Texas, Hawaii, Louisiana, and California.7. An increase in imported cases starting in .... panic White, 17.6% were Asianor Pacific. Islander, and 5.3% were non- ...
Imported Leprosy in the United States, 1978 through 1988: An Epidemic without Secondary Transmission
.............................
III 1,111-M-71
Nrmw..
Timothy D. Mastro, MD, Stephen C. Redd, MD, and Robert F. Breiman, MD
Introduction Leprosy (Hansen disease) is a major health problem in many regions of the world, affecting more than 11 million persons in the 93 countries where it remains endemic.",2 The burden of leprosy is greatest in South and Southeast Asia, Africa, and Latin America.3 This chronic, debilitating, infectious bacterial disease, caused by Mycobactenum leprae, has historically been associated with social stigmatization; before the advent of modern chemotherapy, leprosy patients were traditionally sequestered.4 In northern Europe, Hawaii, Japan, and the continental United States, the incidence of leprosy had declined well before the introduction of effective chemotherapy in the mid-20th century.",5 In the United States, although cases of leprosy continue to be reported, approximately 90% of these cases involve persons entering the country from endemic areas and are defined as imported.6'7 Leprosy has remained endemic in the United States in Texas, Hawaii, Louisiana, and California.7 An increase in imported cases starting in 1978 was identified by review of Centers for Disease Control (CDC) surveillance data from 1971 through 1981.7 We analyzed CDC surveillance data through 1988 to determine whether this trend continued and to characterize the contributing cases. Previously reported cases from 1971 through 1981 were included in the analysis to allow for the evaluation of trends over nearly two decades.7,8
Methods Cases of leprosy are reported to CDC by state and territorial health departments using a standardized report form. Diagnosis is determined by clinical and laboratory (biopsy and/or skin smear) evalua-
tion; type of leprosy is reported as lepromatous, dimorphous/borderline, tuberculoid, or indeterminate. The report includes patient's date of birth, date of entry into the United States, date of onset of symptoms of leprosy, date leprosy was first diagnosed by a physician, and date of report. Cases are categorized as indigenous or imported. Indigenous cases are defined as illness in persons born in the United States who have neither lived nor been stationed for military service outside the country. Imported cases are defined as illness in persons bom outside the United States with onset either before or after entering the country, or illness in persons bom in the United States who traveled outside the country and may have acquired infection in leprosy-endemic areas. Reports were excluded from the analysis if missing data prevented categorization as imported or indigenous. Cases were recorded by the year of report, which often differed from the year of onset. Data on immigrant and refugee populations entering the United States were obtained from the US Immigration and Naturalization Service and the Department of State, Bureau for Refugee Programs, respectively. Asian countries were divided into three regions: (1) Southeast Asia-Cambodia, Indonesia, Laos, Malaysia, Myanmar (Burma), Philippines, Singapore, Thailand, and Vietnam; (2) East Asia-China, Hong Kong, Japan, Korea, and Taiwan; and (3) South and The authors are with the Respiratory Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control, Atlanta, Ga. Requests for reprints should be sent to Timothy D. Mastro, MD, Mailstop C-09, Centers for Disease Control, Atlanta, GA 30333. This paper was submitted to the Journal September 30, 1991, and accepted with revisions December 31, 1991.
American Journal of Public Health 1127
Mro et aL
350
300 250 (A
Q) U)
200
C
U
150 x importeaJ spectea
100 -
50 _ 50 71
72 73 74 75
76 77 78 79 80 81
82 83 84 85 86 87 88
Year s prosycas In the Unit Sas reported fm 1971 through 1988, and expd and excess Imported cases from 1978 through 1988.
FiGURE -mportedad dig
West Asia-Afghanistan, Bangladesh, India, Lebanon, Pakistan, Saudi Arabia, Sri Lanka, and Yemen. The expected annual number of imported cases for each region of the world was calculated using the number of cases reported from 1971 through 1977 as a baseline. Excess cases reported from 1978 through 1988 are defined as the number of cases observed minus the number of expected cases.
Remt Cases From 1971 through 1988, 3554 cases of leprosy were reported in the United States. Reports of 3420 (96.2%) cases contained sufficient information to be included in the analysis; 3101 (90.7%) were imported, while 319 (9.3%) were indigenous. Of the imported cases, 2973 (95.9%) involved persons born outside the United States. The number of indigenous cases was roughly stable throughout the period, with a mean of 17.7 (range = 10 to 29) reported per year. The number of imported cases reported annually was relatively constant from 1971 through 1977 (mean = 119, range = 88 to 136), increased to 307 cases in 1985, and decreased to 102 cases in 1988 (Figure 1).
Impored Cases Reports of imported cases were received from 47 states, Puerto Rico, and the District of Columbia. Six states re1128 American Journal of Public Health
ported 2468 (79.6%) of these cases: California (1306; 42.1%), Hawaii (481; 15.5%), Texas (255; 8.2%), New York (197; 6.4%), Washington (115; 3.7%), and Illinois (114; 3.7%). The mean (± SD) age of persons with leprosy was 38 (±17) years; 63.2% were male. The type of leprosywas multibacillary (lepromatous or borderline) in 67.8% of cases, 28.4% of cases were tuberculoid, and 3.8% were indeterminate. Persons born in Southeast Asia accounted for 47.8% of all imported cases; however, using 1971 through 1977 as the baseline period to calculate the expected numbers of cases, persons from this region accounted for 73.4% of the excess cases reported from 1978 through 1988 (Table 1). Among cases from Southeast Asia, 743 (50.2%) involved persons from the Philippines and 673 (45.4%) involved persons from the three Indochinese countries of Vietnam (388 cases), Cambodia (215 cases), and Laos (70 cases). However, because of the small number of cases among Indochinese (71 cases) reported from 1971 through 1977, 69.8% of the excess cases from Southeast Asia and 51.3% of all excess cases involved persons from Indochina. The increase in cases of leprosy imported from Indochina followed an increase in refugees from this area entering the United States (Figure 2). The first large group of refugees arrived in 1975, primarily from Vietnam,9 followed by large groups in 1979 to 1982 consisting of refugees from Vietnam, Cambodia, and Laos.
Of the excess cases reported from 1978 through 1988, 203 (21.2%) involved persons from the Philippines. The mean annual number of Filipino immigrants to the United States from 1978 through 1988 was 45 025, compared with 34 505 from 1971 through 1977, an increase of 30.5%; the mean annual number of leprosy cases increased 61.7% from 30.0 to 48.5. Analysis of 1-year cohorts of persons who entered the United States from 1971 through 1988 and who had onset of leprosy after immigration indicates that the highest rates of onset occurred within 12 months of arrival, with a sharp drop in onset during succeeding years of residency. For Filipino immits, the rate in the first year was 30.9 per 100 000 immigrants, compared with 16.8 per 100 000 refugees among Indochinese and 4.7 per 100 000 among all other immigants. Persons from Indochina with leprosy were younger (mean age = 33 years) than persons from the Philippines (mean age = 43years;P < .001)andotherareas (mean age = 38 years; P < .001). Onset of leprosy occurred after entry into the United States in only 53.9% of cases from Indochina, compared with 82.4% of cases from the Philippines (P < .001) and 78.5% of cases from all other areas (P < .001). Also, the mean delay from onset of illness to time of diagnosis was shorter for cases from Indochina (6 months) than for cases from the Philippines (10 months; P < .001) and cases from all other countries (11 months; P < .001). Leprosy was less commonly multibacillary (lepromatous or borderline) in persons from Indochina (50.8%) and the Philippines (64.5%) than in persons from other countries (77.0%; P < .001).
Indgenous Cases Reports of indigenous cases were received from 17 states; the 4 states where leprosy is endemic reported 298 (93.4%) of these cases: Texas (191; 59.9%), Hawaii (58; 18.2%), Louisiana (40; 12.5%), and California (9; 2.8%). Of the remaining 21 indigenous cases, 10 involved persons who had resided in 1 of these 4 states. The likely place of exposure for the remaining 11 cases could not be determined from reported information. During the 18-year surveillance period, no state had a significant increase or decrease in the number of indigenous cases. The mean (± SD) age of personswith indigenous cases of leprosy was 49 (±19) years; 53.9% were male. Race/ethnicity was reported as Hispanic for 39.5% of persons with leprosy, 35.7% were non-HisAugust 1992, Vol. 82, No. 8
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panic White, 17.6% were Asian or Pacific Islander, and 5.3% were non-Hispanic Black (race/ethnicity was not reported for 2.8%). One hundred ninety-six (61.4%) cases were classified as lepromatous or borderline leprosy, 93 (29.2%) were tuberculoid, and 28 (8.8%) were indeterninate. The mean delay from onset of illness to diagnosis of leprosy was 10 months.
iscwusion An epidemic of imported leprosy in the United States began in 1978 and ended by 1988. The increase was primarily due to cases that occurred among the large groups of refugees that entered the United States in 1975 and 1979 through 1982 from the Indochinese countries of Vietnam, Cambodia, and Laos. The number of cases reported annually among this group decreased after the number of refugees stabilized following 1982. Imported cases of leprosy appear to present a negligible riskfor transmission in the United States; no coincident increase in indigenous leprosy occurred during this time. However, since leprosy has an incubation period of several years and since most household contacts of immigrants and refugees are likely to be immigants and refugees themselves, it is possible that cases resulting from transmission in the United States would have been categorized as imported cases. For all groups with imported disease, the highest rate of onset of leprosy occurred in the first year after entry into the United States, and a sharp drop was observed by the second year. Although the prevalence of leprosy in the Philippines was estimated to be 1 to 1.9 cases per 1000 population compared with 5 to 9.9 cases per 1000 population in Indochina,' higher rates were observed among immigrants from the Philippines than among refugees from Indochina. The increase in imported cases from the Philippines (21.2% of ex-
cesscases)wasonlypartiallyexplainedby an increase in immigrants and may have been due, in part, to improved case reporting. However, only 17.6% of cases of leprosy among Filipinos were detected prior to entry to the United States compared with 46.1% of cases among Indochinese, perhaps reflecting a more efficient screening procedure for refugees. Also, methods of counting refugees and immigrants are different, and comparisons of rates of leprosy between these two populations should be made with caution. Refugees are eligible for special processing related to admission to the United
August 1992, Vol. 82, No. 8
200
100
-Cases
u
f't.0
40 ~~ ~
~
~
~
~
~
~
~
~~ 5
CL
so
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J
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71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88
Year prosy ca among Indochinese es and number of refugees who entered the United States from 1971 through 1988.
FIGURE 2-Report
States. A refugee's date of admission is recorded by the Immigration and Naturalization Service as the date of entry into the United States as a refugee; few enter uncounted.10 This is in contrast to immigrants, who are recorded by the year they adjust to permanent resident status, not the year they enter the countly. Not reflected in immigrant figures are persons in the United States awaiting adjustment of status and those in the country temporarily and illegally. No rate was calculated for Mexican immigrants because of an inability to accurately estimate the number of Mexicans in the United States at risk for leprosy. Although refugees and immigrants who entered the United States from 1971 through 1988 were screened for leprosy, the majority of imported cases had onset
of illness after entering the United States, with the highest rate of onset in the year following ently. Given the slow progression of clinical signs and symptoms,4'5 it is likely that many of these persons had clinical evidence of leprosy that was not detected at the time of entry. Although most (67.8%) imported cases were lepromatous or borderline and therefore were potentially infectious, there is no evidence that imported cases of leprosy resulted in transmission in the United States. This apparent lack of transmission may be due, in part, to a combination of better housing conditions, resulting in decreased crowding, and improved nutritional status in the United States. Leprosy transmission is believed to result from prolonged and intimate contact with a person with multibacillary (lepromatous or borderline) dis-
American Journal of Public Health 1129
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ease; malnutrition is widely considered to predispose to leprosy.5 In the United Kingdom, despite the diagnosis of more than 1250 cases of imported leprosy since 1951, there have been no reports of secondary cases." A recent investigation of a case of imported active lepromatous leprosy in an elderly man in an English nursing home detected no secondary cases of leprosy, but immunologic studies suggested that M. leprae may have been transmitted (leading to subclinical infection) to 2 of 66 persons with whom the index case had daily contact.1" The data presented here provide additional evidence that persons with imported leprosy, including lepromatous forms, do not pose an appreciable infectious risk in the United States. Furthermore, current chemotherapy, which should be initiated promptly following diagnosis, is highly effective for all forms of leprosy; infectiousness is generally lost within 3 days of treatment with a multidrug regimen including rifampin.3.2 Leprosy, active tuberculosis, human immunodeficiency virus infection, and five bacterial sexually transmitted diseases were classified in the Immigration and Nationality Act as "dangerous contagious diseases" for which aliens may be excluded from admission to the United States.13,14 This study supports the proposed change to this act that would remove leprosy from the newly named list of "communicable disease of public health significance."'13,14 Continued classification of leprosy as an excludable condition unjustifiably furthers the social stigmnatization historially associated with this di-
agnosis. The World Health Organization has recently set as a goal the worldwide elimination of leprosy as a public health threat;
elimination was defined as the reduction ofprevalence tobelowone case per 10 000 population.2 In the United States, continued surveillance for leprosy will be necessary to monitor changes in the distribution of indigenous cases, in particular, to further document the decrease in cases in Hawaii15 and to determine whether the small number of reported cases in California truly represents endemic disease. Surveillance is also important to monitor trends in imported disease and to determine whether household contacts, notably children, of immigrants and refugees are at increased risk for leprosy. Clicians should be familiar with the clinical manifestations of leprosy and considerthe diagnosis, particuarly for persons from leprosy-endemic areas, both in the United States and abroad. All household contacts ofpersons with leprosy should be thoroughly eValuated for diseas.'6 Even if indigenous leprosy is eliminated in the United States, immignts and refugees entering the country from leqprsy-endemic areas are likely to continue to present with new cases of disease. [l
Acknowledgments Portions of this paper were presented at the 30th Interscience Conference on Antimicrobial Agents and Chemotherapy, Atlanta, Ga, October 1990. We thank Sheila F. Collin for her efforts in maintaining the leprosy surveillance system and Drs. Robert C. Hasting and Robert C. Good for valuable suggestions for the manu-
script.
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Organization;
1985. WHO Technical Report Series 716.
2. World Health OWnization. UNDP/World Bank/WHO Special Prgrane for Researc and TiidWg in Tropcal Diseases (TDR). Geneva: World Health Organization; 1991. TDR news, no. 36. 3. Noordeen SK Leprosy control through multidrug therapy (MDT). Bull WHO. 1991;69:263-269. 4. Meyers WM. Leprosy. In: Strickland GT, ed. Hunter's Tropical Medicine. Philadelphia, Pa: WB Saunders; 1991:483-494. 5. Fine P. Leprosy: the epidemiology of a slow bacterium. Epidemiol Rev. 1982;4: 161-188. 6. EnnaCD, Jackson RR, Trautman JR, Sturdivant M. Leprosy in the United States, 1967-76. Public Health Rep. 1978;93:468473. 7. Neil MA, Hightower AW, Broome CV. Leprosy in the United States 1971-1981. J Infect Dis. 1985;152:1064-1069. 8. Golden GS, McCormick JB, Fraser DW. Leprosy in the United States, 1971-1973.J Infect Dis. 1977;135:120-125. 9. Centers for Disease Control. Hansen's disease in Vietnamese refugees. MMWR 1976;24:455-456. 10. US Imigration and Naturalization Service. Statcal Yearbook of the Immigation and Naturalization Service, 1988. Washington, DC: US Government Printing Office; 1989. 11. Dockrell HM, Eastcott H, Young S, MacFarlane A, Hussain R, Waters MEFR. Possible t ssion of Mycobateiiwn leprae in a group of UK leprosy contacts. Lancet. 1991;338:739-743. 12. Anonymous. Leprosy (Hansen's diseas). In: Benenson AS, ed. Conthl of CommunicableDiseasesinMan. Washington, DC: American PublicHealth Association; 1990: 243-247. 13. Medical examination of aliens. Federal Register. January 23, 1991;56:2484. 14. Medical examination of aliens. Federal Register. May 31, 1991;56:25000. 15. Worth RM, gaars MR. Immigation and leprosy in Hawaii, 1960-1981. Int J
Lepr. 1982;50:335-341. 16. Filice GA, Fraser DW. Management of household contacts of leprosy patients. Ann Inten Med. 1978;88:538-542.
