level of the 49 controls was 5 ppt (median, 5 ppt); 2% (1 person) had a level above 20 ppt. Additionally, 79% of the Ranch Hand personnel and 2% of the controls had TCDD levels at or above 10 ppt (chi-square test, p<0.0001). The five highest TCDD levels in the Ranch Hand group were 201, 210, 211, 303, and 313 ppt. The one control who had a level greater than 20 ppt (21.3 ppt) reported exposure to industrial chemicals since 1980 in a steel foundry in Indiana. Reported by: COL WH Wolfe, MD, MPH, JE Michalek, PhD, LTC JC Miner, DVM, MPH, LTC MR Petersen, DVM, MPH, DrPH, US Air Force, Brooks Air Force Base, Texas. Toxicology Br, Div of Environmental Health Laboratory Sciences, Center for Environmental Health and Injury Control, CDC. Editorial Note: The serum TCDD measurement provides a direct assessment of exposure. The distribution of TCDD levels in this phase of the Air Force Health Study indicates that some Ranch Hand personnel had unusually heavy TCDD exposure. The one control who had a TCDD level above background level had been exposed to industrial chemicals in the recent past. No threshold level has been determined as yet for the health effects of TCDD in humans. The half-life of TCDD in humans has been calculated as approximately 7 years (8) on the basis of TCDD levels in serum samples taken in 1982 and 1987 from 36 of the Ranch Hand personnel who had TCDD levels above 10 ppt in 1987. A half-life of 7 years suggests that only about two to four TCDD half-lives have elapsed since potential exposure of Ranch Hand personnel in Vietnam and that serum TCDD can serve as a biological marker for previous TCDD exposure of Air Force Health Study participants. A report on the entire 1987-1988 Air Force Health Study will be published after TCDD measurements have been completed for all participants and after the report has been reviewed by the Agent Orange Working Group of the Domestic Policy Council (Executive Branch). The result of the half-life study will be reported in a separate publication. References 1. Lathrop GD, Wolfe WH, Albanese RA, Moynahan PM. Epidemiologic investigation of health effects in Air Force personnel following exposure to herbicides: study protocol. Brooks Air Force Base, Texas: USAF School of Aerospace Medicine, 1982; National Technical Information Service document no. AD A 122 250. 2. Lathrop GD, Wolfe WH, Albanese RA, Moynahan PM. An epidemiologic investigation of health effects in Air Force personnel following exposure to herbicides: baseline morbidity study results. Brooks Air Force Base, Texas: USAF School of Aerospace Medicine, 1984; National Technical Information Service document no. AD A 138 340. 3. Lathrop GD, Machado SG, Karrison TG, et al. Air Force Health Study: an epidemiologic investigation of health effects in Air Force personnel following exposure to herbicides: final report. Brooks Air Force Base, Texas: USAF School of Aerospace Medicine, 1987; National Technical Information Services document no. AD A 188 262. 4. Patterson DG Jr, Hampton L, Lapeza CR Jr, et al. High-resolution gas chromatographic/highresolution mass spectrometric analysis of human serum on a whole-weight and lipid basis for 2,3,7,8-tetrachlorodibenzo-p-dioxin. Anal Chem 1987;59:2000-5. 5. Patterson DG Jr, Needham LL, Pirkle JL, et al. Correlation between serum and adipose tissue levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin in 50 persons from Missouri. Arch Environ Contam Toxicol 1988;17:139-43. 6. Centers for Disease Control. Serum dioxin in Vietnam-era veterans-preliminary report. MMWR 1987;36:470-5. 7. Byard JL. The toxicological significance of 2,3,7,8-tetrachlorodibenzo-p-dioxin and related compounds in human adipose tissue. J Toxicol Environ Health 1987;22:381-403. 8. Pirkle JL, Wolfe WH, Patterson DG Jr, et al. Estimates of the half-life of 2,3,7,8tetrachlorodibenzo-p-dioxin in Ranch Hand veterans. Presented at Dioxin '87, Las Vegas, Nevada, October 4-9, 1987. International Notes Cave-Associated Histoplasmosis Costa Rica An outbreak of histoplasmosis occurred among a group of university students who entered a cave in Santa Rosa National Park, Guanacaste Province, Costa Rica, on January 4, 1988. The cave was inhabited by about 500 bats, including three species of fruit bats (Glossophaga soricina, Carollia perspicillata, and Carollia subrufra) and one species of vampire bats (Desmodus rotundus). The cave consisted of two entrances to a single chamber 20 x 75 x 5 feet in size. Bat guano covered the floor of the cave, and the ground was noted to be exceptionally dry for the season. Seventeen students (mean age, 24 years; range, 20-40 years) entered the cave to observe the bats and photograph a small boa constrictor feeding on them. The students were in the cave an average of 26 minutes (range, 3–90 minutes). Fifteen (88%) of the 17 students became acutely ill within 9-24 days (mean, 14.4 days);* 12 remained ill 14 days after onset of symptoms. One student, who did not enter the cave, did not become ill. Signs and symptoms among the 15 ill persons included fever (93%), headache (87%), cough (80%), dyspnea (80%), chest pain (73%); and myalgia (53%). Two patients were hospitalized, but all recovered without antifungal treatment. Chest x-rays were obtained for 12 of the 15 patients; 10 had bilateral diffuse fluffy nodular parenchymal infiltrates. Late acute-phase and early convalescent-phase serum specimens (3 and 5 weeks after exposure to the cave) and urine specimens (5 weeks after exposure) were obtained from all 15 patients. Twelve of the 15 patients had evidence of histoplasmosis by complement fixation test, immunodiffusion test, or urinary antigen detection test (1,2). Reported by: JE Johnson, RN, BSN, JD Kabler, MD, Univ Health Svc, Univ of WisconsinMadison; MF Gourley, MD, DJ D'Alessio, MD, Univ of Wisconsin-Madison Medical School; RW Dodge, MS, R Golubjatnikov, PhD, Wisconsin State Laboratory of Hygiene; JP Davis, MD, State Epidemiologist, Wisconsin Dept of Health and Social Svcs. LJ Wheat, MD, Indiana Univ School of Medicine, Indianapolis. DH Janzen, PhD, Univ of Pennsylvania, Philadelphia. Pan American Health Organization. Div of Field Svcs, Epidemiology Program Office; Immunology Br, Div of Mycotic Diseases, Center for Infectious Diseases; Respiratory Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases, CDC. Editorial Note: Histoplasmosis is caused by inhalation of spores of Histoplasma capsulatum from its natural soil habitat. Growth of H. capsulatum requires moderate temperatures, high humidity, and a source of nitrates, often from decomposing feces of bats or birds. H. capsulatum has been isolated from both bat caves and bird roosts, and human infection has been associated with exposure to both sources (3). This outbreak is typical of bat-cave-associated histoplasmosis (4). The high attack rate (88%) could be explained by the relatively young age of the persons entering the cave or by exposure to a large inoculum of H. capsulatum spores. The extraordinarily dry ground in the cave also may have increased the dispersion of spores in the cave. H. capsulatum has been more readily isolated from caves under dry conditions than after flooding (5). Cave-acquired histoplasmosis differs in several respects from histoplasmosis associated with bird roosts. Bats, unlike avian species, may become infected with H. capsulatum (6). Therefore, formaldehyde spraying, a useful control measure for *A tour member who experienced any two of the following symptoms within 30 days after returning to the United States was considered to have histoplasmosis: fever, headache, cough, dyspnea, or chest pain. avian-associated sources of histoplasmosis (7), may be ineffective in reducing the risk of infection in a bat cave because bats can recontaminate the cave. Furthermore, skin test surveys have shown that persons living near contaminated caves have a lower prevalence of reactivity to histoplasmin than spelunkers living in the same area (3). This finding suggests that H. capsulatum infection occurs only in persons who enter contaminated caves. In contrast, airborne dispersal of organisms from bird roosts can cause outbreaks involving at least several square kilometers (8). Much of Santa Rosa National Park consists of mature deciduous dry forest in the relatively dry climate of northwest Costa Rica. During the rainy season (June-November), a seasonal river usually floods the cave that was associated with this outbreak and washes out the bat guano. However, flooding had not occurred because of extraordinarily low rainfall during this year's rainy season. Measured rainfall since 1978 has averaged 160 cm per year, but only 50-70 cm were recorded during 1987. The cave is accessible from a hiking trail and is commonly included on tours of the park led by local field biologists. No illness was reported among groups from the same university who entered the cave in January 1983 and January 1986. Officials of Santa Rosa National Park and field biologists in the area have been notified of the outbreak, and warning signs have been posted outside the cave. References 1. Kaufman L, Reiss E. Serodiagnosis of fungal diseases. In: Lennette EH, Balows A, Hausler WJ Jr, Shadomy HJ, eds. Manual of clinical microbiology. 4th ed. Washington, DC: American Society for Microbiology, 1985:924-44. 2. Wheat LJ, Kohler RB, Tewari RP. Diagnosis of disseminated histoplasmosis by detection of Histoplasma capsulatum antigen in serum and urine specimens. N Engl J Med 1986; 314:83-8. 3. Larsh HW. The epidemiology of histoplasmosis. In: Al-Doory Y, ed. The epidemiology of human mycotic diseases. Springfield, Illinois: Charles C Thomas, 1975:52-73. 4. Sacks JJ, Ajello L, Crockett LK. An outbreak and review of cave-associated histoplasmosis capsulati. J Med Vet Mycol 1986;24:313-25. 5. DiSalvo AF, Bigler WJ, Ajello L, Johnson JE, Palmer J. Bat and soil studies for sources of histoplasmosis in Florida. Public Health Rep 1970;85:1063-9. 6. Emmons CW, Klite PD, Baer GM, Hill WB Jr. Isolation of Histoplasma capsulatum from bats in the United States. Am J Epidemiol 1966;84:103-9. 7. Centers for Disease Control. Histoplasmosis control: decontamination of bird roosts, chicken houses, and other point sources. Atlanta: US Department of Health, Education, and Welfare, Public Health Service, 1979; HEW publication no. (CDC)80-8380. 8. DiSalvo AF, Johnson WM. Histoplasmosis in South Carolina: support for the microfocus concept. Am J Epidemiol 1979;109:480-92. Progress in Chronic Disease Prevention State- and Sex-Specific Premature Mortality Due to Ischemic Heart Disease 1985 Heart disease is the leading cause of death in the United States and the third leading cause of years of potential life lost before the age of 65. Ischemic heart disease (IHD)* accounts for 71% of all deaths due to heart disease and 27% of all mortality (1). Data from the National Center for Health Statistics' mortality public-use data tapes for 1985 were used to analyze the incidence of premature mortality due to IHD. *International Classification of Diseases, 9th Revision, codes 410-414. Premature Mortality - Continued Deaths from IHD were stratified by gender for each of the 50 states and the District of Columbia. Age-adjusted IHD death rates for all ages combined were computed from state population estimates for 1984, the latest year for which age- and gender-specific estimates are available (2). In addition, rates of premature mortality due to IHD per 100,000 persons aged 35-64 were computed for each gender and state (Table 1, see page 320). To facilitate interpretation, the states were grouped relative to the national rate (<90%, 90%-110%, and >110% of the national rate). Age-adjusted IHD death rates for 1985 show similar geographic patterns for both men and women. States experiencing age-adjusted rates more than 10% above the national mean were located in the Northeast and Midwest. States with age-adjusted rates at least 10% below the national mean were around Chesapeake Bay; in the Rocky Mountain, Northwest, and Southwest regions of the country; and in Alaska and Hawaii. TABLE II. Notifiable diseases of low frequency, United States *Because AIDS cases are not received weekly from all reporting areas, comparison of weekly figures may be misleading. *Three of the 149 reported cases for this week were imported from a foreign country or can be directly traceable to a known internationally imported case within two generations. |