Module 2 of 10 ~35 minutes

Biological Agents of Concern

Category A, B, and C Threat Agents - Recognition and Clinical Features

6 Category A Agents
Educational Videos
Clinical Tables

Learning Objectives

1

Classify biological agents into CDC Categories A, B, and C based on threat level

2

Identify clinical presentations of Category A biological agents

3

Describe transmission routes and infection control requirements for each agent

4

Explain treatment protocols and nursing interventions for biological agent exposure

5

Differentiate between agents based on pathognomonic clinical features

CDC Classification System

The CDC classifies potential biological threat agents into three categories based on their danger, ease of dissemination, and public health impact.

A

Highest Priority

Mass casualties

  • Anthrax
  • Smallpox
  • Plague
  • Botulism
  • Tularemia
  • Viral Hemorrhagic Fevers
B

Second Priority

Moderate morbidity

  • Brucellosis
  • Q Fever
  • Ricin toxin
  • Typhus fever
  • Viral encephalitis
  • Food/water threats
C

Emerging Threats

Future potential

  • Nipah virus
  • Hantavirus
  • SARS/novel coronaviruses
  • Emerging infectious diseases
  • Engineered pathogens

Anthrax (Bacillus anthracis)

Type

Gram-positive, spore-forming bacterium

Spore Survival

Decades in soil

Person-to-Person

NOT transmitted

PPE Required

Standard Precautions

Video: Understanding Anthrax

Clinical Forms of Anthrax

Form Route Presentation Mortality
Inhalational Inhaled spores Flu-like symptoms → severe respiratory distress, widened mediastinum Up to 95%
Cutaneous Skin contact Painless papule → vesicle → BLACK ESCHAR <1% with treatment
Gastrointestinal Ingestion Nausea, vomiting, bloody diarrhea, ascites 25-60%

CLINICAL PEARL - Pathognomonic Finding

Widened mediastinum on chest X-ray is the hallmark finding of inhalational anthrax. This finding in a previously healthy patient with flu-like symptoms should immediately raise suspicion.

Treatment

Antibiotics (60 days)

  • • Ciprofloxacin (first-line)
  • • Doxycycline (alternative)

Antitoxins (severe cases)

  • • Raxibacumab
  • • Obiltoxaximab

Smallpox (Variola major)

HIGHLY CONTAGIOUS - AIRBORNE + CONTACT PRECAUTIONS

Mortality: 30% in unvaccinated populations | Eradicated 1980, lab stocks remain

Smallpox vs. Chickenpox - Critical Differentiation

Feature Smallpox Chickenpox
Distribution CENTRIFUGAL (face, extremities) Centripetal (trunk)
Lesion Stage All lesions SAME stage Multiple stages simultaneously
Palm/Sole Involvement Commonly involved Rarely involved
Fever Timing BEFORE rash (prodrome) With rash onset
Lesion Depth Deep, firm lesions Superficial
Patient Condition Very ill (toxic) Usually mild illness

Required Precautions

  • Negative pressure room
  • N95 respirator (minimum)
  • Gown and gloves
  • Eye protection
  • Limit patient movement
  • Restrict visitors

Plague (Yersinia pestis)

Type

Gram-negative bacterium

Natural Vector

Fleas (rodent reservoir)

Bioterrorism Form

Aerosolized → Pneumonic

Person-to-Person

YES (pneumonic only)

Bubonic

Painful lymph nodes (buboes), fever, headache

NOT person-to-person

Septicemic

Septic shock, DIC, gangrene of extremities

NOT person-to-person

Pneumonic

Severe pneumonia, hemoptysis, rapid progression

HIGHLY CONTAGIOUS

INFECTION CONTROL ALERT

  • • Pneumonic plague requires DROPLET PRECAUTIONS (surgical mask within 6 feet)
  • • Treatment must begin within 24 hours of symptoms
  • • Streptomycin or Gentamicin preferred; Doxycycline alternative
  • • Post-exposure prophylaxis required for close contacts

Botulism (Clostridium botulinum toxin)

Type

Neurotoxin (most potent known)

Mechanism

Blocks acetylcholine release

Result

Flaccid paralysis

Person-to-Person

NOT transmitted

Classic Presentation

Descending, symmetric flaccid paralysis with cranial nerve involvement. Patient is ALERT with clear sensorium (unlike stroke).

Diplopia Dysarthria Dysphagia Respiratory weakness NO FEVER

CLINICAL PEARL - Key Differentiator

Alert patient with descending paralysis = Think botulism

Antidote: Botulinum antitoxin (obtained from CDC). Mechanical ventilation often required.

Tularemia (Francisella tularensis)

One of the most infectious bacteria known—as few as 10 organisms can cause disease via inhalation.

Form Presentation Notes
Pneumonic Fever, cough, chest pain, respiratory distress Bioterrorism route
Ulceroglandular Painful ulcer at inoculation site + lymphadenopathy Most common natural form
Typhoidal High fever, no localizing signs Systemic infection

Treatment

Streptomycin or Gentamicin (preferred); Doxycycline or Ciprofloxacin (alternatives)

Standard Precautions adequate—not transmitted person-to-person

Quick Reference Chart

Agent Key Finding Person-to-Person PPE
AnthraxWidened mediastinumNOStandard
SmallpoxCentrifugal rash, same stageYESAirborne + Contact
Plague (pneumonic)Hemoptysis, rapid pneumoniaYESDroplet
BotulismDescending paralysis, alert patientNOStandard
TularemiaUlcer + lymphadenopathyNOStandard
VHFsBleeding, shockYES (contact)Enhanced barrier

Key Takeaways

Category A agents pose highest risk due to ease of dissemination and high mortality

Smallpox and pneumonic plague require enhanced isolation precautions

Anthrax, botulism, and tularemia are NOT transmitted person-to-person

Recognize pathognomonic findings: widened mediastinum (anthrax), centrifugal rash (smallpox)

Module 1: Introduction Module 3: Clinical Recognition