Epidemiologic Response to Anthrax Outbreaks: Field Investigations, 1950-2001

Michael E. Bales, Andrew L. Dannenberg, Philip S. Brachman, Arnold F. Kaufmann,Peter C. Klatsky, David A. Ashford

Emerging Infectious Diseases. 2002;8(10)

Abstract and Introduction

We used unpublished reports, published manuscripts, and communication with investigators to identify and summarize 49 anthrax-related epidemiologic field investigations conducted by the Centers for Disease Control and Prevention from 1950 to August 2001. Of 41 investigations in which Bacillus anthracis caused human or animal disease, 24 were in agricultural settings, 11 in textile mills, and 6 in other settings. Among the other investigations, two focused on building decontamination, one was a response to bioterrorism threats, and five involved other causes. Knowledge gained in these investigations helped guide the public health response to the October 2001 intentional release of B. anthracis, especially by addressing the management of anthrax threats, prevention of occupational anthrax, use of antibiotic prophylaxis in exposed persons, use of vaccination, spread of B. anthracis spores in aerosols, clinical diagnostic and laboratory confirmation methods, techniques for environmental sampling of exposed surfaces, and methods for decontaminating buildings.

The intentional release of Bacillus anthracis in October 2001 greatly challenged the U.S. public health system. Collaborating with partners in other federal, state, and local health agencies, the Centers for Disease Control and Prevention (CDC) responded to these bioterrorism events by relying on experience investigating public health aspects of anthrax over the past 50 years.^[1] Topics addressed in these investigations included epidemiology, vaccines,^[2,3] controlling anthrax in industrial and agricultural settings,^[4] public health response to bioterrorism events,^[5] B. anthracis contamination of milk and meat,^[6] identifying B. anthracis-contaminated commercial products,^[7] decontamination methods for contaminated environmental sites, and laboratory methods, among others.

Field studies conducted by the Epidemic Intelligence Service (EIS) constituted the cornerstone of these investigative efforts.^[8] When invited by a state health department or national ministry of health, CDC's EIS Officers conduct field investigations, Epidemic-Aids (known as Epi-Aids), in response to acute public health needs in the United States and other countries. Recently, historic documents from >4,000 Epi-Aids (approximately 90% domestic, 10% international) from 1950 to 1999 were made more accessible through the creation of an internal, searchable electronic database. It includes many unpublished CDC reports on early anthrax investigations, which form the basis of this report.

B. anthracis, the gram-positive, spore-forming, rod-shaped bacterium that causes anthrax,^[9] is most commonly a zoonotic pathogen. Human B. anthracis infections are rare in the United States; the number of cases has decreased steadily from an average of 35 reported cases per year in the 1950s to <1 reported case per year since 1980^[10,11] ( Table 1 ). Most reported cases have been cutaneous. Before October 2001, the last case of inhalational anthrax in the United States occurred in 1976 (12,13).

To answer questions raised when the bioterrorism-related cases of anthrax were identified in October 2001, we reviewed results of field investigations of anthrax. We also identified current questions for which past experience with anthrax provided relatively little information and for which further research is needed.

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Abstract and Introduction
Methods
Results
Discussion
Conclusion
References

Table 1. CDC field investigations of suspected anthrax in humans and animals, and reported cases of anthrax in humans, United States, 1950-2001 ^a
Years	Field investigations				No. of cases of anthrax in humans reported nationally^c
	No. of investigations^b	No. of human cases
	No. of investigations^b	Cutaneous	Inhalational	Total
1950-54	2	1	0	1	223
1955-59	11	16	6	22	131
1960-64	4	5	1	6	54
1965-69	7	5	1	6	21
1970-74	8	4	0	4	13
1975-79	6	5	1	6	10
1980-84	0	0	0	0	2
1985-89	1	1	0	1	3
1990-94	1	0	0	0	1
1995-99	2	0	0	0	0
2000-01^d	2	2	0	2	Not available
Total	44	39	9	48	458

Table 2. Characteristics of CDC field investigations of anthrax in humans and animals, 1950-August 2001 ^a
Year	Location	No. of cases		Reference	Comments
Year	Location	Human	Animal	Reference	Comments
Agricultural settings (n=24 investigations)
2001	TX (southwest)	1	1,638	Epi-Aid 2001-61	Large epizootic affecting 63 properties in five counties; members of at least 11 animal species were infected with Bacillus anthracis.
2000	ND (east)	1	Multiple	Epi-Aid 2000-69,^[14]	USDA recommended quarantine on affected premises, vaccinating livestock on surrounding premises, and burning and/or burying infected carcasses, bedding, and other nearby materials.
1998	Kazakhstan	≥53	Multiple	Epi-Aid 1998-83	Multivariate analysis found highest risk for cutaneous anthrax from slaughtering, butchering, and cutting B. anthracis-infected animals; eating cooked infected meat not an important risk factor.
1998	Uvalde, TX	One vaccine exposure	0	Epi-Aid 1998-55	Patient accidentally exposed to attenuated live anthrax vaccine while vaccinating horse, experienced severe myalgia and fatigue, then began antibiotic prophylaxis and recovered. Laboratory tests negative for B. anthracis.
1993	ND (southeast)	0	8	^[15]	NIOSH and USDA investigation following major flooding, anthrax in livestock, and soil contamination. Concern over contaminated water supply, but all water samples negative.
1986	Paraguay	≥21	0	Epi-Aid 1986-39,^[16]	Community outbreak of cutaneous anthrax in a remote village.
1979	Clay County, IA	0	16	Epi-Aid 1979-95	Raising chlorine level to 2 ppm eliminated two positive samples in well water. In local hospital records, no difference in number of gastrointestinal symptoms compared with same month in previous year.
1976	Foard and Cottle Counties, TX	0	At least 160	Epi-Aid 1976-115,^[17]	Significantly higher attack rates in bulls and horses; evidence against flies as important vector.
1974	Falls County, TX	0	At least 236	Epi-Aid 1975-6,^[18,19]	B. anthracis- positive sample from city water tap, so city water supply was hyperchlorinated. Soil samples collected to document efficacy of carcass incineration were negative.
1971	Danville, PA	0	33	Epi-Aid 1972-19	B. anthracis isolated from both hay and soil samples.
1971	Gonzales, LA	2	588	Epi-Aid 1971-131,^[3,20,21]	One culture positive and one negative in exposed veterinarians. Low attack rate in calves reduced likelihood that biting flies were an important vector.
1970	Yoder, WY	0	8	Epi-Aid 1971-44,^[22]	Veterinarian placed on antibiotic prophylaxis as a result of laceration while performing necropsy.
1968	Inyo County, CA	1	176	Epi-Aid 1969-20,^[23]	Extensive discussion and literature review of Tabanid species (horsefly) as potential vector; role in transmission remains inconclusive.
1968	Hampton, CT	0	3	Epi-Aid 1968-78	204 kg of B. anthracis-contaminated meat sold as hamburger before investigation. No human cases of anthrax known to have occurred as a result.
1965	Grand Forks, ND	0	19	Epi-Aid 1966-12,^[24]	30 diabetic children swam 3 miles downstream from where an animal was found dead from anthrax; riverborne spread determined minimal; prophylaxis considered unnecessary.
1962	MS	0	Multiple	Epi-Aid 1963-2	Involved many counties.
1959	Brownsville, Cameron County, TX	5	125	Epi-Aid 1960-12	Two cases laboratory confirmed. Cases occurred in three veterinarians and two other patients who had intimate contact during necropsy, handling, or skinning.
1959	NJ (south)	1	2 cows, many hogs	Epi-Aid 1959-38	Not laboratory confirmed. Several hogs developed illness after feeding on entrails of sick cows.
1958	LA (north)	0	15-20	Epi-Aid 1958-42	Involved cows, sheep, and horses.
1957	Vinita, OK	1	400-500	Epi-Aid 1958-11,^[25]	Large epizootic on farms curtailed after intensive immunization campaign.
1956	Saratoga, WY	0	Multiple	Epi-Aid 1957-17	Animal anthrax in mountainous area led to concern over water supply downstream.
1956	MS (northwest)	0	>250	Epi-Aid 1957-3	No evidence to support insectborne transmission, despite local beliefs. Involved 224 head of cattle, 42 mules, 5 horses, 3 sheep, 2 goats, multiple hogs. One case of suspected anthrax in a child was investigated and determined to be mumps.
1955	LA (southeast)	0	1,404	Epi-Aid 1955-5	Large epizootic in cattle. Unconfirmed reports of four human cases. B. anthracis isolated from flies in two instances at State Animal Disease Laboratory.
1952	OH (five counties)	0	Multiple	Epi-Aid 1952-13,^[26]	B. anthracis isolated from swine feed; contaminated bonemeal suspected as source of infections.
Textile mills (n=13 investigations)
1987	Charlotte, NC	1	0	Epi-Aid 1987-77,^[27]	Suspected cross-contamination of Australian wool from storage space shared with contaminated West Asian cashmere.
1978	NH (southeast)	2	0	Epi-Aid 1978-65	Patients did not wear protective equipment. One had systemic signs and symptoms (fever, headache, sore neck, malaise, anorexia) after his initial lesion was lanced. Subsequent full recovery.
1978	Shelby, NC	2	0	Epi-Aid 1978-47	Contents of vacuum cleaner bags or floor sweepings from four employee homes were collected; 1 tested positive for B. anthracis. 300 soil samples tested from mill premises, landfill site, and nearby residences. In mill, more positive samples in rooms where earliest processing occurred.
1974	Belton, SC	1	0	Epi-Aid 1974-77	Report suggested prevention should be based on minimizing contact between employees and contaminated material, and on routine vaccination of employees at risk. Patient not adequately vaccinated.
1972	Manchester, NH	N/A	N/A	Epi-Aid 1972-94	Effectiveness of formaldehyde vapor decontamination of B. anthracis spores assessed using spore strips in treated and untreated (control) areas of mill complex, and comparing pre- and posttreatment surface samples. No positives among 599 posttreatment specimens.
1967	Dillon, SC	N/A	N/A	^[28]	A building contaminated with B. anthracis was successfully decontaminated with formaldehyde vapor. 100,000 spores on 24 plates pretreatment were reduced to 21 sterile plates, and 3 plates with 2 colonies each, posttreatment. 26 of 142 surface swabs tested positive before decontamination, and 1 of 200 swabs tested positive 6 months after decontamination. Building was deemed safe for occupancy and no further cases were reported.
1966	Manchester, NH	2	0	Epi-Aid 1967-43	Patient with inhalational anthrax had history of "smoker's cough," diabetes, alcoholism, and chronic pancreatitis. Exposure believed to have occurred while patient worked for 4-5 hours directly opposite a goat hair-processing mill.
1961	Philadelphia, PA	1	0	Epi-Aid 1961-40;^[29]	After case reported, supplies of new and improved Wright vaccine sent to mill for use among employees.
1960	SC	4	0	Epi-Aid 1960-31,^[30]	All four cases responded well to antibiotic treatment.
1957	Philadelphia, PA	1	0	^[31,32]	Two additional inhalational cases mentioned that occurred over an 8-year period in persons living near the same contaminated tannery.
1957	Manchester, NH	9	0	Epi-Aid 1958-18,^{[33,34,35,36]}	Employees noted increased dust in air after initiating a new scouring technique in textile mill.
1956	Monroe, NC	≥5	0	Epi-Aid 1956-29,^[37]	Studies indicated heavy environmental contamination of mill with B. anthracis spores.
1953	Monroe, NC	1	0	Epi-Aid 1953-14	Nasal swabs of employees performed to assess exposure. No results available.
Other settings (n=7 investigations)
1998	CA, IN, KY, TN	0	0	Epi-Aid 1999-25,^[38]	Evaluation of multiple telephone threats and letters alleged to contain B. anthracis. Report included recommendations for response to bioterrorism threats.
1976	Morro Bay, CA	1	0	^[12,39,40]	Suspected source of anthrax in home craftsman was contaminated yarn imported from Pakistan. Multiple samples of yarn tested positive for B. anthracis. Subsequent CPSC warning on imported yarn.
1975	Camden, NJ	3	0	^[41,42,43]	Cutaneous anthrax in three gelatin manufacturing plant workers from contact with contaminated dry cattle bones; FDA recall of dicalcium phosphate animal feed product.
1974	Sequim, WA	0	42	^[44,45]	Several cougars and other large felines on private game farm died after feeding on infected horsemeat. Primary source: horse's saddle pad contained B. anthracis-contaminated goat hair from Afghanistan and Pakistan. Subsequent CPSC warning on contaminated saddle pads.
1974	Haiti; FL	1 in US; 194 in Haiti (1963-1974).	0	Epi-Aid 1974-96,^{[7,46,47,48,49,50]}	One human case in U.S.; 194 cases identified in Haiti in 1963-1974. 72 (25%) of 287 Haitian goatskin handicrafts tested from January to May 1974 were culture positive for B. anthracis, including voodoo balancing dolls, rugs, whole skins, mosaic pictures, purses, and drums. Subsequent CPSC warning on contaminated Haitian goatskin products.
1966	Manchester, NH	1	0	Epi-Aid 1967-43-3	Source of cutaneous infection in housewife unknown, but knitting yarn could not be ruled out. Three samples from knitted sweater positive for B. anthracis; samples from other sources negative.
1964	Oxford, OH	1	0	^[51,52]	Fatal cutaneous anthrax in installer of pipe insulation made with imported goat hair. Insulation and goat hair samples tested positive for B. anthracis.
Suspected anthrax shown due to other causes (n=5 investigations)
1975	Yavapai County, AZ	1	0	Epi-Aid 1975-115	23-year-old male machinist initially thought to have anthrax but quickly determined to have plague.
1969	Casper, WY	1	0	Epi-Aid 1969-78	Meat packing company employee; anthrax thought not to be responsible.
1967	Nepal	26	Multiple	Epi-Aid 1968-34	Community outbreak of cutaneous disease; subsequently diagnosed as plague.
1965	Charleston, SC	1	0	Epi-Aid 1966-18,^[53]	Cutaneous disease in customs inspector; B. anthracis not implicated.
1957	Jamestown, NY	5	0	Epi-Aid 1958-16	Cutaneous disease in butchers; later believed to be a streptococcal or staphylococcal infection.

Table 1. CDC field investigations of suspected anthrax in humans and animals, and reported cases of anthrax in humans, United States, 1950-2001 ^a
Years	Field investigations				No. of cases of anthrax in humans reported nationally^c
	No. of investigations^b	No. of human cases
	No. of investigations^b	Cutaneous	Inhalational	Total
1950-54	2	1	0	1	223
1955-59	11	16	6	22	131
1960-64	4	5	1	6	54
1965-69	7	5	1	6	21
1970-74	8	4	0	4	13
1975-79	6	5	1	6	10
1980-84	0	0	0	0	2
1985-89	1	1	0	1	3
1990-94	1	0	0	0	1
1995-99	2	0	0	0	0
2000-01^d	2	2	0	2	Not available
Total	44	39	9	48	458

Table 1. CDC field investigations of suspected anthrax in humans and animals, and reported cases of anthrax in humans, United States, 1950-2001 ^a
Years	Field investigations				No. of cases of anthrax in humans reported nationally^c
	No. of investigations^b	No. of human cases
	No. of investigations^b	Cutaneous	Inhalational	Total
1950-54	2	1	0	1	223
1955-59	11	16	6	22	131
1960-64	4	5	1	6	54
1965-69	7	5	1	6	21
1970-74	8	4	0	4	13
1975-79	6	5	1	6	10
1980-84	0	0	0	0	2
1985-89	1	1	0	1	3
1990-94	1	0	0	0	1
1995-99	2	0	0	0	0
2000-01^d	2	2	0	2	Not available
Total	44	39	9	48	458

Table 2. Characteristics of CDC field investigations of anthrax in humans and animals, 1950-August 2001 ^a
Year	Location	No. of cases		Reference	Comments
Year	Location	Human	Animal	Reference	Comments
Agricultural settings (n=24 investigations)
2001	TX (southwest)	1	1,638	Epi-Aid 2001-61	Large epizootic affecting 63 properties in five counties; members of at least 11 animal species were infected with Bacillus anthracis.
2000	ND (east)	1	Multiple	Epi-Aid 2000-69,^[14]	USDA recommended quarantine on affected premises, vaccinating livestock on surrounding premises, and burning and/or burying infected carcasses, bedding, and other nearby materials.
1998	Kazakhstan	≥53	Multiple	Epi-Aid 1998-83	Multivariate analysis found highest risk for cutaneous anthrax from slaughtering, butchering, and cutting B. anthracis-infected animals; eating cooked infected meat not an important risk factor.
1998	Uvalde, TX	One vaccine exposure	0	Epi-Aid 1998-55	Patient accidentally exposed to attenuated live anthrax vaccine while vaccinating horse, experienced severe myalgia and fatigue, then began antibiotic prophylaxis and recovered. Laboratory tests negative for B. anthracis.
1993	ND (southeast)	0	8	^[15]	NIOSH and USDA investigation following major flooding, anthrax in livestock, and soil contamination. Concern over contaminated water supply, but all water samples negative.
1986	Paraguay	≥21	0	Epi-Aid 1986-39,^[16]	Community outbreak of cutaneous anthrax in a remote village.
1979	Clay County, IA	0	16	Epi-Aid 1979-95	Raising chlorine level to 2 ppm eliminated two positive samples in well water. In local hospital records, no difference in number of gastrointestinal symptoms compared with same month in previous year.
1976	Foard and Cottle Counties, TX	0	At least 160	Epi-Aid 1976-115,^[17]	Significantly higher attack rates in bulls and horses; evidence against flies as important vector.
1974	Falls County, TX	0	At least 236	Epi-Aid 1975-6,^[18,19]	B. anthracis- positive sample from city water tap, so city water supply was hyperchlorinated. Soil samples collected to document efficacy of carcass incineration were negative.
1971	Danville, PA	0	33	Epi-Aid 1972-19	B. anthracis isolated from both hay and soil samples.
1971	Gonzales, LA	2	588	Epi-Aid 1971-131,^[3,20,21]	One culture positive and one negative in exposed veterinarians. Low attack rate in calves reduced likelihood that biting flies were an important vector.
1970	Yoder, WY	0	8	Epi-Aid 1971-44,^[22]	Veterinarian placed on antibiotic prophylaxis as a result of laceration while performing necropsy.
1968	Inyo County, CA	1	176	Epi-Aid 1969-20,^[23]	Extensive discussion and literature review of Tabanid species (horsefly) as potential vector; role in transmission remains inconclusive.
1968	Hampton, CT	0	3	Epi-Aid 1968-78	204 kg of B. anthracis-contaminated meat sold as hamburger before investigation. No human cases of anthrax known to have occurred as a result.
1965	Grand Forks, ND	0	19	Epi-Aid 1966-12,^[24]	30 diabetic children swam 3 miles downstream from where an animal was found dead from anthrax; riverborne spread determined minimal; prophylaxis considered unnecessary.
1962	MS	0	Multiple	Epi-Aid 1963-2	Involved many counties.
1959	Brownsville, Cameron County, TX	5	125	Epi-Aid 1960-12	Two cases laboratory confirmed. Cases occurred in three veterinarians and two other patients who had intimate contact during necropsy, handling, or skinning.
1959	NJ (south)	1	2 cows, many hogs	Epi-Aid 1959-38	Not laboratory confirmed. Several hogs developed illness after feeding on entrails of sick cows.
1958	LA (north)	0	15-20	Epi-Aid 1958-42	Involved cows, sheep, and horses.
1957	Vinita, OK	1	400-500	Epi-Aid 1958-11,^[25]	Large epizootic on farms curtailed after intensive immunization campaign.
1956	Saratoga, WY	0	Multiple	Epi-Aid 1957-17	Animal anthrax in mountainous area led to concern over water supply downstream.
1956	MS (northwest)	0	>250	Epi-Aid 1957-3	No evidence to support insectborne transmission, despite local beliefs. Involved 224 head of cattle, 42 mules, 5 horses, 3 sheep, 2 goats, multiple hogs. One case of suspected anthrax in a child was investigated and determined to be mumps.
1955	LA (southeast)	0	1,404	Epi-Aid 1955-5	Large epizootic in cattle. Unconfirmed reports of four human cases. B. anthracis isolated from flies in two instances at State Animal Disease Laboratory.
1952	OH (five counties)	0	Multiple	Epi-Aid 1952-13,^[26]	B. anthracis isolated from swine feed; contaminated bonemeal suspected as source of infections.
Textile mills (n=13 investigations)
1987	Charlotte, NC	1	0	Epi-Aid 1987-77,^[27]	Suspected cross-contamination of Australian wool from storage space shared with contaminated West Asian cashmere.
1978	NH (southeast)	2	0	Epi-Aid 1978-65	Patients did not wear protective equipment. One had systemic signs and symptoms (fever, headache, sore neck, malaise, anorexia) after his initial lesion was lanced. Subsequent full recovery.
1978	Shelby, NC	2	0	Epi-Aid 1978-47	Contents of vacuum cleaner bags or floor sweepings from four employee homes were collected; 1 tested positive for B. anthracis. 300 soil samples tested from mill premises, landfill site, and nearby residences. In mill, more positive samples in rooms where earliest processing occurred.
1974	Belton, SC	1	0	Epi-Aid 1974-77	Report suggested prevention should be based on minimizing contact between employees and contaminated material, and on routine vaccination of employees at risk. Patient not adequately vaccinated.
1972	Manchester, NH	N/A	N/A	Epi-Aid 1972-94	Effectiveness of formaldehyde vapor decontamination of B. anthracis spores assessed using spore strips in treated and untreated (control) areas of mill complex, and comparing pre- and posttreatment surface samples. No positives among 599 posttreatment specimens.
1967	Dillon, SC	N/A	N/A	^[28]	A building contaminated with B. anthracis was successfully decontaminated with formaldehyde vapor. 100,000 spores on 24 plates pretreatment were reduced to 21 sterile plates, and 3 plates with 2 colonies each, posttreatment. 26 of 142 surface swabs tested positive before decontamination, and 1 of 200 swabs tested positive 6 months after decontamination. Building was deemed safe for occupancy and no further cases were reported.
1966	Manchester, NH	2	0	Epi-Aid 1967-43	Patient with inhalational anthrax had history of "smoker's cough," diabetes, alcoholism, and chronic pancreatitis. Exposure believed to have occurred while patient worked for 4-5 hours directly opposite a goat hair-processing mill.
1961	Philadelphia, PA	1	0	Epi-Aid 1961-40;^[29]	After case reported, supplies of new and improved Wright vaccine sent to mill for use among employees.
1960	SC	4	0	Epi-Aid 1960-31,^[30]	All four cases responded well to antibiotic treatment.
1957	Philadelphia, PA	1	0	^[31,32]	Two additional inhalational cases mentioned that occurred over an 8-year period in persons living near the same contaminated tannery.
1957	Manchester, NH	9	0	Epi-Aid 1958-18,^{[33,34,35,36]}	Employees noted increased dust in air after initiating a new scouring technique in textile mill.
1956	Monroe, NC	≥5	0	Epi-Aid 1956-29,^[37]	Studies indicated heavy environmental contamination of mill with B. anthracis spores.
1953	Monroe, NC	1	0	Epi-Aid 1953-14	Nasal swabs of employees performed to assess exposure. No results available.
Other settings (n=7 investigations)
1998	CA, IN, KY, TN	0	0	Epi-Aid 1999-25,^[38]	Evaluation of multiple telephone threats and letters alleged to contain B. anthracis. Report included recommendations for response to bioterrorism threats.
1976	Morro Bay, CA	1	0	^[12,39,40]	Suspected source of anthrax in home craftsman was contaminated yarn imported from Pakistan. Multiple samples of yarn tested positive for B. anthracis. Subsequent CPSC warning on imported yarn.
1975	Camden, NJ	3	0	^[41,42,43]	Cutaneous anthrax in three gelatin manufacturing plant workers from contact with contaminated dry cattle bones; FDA recall of dicalcium phosphate animal feed product.
1974	Sequim, WA	0	42	^[44,45]	Several cougars and other large felines on private game farm died after feeding on infected horsemeat. Primary source: horse's saddle pad contained B. anthracis-contaminated goat hair from Afghanistan and Pakistan. Subsequent CPSC warning on contaminated saddle pads.
1974	Haiti; FL	1 in US; 194 in Haiti (1963-1974).	0	Epi-Aid 1974-96,^{[7,46,47,48,49,50]}	One human case in U.S.; 194 cases identified in Haiti in 1963-1974. 72 (25%) of 287 Haitian goatskin handicrafts tested from January to May 1974 were culture positive for B. anthracis, including voodoo balancing dolls, rugs, whole skins, mosaic pictures, purses, and drums. Subsequent CPSC warning on contaminated Haitian goatskin products.
1966	Manchester, NH	1	0	Epi-Aid 1967-43-3	Source of cutaneous infection in housewife unknown, but knitting yarn could not be ruled out. Three samples from knitted sweater positive for B. anthracis; samples from other sources negative.
1964	Oxford, OH	1	0	^[51,52]	Fatal cutaneous anthrax in installer of pipe insulation made with imported goat hair. Insulation and goat hair samples tested positive for B. anthracis.
Suspected anthrax shown due to other causes (n=5 investigations)
1975	Yavapai County, AZ	1	0	Epi-Aid 1975-115	23-year-old male machinist initially thought to have anthrax but quickly determined to have plague.
1969	Casper, WY	1	0	Epi-Aid 1969-78	Meat packing company employee; anthrax thought not to be responsible.
1967	Nepal	26	Multiple	Epi-Aid 1968-34	Community outbreak of cutaneous disease; subsequently diagnosed as plague.
1965	Charleston, SC	1	0	Epi-Aid 1966-18,^[53]	Cutaneous disease in customs inspector; B. anthracis not implicated.
1957	Jamestown, NY	5	0	Epi-Aid 1958-16	Cutaneous disease in butchers; later believed to be a streptococcal or staphylococcal infection.

Table 2. Characteristics of CDC field investigations of anthrax in humans and animals, 1950-August 2001 ^a
Year	Location	No. of cases		Reference	Comments
Year	Location	Human	Animal	Reference	Comments
Agricultural settings (n=24 investigations)
2001	TX (southwest)	1	1,638	Epi-Aid 2001-61	Large epizootic affecting 63 properties in five counties; members of at least 11 animal species were infected with Bacillus anthracis.
2000	ND (east)	1	Multiple	Epi-Aid 2000-69,^[14]	USDA recommended quarantine on affected premises, vaccinating livestock on surrounding premises, and burning and/or burying infected carcasses, bedding, and other nearby materials.
1998	Kazakhstan	≥53	Multiple	Epi-Aid 1998-83	Multivariate analysis found highest risk for cutaneous anthrax from slaughtering, butchering, and cutting B. anthracis-infected animals; eating cooked infected meat not an important risk factor.
1998	Uvalde, TX	One vaccine exposure	0	Epi-Aid 1998-55	Patient accidentally exposed to attenuated live anthrax vaccine while vaccinating horse, experienced severe myalgia and fatigue, then began antibiotic prophylaxis and recovered. Laboratory tests negative for B. anthracis.
1993	ND (southeast)	0	8	^[15]	NIOSH and USDA investigation following major flooding, anthrax in livestock, and soil contamination. Concern over contaminated water supply, but all water samples negative.
1986	Paraguay	≥21	0	Epi-Aid 1986-39,^[16]	Community outbreak of cutaneous anthrax in a remote village.
1979	Clay County, IA	0	16	Epi-Aid 1979-95	Raising chlorine level to 2 ppm eliminated two positive samples in well water. In local hospital records, no difference in number of gastrointestinal symptoms compared with same month in previous year.
1976	Foard and Cottle Counties, TX	0	At least 160	Epi-Aid 1976-115,^[17]	Significantly higher attack rates in bulls and horses; evidence against flies as important vector.
1974	Falls County, TX	0	At least 236	Epi-Aid 1975-6,^[18,19]	B. anthracis- positive sample from city water tap, so city water supply was hyperchlorinated. Soil samples collected to document efficacy of carcass incineration were negative.
1971	Danville, PA	0	33	Epi-Aid 1972-19	B. anthracis isolated from both hay and soil samples.
1971	Gonzales, LA	2	588	Epi-Aid 1971-131,^[3,20,21]	One culture positive and one negative in exposed veterinarians. Low attack rate in calves reduced likelihood that biting flies were an important vector.
1970	Yoder, WY	0	8	Epi-Aid 1971-44,^[22]	Veterinarian placed on antibiotic prophylaxis as a result of laceration while performing necropsy.
1968	Inyo County, CA	1	176	Epi-Aid 1969-20,^[23]	Extensive discussion and literature review of Tabanid species (horsefly) as potential vector; role in transmission remains inconclusive.
1968	Hampton, CT	0	3	Epi-Aid 1968-78	204 kg of B. anthracis-contaminated meat sold as hamburger before investigation. No human cases of anthrax known to have occurred as a result.
1965	Grand Forks, ND	0	19	Epi-Aid 1966-12,^[24]	30 diabetic children swam 3 miles downstream from where an animal was found dead from anthrax; riverborne spread determined minimal; prophylaxis considered unnecessary.
1962	MS	0	Multiple	Epi-Aid 1963-2	Involved many counties.
1959	Brownsville, Cameron County, TX	5	125	Epi-Aid 1960-12	Two cases laboratory confirmed. Cases occurred in three veterinarians and two other patients who had intimate contact during necropsy, handling, or skinning.
1959	NJ (south)	1	2 cows, many hogs	Epi-Aid 1959-38	Not laboratory confirmed. Several hogs developed illness after feeding on entrails of sick cows.
1958	LA (north)	0	15-20	Epi-Aid 1958-42	Involved cows, sheep, and horses.
1957	Vinita, OK	1	400-500	Epi-Aid 1958-11,^[25]	Large epizootic on farms curtailed after intensive immunization campaign.
1956	Saratoga, WY	0	Multiple	Epi-Aid 1957-17	Animal anthrax in mountainous area led to concern over water supply downstream.
1956	MS (northwest)	0	>250	Epi-Aid 1957-3	No evidence to support insectborne transmission, despite local beliefs. Involved 224 head of cattle, 42 mules, 5 horses, 3 sheep, 2 goats, multiple hogs. One case of suspected anthrax in a child was investigated and determined to be mumps.
1955	LA (southeast)	0	1,404	Epi-Aid 1955-5	Large epizootic in cattle. Unconfirmed reports of four human cases. B. anthracis isolated from flies in two instances at State Animal Disease Laboratory.
1952	OH (five counties)	0	Multiple	Epi-Aid 1952-13,^[26]	B. anthracis isolated from swine feed; contaminated bonemeal suspected as source of infections.
Textile mills (n=13 investigations)
1987	Charlotte, NC	1	0	Epi-Aid 1987-77,^[27]	Suspected cross-contamination of Australian wool from storage space shared with contaminated West Asian cashmere.
1978	NH (southeast)	2	0	Epi-Aid 1978-65	Patients did not wear protective equipment. One had systemic signs and symptoms (fever, headache, sore neck, malaise, anorexia) after his initial lesion was lanced. Subsequent full recovery.
1978	Shelby, NC	2	0	Epi-Aid 1978-47	Contents of vacuum cleaner bags or floor sweepings from four employee homes were collected; 1 tested positive for B. anthracis. 300 soil samples tested from mill premises, landfill site, and nearby residences. In mill, more positive samples in rooms where earliest processing occurred.
1974	Belton, SC	1	0	Epi-Aid 1974-77	Report suggested prevention should be based on minimizing contact between employees and contaminated material, and on routine vaccination of employees at risk. Patient not adequately vaccinated.
1972	Manchester, NH	N/A	N/A	Epi-Aid 1972-94	Effectiveness of formaldehyde vapor decontamination of B. anthracis spores assessed using spore strips in treated and untreated (control) areas of mill complex, and comparing pre- and posttreatment surface samples. No positives among 599 posttreatment specimens.
1967	Dillon, SC	N/A	N/A	^[28]	A building contaminated with B. anthracis was successfully decontaminated with formaldehyde vapor. 100,000 spores on 24 plates pretreatment were reduced to 21 sterile plates, and 3 plates with 2 colonies each, posttreatment. 26 of 142 surface swabs tested positive before decontamination, and 1 of 200 swabs tested positive 6 months after decontamination. Building was deemed safe for occupancy and no further cases were reported.
1966	Manchester, NH	2	0	Epi-Aid 1967-43	Patient with inhalational anthrax had history of "smoker's cough," diabetes, alcoholism, and chronic pancreatitis. Exposure believed to have occurred while patient worked for 4-5 hours directly opposite a goat hair-processing mill.
1961	Philadelphia, PA	1	0	Epi-Aid 1961-40;^[29]	After case reported, supplies of new and improved Wright vaccine sent to mill for use among employees.
1960	SC	4	0	Epi-Aid 1960-31,^[30]	All four cases responded well to antibiotic treatment.
1957	Philadelphia, PA	1	0	^[31,32]	Two additional inhalational cases mentioned that occurred over an 8-year period in persons living near the same contaminated tannery.
1957	Manchester, NH	9	0	Epi-Aid 1958-18,^{[33,34,35,36]}	Employees noted increased dust in air after initiating a new scouring technique in textile mill.
1956	Monroe, NC	≥5	0	Epi-Aid 1956-29,^[37]	Studies indicated heavy environmental contamination of mill with B. anthracis spores.
1953	Monroe, NC	1	0	Epi-Aid 1953-14	Nasal swabs of employees performed to assess exposure. No results available.
Other settings (n=7 investigations)
1998	CA, IN, KY, TN	0	0	Epi-Aid 1999-25,^[38]	Evaluation of multiple telephone threats and letters alleged to contain B. anthracis. Report included recommendations for response to bioterrorism threats.
1976	Morro Bay, CA	1	0	^[12,39,40]	Suspected source of anthrax in home craftsman was contaminated yarn imported from Pakistan. Multiple samples of yarn tested positive for B. anthracis. Subsequent CPSC warning on imported yarn.
1975	Camden, NJ	3	0	^[41,42,43]	Cutaneous anthrax in three gelatin manufacturing plant workers from contact with contaminated dry cattle bones; FDA recall of dicalcium phosphate animal feed product.
1974	Sequim, WA	0	42	^[44,45]	Several cougars and other large felines on private game farm died after feeding on infected horsemeat. Primary source: horse's saddle pad contained B. anthracis-contaminated goat hair from Afghanistan and Pakistan. Subsequent CPSC warning on contaminated saddle pads.
1974	Haiti; FL	1 in US; 194 in Haiti (1963-1974).	0	Epi-Aid 1974-96,^{[7,46,47,48,49,50]}	One human case in U.S.; 194 cases identified in Haiti in 1963-1974. 72 (25%) of 287 Haitian goatskin handicrafts tested from January to May 1974 were culture positive for B. anthracis, including voodoo balancing dolls, rugs, whole skins, mosaic pictures, purses, and drums. Subsequent CPSC warning on contaminated Haitian goatskin products.
1966	Manchester, NH	1	0	Epi-Aid 1967-43-3	Source of cutaneous infection in housewife unknown, but knitting yarn could not be ruled out. Three samples from knitted sweater positive for B. anthracis; samples from other sources negative.
1964	Oxford, OH	1	0	^[51,52]	Fatal cutaneous anthrax in installer of pipe insulation made with imported goat hair. Insulation and goat hair samples tested positive for B. anthracis.
Suspected anthrax shown due to other causes (n=5 investigations)
1975	Yavapai County, AZ	1	0	Epi-Aid 1975-115	23-year-old male machinist initially thought to have anthrax but quickly determined to have plague.
1969	Casper, WY	1	0	Epi-Aid 1969-78	Meat packing company employee; anthrax thought not to be responsible.
1967	Nepal	26	Multiple	Epi-Aid 1968-34	Community outbreak of cutaneous disease; subsequently diagnosed as plague.
1965	Charleston, SC	1	0	Epi-Aid 1966-18,^[53]	Cutaneous disease in customs inspector; B. anthracis not implicated.
1957	Jamestown, NY	5	0	Epi-Aid 1958-16	Cutaneous disease in butchers; later believed to be a streptococcal or staphylococcal infection.

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