Globally, the number of new leprosy cases has decreased modestly in the past few years1; the latest report from the World Health Organization (WHO) stated that the leprosy incidence in 2017 was down by 7.8% from that in 2010.2 The WHO target also changed in that report from the “elimination of leprosy as a public health problem” to “a reduction of the disease burden due to leprosy.” The WHO global leprosy strategy for 2016–2020 calls for “accelerating towards a leprosy-free world” and was adopted by most countries.
The leprosy prevalence in China is currently at a low epidemic level but has an uneven distribution. In 2013, China reported 924 newly detected cases of leprosy; this was the first time that the annual number of newly detected leprosy cases was under 1,000, and this number has continued decreasing. From 2010 to 2017, the rate of decline in newly detected leprosy cases in China was 52.1%, which is higher than the world average level. The leprosy incidence in China has accordingly decreased in recent years.3–5 Here, we describe the epidemiological characteristics of leprosy incidence in 2017, which will provide the measures basis to the China leprosy control program.
Materials and methods
All data used in this study were collected from Annual Leprosy Report Forms, which were submitted by all the provinces of China excluding Hong Kong, Macao, and Taiwan.
Annual Leprosy Report Forms are part of the statistical report forms in Leprosy Management Information System in China (LEPMIS), which is maintained by National Center for Leprosy Control, China CDC. All the data are first collected by data reporters from leprosy patient records, which are reported by workers, who manage leprosy patients directly at county, prefecture, or provincial level. The leprosy data managers at provincial level are responsible for data quality control via LEPMIS or/and patient visits. When the data are finally confirmed, the system issues the report forms automatically.
We used WPS office 2016 (Kingsoft Corporation, China) and EpiCalc 2000 (designed by Joseph Gilman and Mark Myatt, UK) for data compilation and statistical analysis. Qualitative data were described as percentages and analyzed using chi-square (χ2) tests as indicated. The reported P-values are two-sided, and P-values of less than 0.05 were considered to be statistically significant.
Newly detected cases
A total of 634 newly detected leprosy cases were reported nationwide in 2017. Compared with the 672 cases reported in 2016, this indicates a decrease of 38 leprosy cases (5.6%); furthermore, this is a reduction of 52.1% compared with the 1,324 reported cases of leprosy in 2010. The average annual decrease in newly detected leprosy cases from 2010 to 2017 was 10%.6
By the end of 2017, a total of 2,697 leprosy cases defined as not reaching clinical cure based on the national guidelines for the diagnosis for leprosy were registered nationwide. This indicates a decrease of 228 cases (7.8%) compared with the 2,925 uncured leprosy cases in 2016; furthermore, this is a reduction of 3,335 cases (55.3%) compared with the 6,032 cases of uncured leprosy reported in 2010. The average annual decrease in the number of registered leprosy cases from 2010 to 2017 was 10.9%.
Except for a slight increase in 2012, the number of newly detected cases and reported incidence of leprosy in China from 2010 to 2017 has shown declines (Fig. 1).7 The number of newly detected cases decreased from 1,324 in 2010 to 634 in 2017, with an average annual decline of 10%, and the detection rate dropped from 0.099/100,000 in 2010 to 0.046/100,000 in 2017, with an average annual decrease of 10.4%.
In 2017, 23 of 31 provinces, autonomous regions, or municipalities reported newly detected cases of leprosy, whereas 8 (ie, Tianjin, Shanxi, Jilin, Heilongjiang, Shanghai, Inner Mongolia, Liaoning, and Ningxia) did not report any new cases (Fig. 2). Yunnan province reported the largest number of newly detected leprosy cases (159 cases), followed by Sichuan (96 cases), Guizhou (81 cases), and Guangdong (74 cases). These four endemic provinces accounted for 64.7% of China's newly detected leprosy cases. Additionally, Yunnan province had the highest reported incidence rate of leprosy in 2017 (0.333/100,000), followed by Tibet (0.237/100,000), Guizhou (0.226/100,000), Sichuan (0.116/100,000), and Guangdong (0.066/100,000).
Among the newly detected cases of leprosy in 2017, 417 patients were male (65.8%) and 217 patients were female (34.2%), yielding a male-to-female ratio of 1.9:1. Newly detected cases of leprosy were reported in all age groups across the country. The average age at diagnosis was 43.9 years. The overall age range spanned from 9 to 84 years, among which the highest number of newly detected cases occurred in the 40–49 years age group, followed by the 30–39 years age group.
According to the WHO definition of disability, there were 127 newly detected leprosy cases in China with grade 2 disability (G2D),8 accounting for 20% of the newly detected cases in 2017. The proportion of G2D cases among the subset of newly detected cases has fluctuated between 18.6% and 28.7% from 2010 to 2017. This indicates a decrease of 21 cases (14.2%) compared with the 148 newly detected leprosy cases with G2D in 2016; furthermore, this is a reduction of 171 cases (57.4%) compared with the 298 newly detected leprosy cases with G2D in 2010. However, in the past eight years, the proportion of G2D cases in China among the newly detected leprosy cases was the highest among all countries in the Western Pacific, and it has usually been higher than the world average level.2
Based on the WHO definition for leprosy classification, there were 582 multibacillary (MB) leprosy cases and 52 paucibacillary leprosy cases among the newly detected cases of leprosy, respectively accounting for 91.8% and 8.2%. The proportion of MB cases among the newly detected cases has fluctuated between 80.8% and 91.8% from 2010 to 2017.
In 2017, a total of 52 relapsed cases of leprosy were registered nationwide; this indicates an increase of 6 cases (13.0%) compared with the 46 relapsed cases in 2016, but a reduction by 44 cases (45.8%) compared with 96 relapsed cases reported in 2010. Among the 52 relapsed cases, there were 28 cases of relapse (53.8%) that were detected after the administration of multidrug therapy (MDT). The other 24 relapsed cases (46.2%) occurred after dapsone (DDS) monotherapy. The proportion of relapsed cases after MDT has fluctuated between 36.1% and 56.9% from 2010 to 2017 with no significant change (χ2 = 12.96, P > 0.05).
There were 2,697 registered cases of leprosy in China by the end of 2017, yielding a prevalence rate of 0.194/100,000. This is a decrease of 228 cases (7.8%) compared with the 2,925 registered leprosy cases in 2016 and a decrease of 3,335 cases (55.3%) compared with the 6,032 registered cases in 2010. The leprosy prevalence rate decreased from 0.450/100,000 in 2010 to 0.194/100,000 in 2017, which is a reduction of 56.9%. The average annual decrease in the leprosy prevalence rate was 11.3%.
In 2017, Yunnan province reported the largest number of leprosy cases (538), accounting for 19.9% of all registered cases in China, followed by Sichuan (404), Guangdong (273), Guizhou (261), and Hunan (167) provinces. Yunnan province also had the highest prevalence rate of leprosy (1.128/100,000), followed by Tibet (1.127/100,000), Guizhou (0.729/100,000), Sichuan (0.487/100,000), and Hainan (0.324/100,000).
The elimination of leprosy in China has been defined as a reduction of the disease prevalence to <1 case per 100,000 individuals in China.
At the provincial level, only Yunnan and Tibet had not reached this target as of 2017. A total of 89 counties, not including those with a population of < 300,000 and no more than three registered active cases of leprosy, did not reach the elimination target at the county level in 2017; this is a decrease of 24 counties compared with the 113 counties that did not meet this target in 2016. Yunnan had the highest number of counties (37 counties) that did not meet the elimination target, followed by Sichuan (18 counties) and Hunan (9 counties). These three provinces accounted for 71.1% of China's non-target-reaching counties. In these areas, two counties had leprosy prevalence rates above 1 case per 10,000 individuals.
China has not been categorized by the WHO as a highly endemic country for leprosy since 2013.9 However, the number of newly detected cases of leprosy in China is still ranked within the top 15 in the world and is the second highest in the Western Pacific Region, just behind the Philippines.1 The prevention and control for leprosy is still a big challenge.
Overall, the leprosy epidemic situation in China is low, but the distribution of newly detected leprosy cases is unbalanced. In 2017, 57.1% of leprosy patients were detected in the southwest of China, in areas such as Chongqing, Sichuan, Guizhou, Yunnan, and Tibet, especially in places with poor general living environments, poor transportation systems, and undeveloped economies.10 Meanwhile, because of movement within the Chinese population, increasing patients, who then received MDT treatment in the east coast regions and developed provinces, such as Beijing, Guangdong,11 and Zhejiang, have been diagnosed with leprosy in the southwest of China. To stop the further spread of leprosy, it is important to focus on both the high incidence areas and the areas with high migrant populations.12-13
One of the principal targets in the global leprosy strategy for 2016–2020 is an absence of leprosy cases with G2D in children.2 In 2017, there were nine cases of leprosy diagnosed in children in China, none of whom had any visible deformity or disability. However, the proportion of children among the newly detected leprosy cases has fluctuated between 1.5% and 2.9% over the past eight years, which means that the screening for close contacts of leprosy patients needs to be strengthened.14-15 The male-to-female ratio for leprosy cases in China for 2017 was 1.9:1; this ratio is not statistically different compared with the male-to-female ratios in China from the past eight years. However, the male-to-female ratio of leprosy cases in China is different from those in other countries may be due to the differences in the sex ratio and accessibility of health service between China and other countries.16–18
The numbers of newly detected cases and MB cases in China have continuously decreased, but the ratio of MB among the newly detected leprosy cases has fluctuated between 80.8% and 91.8%, with slight increases. Additionally, the cases of lepromatous leprosy and borderline lepromatous leprosy accounted for 63.6% of the total leprosy cases in 2017, which shows that most of the newly detected cases in China were highly infectious and that the transmission of leprosy may still be a serious problem in the community.
One of the most serious problems associated with leprosy in China is the high level of G2D cases that have been reported over the past few years. Because leprosy is a rare disease in China, more advanced techniques are needed to improve the early diagnosis of leprosy19; furthermore, the training for dermatologists and primary healthcare workers must be strengthened to reduce the leprosy burden due to G2D.20 Cases of relapsed leprosy, especially after MDT treatment, should be monitored for a long time.21 These cases must also be distinguished from cases of reinfection of leprosy22 and leprosy reaction.
In conclusion, our analysis of the available leprosy data for China in 2017 revealed that, compared with the historical data from 2010 to 2016, the epidemic level of leprosy in China is low with a markedly uneven geographically distribution. These findings may guide the design of precise control measures to enhance the prevention and control of leprosy in China.
This article was supported by CAMS Innovation Fund for Medical Sciences (CIFMS-2017-I2M-1–017), Innovation research on critical diseases (2016ZX320014) and The Netherlands Leprosy Relief (ILEPNR 412.90.01). We thank the staff and data reporters at local leprosy control department of all levels of CDCs and other organizations responsible for leprosy control for their assistance with the epidemiological data collection and reporting.
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