Chapter 1. Anthrax

This chapter describes the assumptions for the anthrax scenario, including:

• the severity categories.
• the arrival pattern of casualties at the hospital(s).
• the length of stay by hospital unit (i.e., ED, ICU, and the floor).
• the path probability within the hospital(s) and the length of stay.
• the overall outcome probabilities (i.e., probability of discharge and probability of death).
• the assumed level of resource consumption per patient per day per hospital unit.

Footnotes in the text of a particular section refer to references at the end of the section. In the absence of specific references, parameter estimates were obtained from general references listed in the Hospital Module section.

1.1. Severity Categories

For the anthrax scenario, patients arrive at the hospital(s) in one of two conditions:

1. Mild: When victims become ill, they are more than 3 days away from death, assuming no treatment.
2. Severe: When victims become ill, they are 3 or fewer days away from death, assuming no treatment.

Users have the option of specifying either the number and type or simply the number of casualties who present at their hospital(s).

If the user specifies only the number of casualties, the model assumes the casualties arriving at the hospital(s) are distributed according to the table below:

Casualty Condition	Percent
Mild: When victims become ill, they are more than 3 days away from death, assuming no treatment.	79.8%
Severe: When victims become ill, they are 3 or fewer days away from death, assuming no treatment.	20.2%

This breakdown by casualty condition is based on work performed during development of the original Surge Model in 2005. In brief, plume modeling was used to estimate the distribution of anthrax spores for scenarios in several different cities. From this data, we modeled the estimated distribution of exposure for any major city. We used an average-sized American city as the basis for our estimates. Human and animal data were used to estimate the likely time of onset of symptoms. Given a mean time to death, casualties were normally distributed to have onset times greater or shorter than average. Patients with a very short "time to death" without treatment were termed "severe" and other patients "mild." Patients were expected to seek help at the onset of symptoms.

1.2. Casualty Arrival Pattern

Casualties are assumed to present at the hospital(s) when symptoms appear, which occurs over a period of several days. To determine the arrival pattern, we analyzed the distribution of mild and severe cases, using an average-sized city. The arrival pattern of casualties closely matched a gamma distribution, which was used to estimate the time of arrival for patients when both number and condition are specified.

1.3. Length of Stay By Hospital Unit

The assumed average length of stay (in days) of patients the ED, ICU, and the floor (based on reference no. 14 listed at the end of this section) are:

Average LOS by Hospital Unit	Mild case	Severe case
ED	1	1
Floor, not via ICU	22	22
Floor, via ICU	19	19
ICU	3	3

1.4. Path Probabilities and Lengths of Stay

The table below shows the assumed probabilities of different "paths" through the hospital(s) (based on reference no. 14 listed at the end of this section). The table shows, for example, that a patient presenting with a mild case of anthrax has a 21 percent chance of being transferred from the ED to the ICU and then dying in the ICU.

Path	Mild case	Severe case
ED → Discharge	5%	0%
ED → Death	0%	0%
ED → Floor → Discharge	46%	3%
ED → Floor → Death	11%	1%
ED → Floor → ICU → Death	11%	5%
ED → Floor → ICU → Floor → Discharge	1%	0%
ED → Floor → ICU → Floor → Death	1%	1%
ED → ICU → Death	21%	69%
ED → ICU → Floor → Discharge	2%	7%
ED → ICU → Floor → Death	1%	15%

The breakdown of length of stay by patient type summed across all paths is:

Average LOS by Patient Outcome	Mild case	Severe case
Survivors	21.23	23.43
Fatalities	8.08	5.01
Average Combined	15.30	6.80

1.5. Overall Outcome Probabilities

Based on these inputs (and reference no. 11 listed at the end of this section), the overall discharge and death probabilities are:

Outcome	Mild case	Severe case
Discharge	55%	10%
Death	45%	90%

1.6. Resources Consumed Per Patient Per Day

The assumed level of resource consumption per patient per day is shown in the table below:

Resource	Units	Category	Subcategory	Lambda1	Mild			Severe
					ED	ICU	Floor	ED	ICU	Floor
Med/Surg Bed	Unit of Use	Capacity	Floor	1	0.083	0	1	0.167	0	1
ICU Bed	Unit of Use	Capacity	ICU	1	0	1	0	0	1	0
Burn Bed	Unit of Use	Capacity	Burn	1	0	0	0	0	0	0
Operating Room	Unit of Use	Capacity	OR	1	0	0	0	0	0	0
Airborne Isolation Room	Unit of Use	Capacity	Isolation	0.9	0	0	0	0	0	0
Intensivists (CCM)	FTE	Staff	CCM	0.7	0.021	0.042	0	0.042	0.042	0
Critical care nurses (CCN)	FTE	Staff	CCN	1	0	0.33	0	0.167	0.33	0
Surgeons	FTE	Staff	Surgeon	0.3	0	0.042	0	0.042	0.042	0
Non-intensivists (MD)	FTE	Staff	MD	0.9	0.042	0	0.021	0.042	0	0.021
Non-critical care nurses (RN/LPN)	FTE	Staff	RN	1	0.167	0	0.146	0	0	0.146
Respiratory Therapists (RT)	FTE	Staff	RT	0.7	0	0.083	0	0.083	0.083	0
Radiology machines	Machine Time	Lab/Radiology	Radiology	0.3	0.021	0.021	0	0.021	0.021	0
Radiologic Technicians	FTE	Staff	Rad Tech	0.3	0.021	0.021	0	0.021	0.021	0
Pharmacists (PharmD/RPh)	FTE	Staff	Pharmacist	0.7	0.021	0.062	0.042	0.021	0.062	0.042
Mechanical ventilator	Machine Time	Capacity	Ventilator	0.9	0	0	0	1	1	0
Ventilator equipment	Unit of Use	Equipment	Vent Tubing	0.9	0	0	0	1	1	0
Oxygen (O2)	Unit of Use	Supplies	Oxygen	0.9	0	1	0	2	2	0
Oxygenation monitoring equipment	Machine Time	Equipment	O2 Monitoring	0.9	0.083	1	0	0.083	1	0.5
Surgical supplies	Unit of Use	Supplies	Surgical	0.3	0	0.25	0	0	0.025	0
Radiology supplies	Unit of Use	Supplies	Radiological	0.3	1	1	0	1	1	0
Cirprofloxacin or Doxycycline	400mg/100mg bid	Pharmacy	Antibiotics	1	1	1	1	1	1	1
Rifampin or other 2nd line agent	600mg po bid	Pharmacy	Antibiotics	1	0	1	0	1	1	1
Antibiotcs for Secondary Pneumonia	Assorted	Pharmacy	Antibiotics	1	0	0	0	0	1	0
Antibiotics intravenous infusion set	Unit of Use	Supplies	IV set	1	1	0.5	0.5	1	0.5	0.5
Hemodynamic medications	Unit of Use	Pharmacy	Hemodynamic	0.7	0	1	0	1	1	0
Intravenous fluids	Unit of Use	Pharmacy	IVF	0.7	1	1	0.5	1	1	1
Intravenous infusions set	Unit of Use	Supplies	IV Set	0.7	1	1	0.5	1	1	1
Laboratory machines	Machine Time	Lab/Radiology	Laboratory	0.7	0.021	0.021	0.021	0.021	0.042	0.021
Laboratory supplies	Unit of Use	Supplies	Laboratory	0.7	0.5	0.5	0.5	0.5	1	0.5
Temperature monitoring equipment	Machine Time	Equipment	Temperature	1	0.083	1	1	0.083	1	1
Thromboembolism prophylaxis	Unit of Use	Pharmacy	DVT Prophylaxis	1	0	1	0	0	1	1
Urine output monitoring equipment	Unit of Use	Equipment	U/O	1	0	1	0	0	1	0
Universal Precautions PPE	Unit of Use	PPE	Universal	1	1	1	1	1	1	1
Waste Disposal	Unit of Use	Waste Mgmt	Decon Waste	0.3	1	0	0	1	0	0
IV Steroids	Unit of Use	Pharmacy	Steroids	0.7	0	0	0	0	0	0
Enteral feedings (3/day/patient)	Unit of Use	Nutrition	Enteral	1	0	0.5	0	0	0.5	0
Oral food (3 meals per day per patient)	Unit of Use	Nutrition	Oral	1	0	0.5	1	0	0.5	1
Sheet change	Unit of Use	Housekeeping	Laundry	1	1	1	1	1	1	1
Patient infection control	FTE	Epidemiology	Infection Control	0.5	0.083	0.083	0.083	0.083	0.083	0.083
Engineering	FTE	Engineering	Facility	0.7	0.042	0.083	0.042	0.042	0.083	0.042
Janitorial/Housekeeping	FTE	Housekeeping	Janitorial	1	0.083	0.125	0.083	0.125	0.125	0.083
Nutrition	FTE	Nutrition	Counseling	0.5	0	0.083	0.083	0	0.083	0.083
Psychological support	FTE	Ancillary	Psychologist	0.5	0.021	0.042	0.042	0	0.042	0.042
Mortuary	FTE	Mortuary	Morgue	0.1	0	0.042	0.042	0	0.083	0.042

1. Lambda captures the resource requirement decay rate for a resource.  Lambda = 1 implies no decay; the patient requires a constant amount of the resource while s/he is hospitalized.  Lambda <1 implies that less of the resource is required each day the patient is hospitalized.  Go to section 2.2 for details.

1.7. References

1. A case of anthrax septicaemia in a London teaching hospital. Commun Dis Rep CDR Wkly 1995;5(36):169.

2. Barakat LA, Quentzel HL, Jernigan JA, et al. Fatal inhalational anthrax in a 94-year-old Connecticut woman. JAMA 2002;287(7):863-8.

3. Bartlett JG, Inglesby TV Jr., Borio L. Management of anthrax. Clin Infect Dis 2002;35(7):851-8.

4. Bell DM, Kozarsky PE, Stephens DS. Clinical issues in the prophylaxis, diagnosis, and treatment of anthrax. Emerg Infect Dis 2002;8(2):222-5.

5. Borio L, Frank D, Mani V, et al. Death due to bioterrorism-related inhalational anthrax: report of 2 patients. JAMA 2001;286(20):2554-9.

6. Cieslak TJ, Eitzen EM Jr. Clinical and epidemiologic principles of anthrax. Emerg Infect Dis 1999;5(4):552-5.

7. Darling RG, Catlett CL, Huebner KD, et al. Threats in bioterrorism. I: CDC category A agents. Emerg Med Clin North Am 2002;20(2):273-309.

8. Dewan PK, Fry AM, Laserson K, et al. Inhalational anthrax outbreak among postal workers, Washington, D.C., 2001. Emerg Infect Dis 2002;8(10):1066-72.

9. Felek S, Akbulut A, Kalkan A. A case of anthrax sepsis: non-fatal course. J Infect 1999;38(3):201-2.

10. Friedlander AM. Anthrax: clinical features, pathogenesis, and potential biological warfare threat. Curr Clin Top Infect Dis 2000;20:335-49.

11.Holty JE, Bravata DM, Liu H, et al. Systematic review: a century of inhalational anthrax cases from 1900 to 2005. Ann Intern Med 2006; 144(4):270-80.

12. Holtz TH, Ackelsberg J, Kool JL, et al. Isolated case of bioterrorism-related inhalational anthrax, New York City, 2001. Emerg Infect Dis 2003;9(6):689-96.

13. Inglesby TV, O'Toole T, Henderson DA, et al. Anthrax as a biological weapon, 2002: updated recommendations for management. JAMA 2002;287(17):2236-52.

14.Jernigan DB, Raghunathan PL, Bell BP, et al. Investigation of bioterrorism-related anthrax, United States, 2001: epidemiologic findings. Emerg Infect Dis 2002;8(10):1019-28.

15. Mayer TA, Bersoff-Matcha S, Murphy C, et al. Clinical presentation of inhalational anthrax following bioterrorism exposure: report of 2 surviving patients. JAMA 2001;286(20):2549-53.

16. Mina B, Dym JP, Kuepper F, et al. Fatal inhalational anthrax with unknown source of exposure in a 61-year- old woman in New York City. JAMA 2002;287(7):858-62.

17. Swartz MN. Recognition and management of anthrax—an update. N Engl J Med 2001;345(22):1621-6.

18. Traeger MS, Wiersma ST, Rosenstein NE, et al. First case of bioterrorism-related inhalational anthrax in the United States, Palm Beach County, Florida, 2001. Emerg Infect Dis 2002;8(10):1029-34.

19. Yetman RJ, Parks D, Taft E. Management of patients exposed to biologic weapons. J Pediatr Health Care 2002;16(5):256-61.

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