorless and tasteless Noticeable odor or taste
Not dermally active* Dermally active
Legitimate medical uses No legitimate medical use
Many effective immunogens Poor immunogens
* Exceptions, trichothecene (T-2) mycotoxins

21. II. Methods of Spread

22. Modes of Exposure / Routes Of Entry
Inhalation
 Inhalation of spores, droplets and aerosols
 Powder
 Spray - Small scale
- Large scale
 Explosive
 Pulmonary infection is by far most effective

23. Ingestion
Food
 Potentially significant route of delivery
 Secondary to either purposeful or accidental exposure to aerosol
Water
 Capacity to affect large numbers of people
 Dilution factor
 Water treatment may be effective in removal of agents

24. Inoculation / Contact / Absorption
 Cuts/Abrasions on skin or mucosal membranes
 Vectors (mosquitoes, ticks, fleas and lice)
 Fomites
 Explosive

25. Delivery via Aerosols (Inhalation)
Aerosol- Small droplet particles composed of many organisms
dispersed into air and carried by air currents
Explosive bomb-lets consist of low grade explosive, explode on
impact and release biological agent which disseminates as aerosol
Generators have biological agents filled in a pressure chamber
and are released through a nozzle
Agent may by released during flight over enemy area or covertly
set up in the target area
Slurred mixture – Spray of Anthrax and Botulinum toxin

26. Spray tanks can be carried by aircrafts or missile. Tanks contain large
quantity of agent and can be effective over a large area
Variables altering effectiveness of a delivery system
Particle size of the agent
Stability of the agent under desiccating conditions, UV light
Wind speed, wind direction, and atmospheric stability

27. Anthrax Transmission
Inhalation
Spores in Postal envelopes
Spray
 Aeroplane
 Spray machine
Aerosol
 Aerialbombs
Skin inoculation
Ingestion

28. Smallpox Transmission
Common: Person – to –person by large airborne droplets
 Face-to-face contact (i.e., 6 feet)
 Should be interrupted by mask protection (e.g., NIOSH N-95)
Rare: Airborne over long distance
Rare: As fomites (e.g., Bed linens)
Not transmitted by food

29. VHF Agents Transmission
From reservoirs to vectors to humans
Less common route
Contact with infected animal tissues,
urine, feces, and other excreta
Via Aerosols

30. Conclusion
BW agents are easy to acquire, synthesize and use (Poor man’s
nukes)
Small amount of agents can kill hundreds of thousands of
people in a metropolitan area
Concealment, transportation, and dissemination of biological
agents relatively easy
BW agents are difficult to detect or protect against; being invisible,
odorless, and tasteless, dispersal can be performed silently
Transmitted via inhalation, ingestion and inoculation