Leprosy epidemiology and demographics
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]
Overview
Current prevalence rate of leprosy per 100,000 is 3.7. The disease is more prevalent in endemic areas, which represent a potential source of spread of the disease to the rest of the world.
Epidemiology and Demographics
In 1990, the WHO defined a goal of eliminating leprosy as a public health issue within 10 years. Between the years of 1985 and 2010, the number of registered cases of leprosy fell from 5.4 million to 244,796, with prevalence rate per 100,000 falling from 211 to 3.7. However this prevalence is very variable according to the region, since most reported cases come from developing countries, such as India, Brazil and Indonesia. Efforts have been made to decrease the number of cases in endemic areas and to avoid transmission of the disease to other parts of the world, since international travel represents an important vehicle of the bacteria into other parts of the globe. This transmission has such impact that among the cases reported annually in the United States, 75% occur in emigrants.
Incidence
Due to the long incubation period, delay in diagnosis, and lack of laboratory infrastructures it is difficult to measure the true incidence of leprosy.
Two to three million people are estimated to be permanently disabled due to leprosy. India has the greatest number of cases, followed by Brazil and Myanmar.
In 1999, the world incidence of leprosy was estimated to be 640,000; in 2000, 738,284 cases were identified. In 1999, 108 cases occurred in the United States. In 2000, the World Health Organization (WHO) listed 91 countries in which leprosy was endemic.
According to the WHO, the number of new cases has decreased by approximately 107,000 cases (or 21%) from 2003 to 2004. This decreasing trend has been consistent for the past three years.
Prevalence
Registered prevalence reflects the number of active leprosy cases diagnosed with the disease and retrieving treatment with multi-drug therapy (MDT) at a given point in time. In fact, the global registered prevalence of leprosy was 286,063 cases; 407,791 new cases were detected during 2004.
As reported to the WHO by 115 countries and territories in 2006 the global registered prevalence of leprosy at the beginning of 2006 was 219,826 cases. [1] New case detection during the previous year (2005) was 296,499. The annual detection was higher than the prevalence at the end of the year because a proportion of new cases completed their treatment within that year and therefore were removed from the registers. The global detection of new cases continues to show a sharp decline, falling by 110,000 cases (27%) during 2005 compared with the previous year.
The prevalence of Leprosy in the United States is believed to be rising and underreported. There are a rising number of cases worldwide, though pockets of high prevalence continue in certain areas such as Brazil, South Asia (India, Nepal), some parts of Africa (Tanzania, Madagascar, Mozambique) and the western Pacific.
| Table 1: Prevalence at beginning of 2006, and trends in new case detection 2001-2005, excluding Europe | ||||||
| Region | Registered Prevalence
(rate/10,000 pop.) |
New Case Detection during the year | ||||
|---|---|---|---|---|---|---|
| Start of 2006 | 2001 | 2002 | 2003 | 2004 | 2005 | |
| Africa | 40,830 (0.56) | 39,612 | 48,248 | 47,006 | 46,918 | 42,814 |
| Americas | 32,904 (0.39) | 42,830 | 39,939 | 52,435 | 52,662 | 41,780 |
| South-East Asia | 133,422 (0.81) | 668,658 | 520,632 | 405,147 | 298,603 | 201,635 |
| Eastern Mediterranean | 4,024 (0.09) | 4,758 | 4,665 | 3,940 | 3,392 | 3,133 |
| Western Pacific | 8,646 (0.05) | 7,404 | 7,154 | 6,190 | 6,216 | 7,137 |
| Totals | 219,826 | 763,262 | 620,638 | 514,718 | 407,791 | 296,499 |
Table 1 shows that global annual detection has been declining since 2001. The African region reported an 8.7% decline in the number of new cases compared with 2004. The comparable figure for the Americas was 20.1%, for South-East Asia 32% and for the Eastern Mediterranean it was 7.6%. The Western Pacific area, however, showed a 14.8% increase during the same period.
| Table 2: Prevalence and Detection, countries still to reach elimination | ||||||
| Countries | Registered Prevalence
(rate/10,000 pop.) |
New Case Detection
(rate/100,000 pop.) | ||||
|---|---|---|---|---|---|---|
| Start of 2004 | Start of 2005 | Start of 2006 | During 2003 | During 2004 | During 2005 | |
| Brazil | 79,908 (4.6) | 30,693 (1.7) | 27,313 (1.5) | 49,206 (28.6) | 49,384 (26.9) | 38,410 (20.6) |
| Democratic Republic of the Congo | 6,891 (1.3) | 10,530 (1.9) | 9,785 (1.7) | 7,165 (13.5) | 11,781 (21,1) | 10,737 (18.7) |
| Madagascar | 5,514 (3.4) | 4,610 (2.5) | 2,094 (1.1) | 5,104 (31.1) | 3,710 (20.5) | 2,709 (14.6) |
| Mozambique | 6,810 (3.4) | 4,692 (2.4) | 4,889 (2.5) | 5,907 (29.4) | 4,266 (22.0) | 5,371 (27.1) |
| Nepal | 7,549 (3.1) | 4,699 (1.8) | 4,921 (1.8) | 8,046 (32.9) | 6,958 (26.2) | 6,150 (22.7) |
| Tanzania | 5,420 (1.6) | 4,777 (1.3) | 4,190 (1.1) | 5,279 (15.4) | 5,190 (13.8) | 4,237 (11.1) |
| Totals | 112,092 | 60,001 | 53,192 | 80,707 | 81,289 | 67,614 |
Table 2 shows the leprosy situation in the six major countries which have yet to achieve the goal of elimination at the national level. It should be noted that: a) Elimination is defined as a prevalence of less than 1 case per 10,000 population; b) Madagascar reached elimination at the national level in September 2006; and c) Nepal detection reported from mid-November 2004 to mid-November 2005.
Due to the rising numbers, several support groups exist, the headquarters of which is currently in Lynbrook, NY and headed by Brian Marasco, leprosy survivor.
Endemic countries also report the number of new cases with established disabilities at the time of detection, as an indicator of the backlog prevalence. However, determination of the time of onset of the disease is generally unreliable, is very labour-intensive and is seldom done in recording these statistics.
Elimination of Leprosy as a Public Health Problem
In 1991 WHO's governing body, the World Health Assembly (WHA) passed a resolution to eliminate leprosy by the year 2000. Elimination of leprosy is defined as a prevalence rate of less than 1 case per 10 000 persons. The target was achieved on time and the widespread use of multi drug therapy reduced the disease burden dramatically.
- Over the past 20 years, more than 14 million leprosy patients have been cured, about 4 million since 2000.
- The prevalence rate of the disease has dropped by 90% – from 21.1 per 10 000 inhabitants to less than 1 per 10 000 inhabitants in 2000.
- Dramatic decrease in the global disease burden: from 5.2 million in 1985 to 805 000 in 1995 to 753 000 at the end of 1999 to 181 941 cases at the end of 2011.
- Leprosy has been eliminated from 119 countries out of 122 countries where the disease was considered as a public health problem in 1985.
- So far, there has been no resistance to antileprosy treatment when used as multi drug therapy.
- Efforts currently focus on eliminating leprosy at a national level in the remaining endemic countries and at a sub-national level from the others.
References
- ↑ "Global leprosy situation, 2006" (PDF). Weekly Epidemiological Record. 81 (32): 309&ndash, 16. 2006.