Abstarct
Background
Hainan Province, the only tropical province in China, remains a high-burden area for tuberculosis (TB). However, up-to-date data on the prevalence and demographic disparities of TB cases are lacking. To address these gaps, we conducted a population-based TB prevalence survey.
Methods
We conducted a population-based, cross-sectional survey using a multistage stratified random cluster sampling design. The study included adults (aged ≥15 years) who had resided in their households for at least six months in Hainan. Screening and diagnostic procedures followed World Health Organization (WHO) guidelines. We calculated the crude prevalence of active PTB among participants with valid results and applied inverse probability weighting combined with multiple imputation to account for missing data. Prevalence estimates were compared by rural–urban residence, age group, sex, and ethnicity.
Findings
In 2023, a total of 67,681 individuals were enumerated, of whom 35,219 (52.0%) were eligible for the survey. Among them, 33,778 (95.9%) participated. We identified 144 cases of active PTB, including 21 smear-positive and 36 bacteriologically confirmed cases. The weighted prevalence of active PTB was 355 (95% CI 291–418) per 100,000 population. The prevalence of smear-positive PTB was 63 (95% CI 36–90) per 100,000, and bacteriologically confirmed PTB was 96 (95% CI 63–129) per 100,000. Of the 144 active PTB cases, 120 (83.3%) were male, 62 (43.1%) were aged 60 or above, and 55 (38.2%) were re-treated cases. Notably, 85 (59.0%) of all active PTB cases and 17 (47.2%) of bacteriologically confirmed cases reported no TB-related symptoms. Both proportions are substantially higher than those reported in the 2010 national survey (43.1% and 14.2%, respectively).
Conclusions
Although the prevalence of active PTB in Hainan has declined significantly since 2010, it remains higher than in other parts of China. Marked disparities were observed by sex, age, geographic region, and ethnicity. Particular attention should be directed toward men aged 45 years and above, the Li ethnic group, and rural populations. The high proportion of re-treated cases and asymptomatic patients underscores the need to enhance treatment quality and strengthen active case-finding strategies to accelerate TB elimination efforts in Hainan Province.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12879-026-13531-z.
Keywords: Tuberculosis, Hainan Province, Prevalence, Asymptomatic
Introduction
Tuberculosis (TB) remains one of the significant public health issues worldwide, particularly in low-income and middle-income countries. According to the report of World Health Organization (WHO), of the estimated 10.6 million people who fell ill with TB globally in 2022, India accounted for 27% and China accounted for 7.1% [1]. Although substantial progress in reducing the burden of TB in China has been made, achieving the goal of ending TB remains a challenge; moreover, the burdens imposed by TB have variably persisted in different provinces of China [2, 3]. Therefore, regional surveys are essential to formulate effective regional response to TB.
Hainan is a tropical island in the southernmost part of China and is China’s second largest island [4]. The unique geographical location of Hainan means the climate characteristics are different from those of inland areas in China [5]. As China’s only tropical province, most of the island has a humid tropical monsoon climate characterized by hot and humid summers with mild, pleasant winters [6]. The annual average temperature of Hainan usually ranges from 24 °C to 35 °C in the summer and from 24 °C to 35 °C in the winter [7]. Such a climate could contribute to the proliferation and spread of micro-organisms, so it is one of the provinces known to have a high burden of tuberculosis [8, 9]. From 2013 to 2023, the average annual notification rate of PTB among individuals aged ≥ 15 years in Hainan Province was 62.32 per 100,000 population and the corresponding average annual notification rate of bacteriologically confirmed TB was 21.30 per 100,000 population [10]. Further, Hainan Province had China’s fifth-highest notification rate of PTB cases in 2023. However, the last regional survey in Hainan Province dated back to 2010 [3]. Since the establishment of the Hainan Free Trade Port in 2018, population mobility within and into Hainan Province has increased, posing new challenges for tuberculosis (TB) prevention and control efforts [11]. Hainan Province is also characterized by substantial ethnic diversity. In addition to the Han majority, the Li ethnic group represents the largest ethnic minority in the province and has historically inhabited Hainan for centuries. In this context, updated, population-based data are needed to re-evaluate the overall tuberculosis burden in Hainan Province and to assess differences across population subgroups.
Therefore, the Hainan Center for Disease Control and Prevention (CDC) conducted a population-based pulmonary tuberculosis (PTB) prevalence survey, using a standardized study design and rigorous data quality control, to reassess the burden of PTB in the resident adult population of Hainan Province. In this report, we present a detailed analysis of the prevalence of active PTB and the demographic determinants of active PTB.
Methods
Study design
This population-based, cross-sectional survey aimed to estimate the prevalence of active PTB among adults in Hainan Province. A multistage stratified random cluster sampling design was used. Eligible participants were adults aged ≥ 15 years who had resided in one of the selected cluster areas for at least six months prior to the survey. Ethical approval was granted by the Hainan Center for Disease Control and Prevention.
Cluster selection and sample size calculation
A cluster was defined as a community in a city, town, or village within a township. Counties or districts were first selected with probability proportional to population, ensuring that each had at least one cluster. Communities within counties or districts were then selected by simple random sampling. For Hainan Province, 20 clusters were included in both 1990 and 2010. Given the substantial decline in TB prevalence since 1990, the present survey appropriately increased the number of clusters to 30 to maintain statistical power and representativeness.
Sample size calculations followed WHO guidance for TB prevalence surveys and were aligned with the design of the 2010 national survey to ensure comparability. Based on previous national surveys, the anticipated prevalence of active PTB in Hainan was projected to be 404 per 100,000 population aged ≥ 15 years. To achieve 25% relative precision for smear-positive PTB prevalence, assuming a design effect of 2 and 90% participation, 30 clusters of 1,127 individuals each—totaling 33,810 participants—were required (Table 1). If the population of eligible individuals in a cluster was fewer than 1,127, adjoining communities were included to reach the target size. If the population exceeded the target, families within the cluster were randomly selected until the target cluster size was achieved.
Table 1.
Survey design and methodology
| Sampling design | |
|---|---|
| Item | Description |
| Sampling frame | Hainan Province, China |
| Sampling design | Multistage stratified random cluster sampling with probability proportional to size |
| Strata | Urban/rural |
| Sampling unit |
Urban: community in a city or town Rural: village in a township |
|
Sample size assumptions Estimated prevalence of active PTB Precision Design effect Response rate Sample size (estimated) 100 000 |
404 per 100,000 (≥15 years) 0.25 2.0 0.9 33810 |
| Number of clusters | 30 |
| Cluster size | 1,127 |
| Target sample size | 33,810 individuals |
|
Eligibility criteria Age Residency |
≥15 years Individuals who lived for ≥6 months in the household |
| Screening criteria | |
|
Questionnaire Chest X-ray Other Participants |
Cough, sputum, and hemoptysis for at least the past 2 weeks Any lung abnormality Participants with known active pulmonary TB with normal chest X-ray, and chest X-ray exempted |
| Laboratory methodology | |
|
Smear Culture Xpert® MTB/RIF TB drug susceptibility test |
Three samples: spot, evening, and early morning Ziehl–Neelsen staining Löwenstein–Jensen medium Done Rifampicin resistance detected by GeneXpert MTB/RIF; phenotypic DST on solid media performed for culture-positive isolates |
Procedures
Survey teams composed of trained medical professionals conducted field investigations in each selected county or district. Prior to fieldwork, the teams received standardized training in census taking, symptom screening, chest radiography, sputum sample collection and handling, and electronic data capture. Household lists were obtained from the local registration offices, and a census was performed by visiting all households. Screening sites (such as town halls, community centers or health facilities) were established for participant enrollment and examination.
At screening sites, informed consent was obtained and participants were registered in the electronic survey system (Supplementary file 1). Screening consisted of symptom assessment and chest radiography, except for individuals unable to undergo X-ray (Table 1; Supplementary file 2). Chest radiographs were obtained using digital X-ray systems. Fixed digital units were used at permanent facilities such as county hospitals, whereas mobile radiography vans were deployed at temporary or remote sites. All images were interpreted on-site by qualified radiologists. Any radiograph showing pulmonary abnormalities, including opacities, cavities, fibrosis, pleural effusion, or calcifications, was classified as abnormal. For quality assurance, all abnormal chest radiographs and a random 10% of those initially read as normal were reviewed by a senior radiologist or technical expert for a final decision. If the central review identified an abnormality missed in the field, the participant’s screening result was updated to screen-positive, prompting collection of sputum samples for further testing.
Participants reporting cough, sputum production, or hemoptysis of any duration, those with chest radiographs classified as abnormal after expert review, or those who did not undergo X-ray screening were requested to provide three sputum samples (on the spot, the same evening, and early in the morning on the following day).Samples were transported daily under cold-chain conditions to 18 designated laboratories participating in the survey. The culture media used in this survey were centrally procured by the provincial reference laboratory and distributed to the participating laboratories.
Sputum specimens were examined by Ziehl–Neelsen smear microscopy within 24 hours of collection and by GeneXpert MTB/RIF within seven days. Two samples per participant were selected for culture on Löwenstein–Jensen medium based on smear and GeneXpert results or specimen quality. In addition to GeneXpert MTB/RIF testing for rifampicin resistance, phenotypic drug susceptibility testing of rifampicin using solid media was performed for all culture-positive isolates. Laboratory procedures followed national TB diagnostic standards. The provincial reference laboratory conducted ongoing quality control, including re-reading all AFB-positive smears and 10% of AFB-negative smears. All participants who are positively screened via X-ray of the chest and/or symptom will be referred directly to their local community health center for further medical follow-up and care. New cases of TB diagnosed during the survey will be reported to the National TB Program and the district TB coordinator.
Definitions of PTB cases
Active PTB cases were classified as bacteriologically confirmed or clinically diagnosed. A bacteriologically confirmed PTB case was defined as any screen-positive participant with at least one positive result by smear microscopy, GeneXpert MTB/RIF, or culture for MTB. Clinical diagnosis was based on symptoms, radiographic findings, clinical history, and expert panel review. Participants were classified as new PTB cases if they had no history of prior anti-tuberculosis treatment. Those who had received anti-tuberculosis therapy for at least one month in the past, including individuals with prior treatment completion, treatment failure, or irregular treatment, were defined as retreated PTB cases.
Statistical analysis
Data were recorded using software developed by the Hainan CDC and analyzed in R version 13.0. Missing smear, GeneXpert, and culture results were handled using multiple imputation, with age, sex, ethnicity, TB history, and type of residence included as covariates. Following WHO tuberculosis prevalence survey guidelines [12, 13], two complementary analyses were then conducted. First, a complete-case analysis was performed to estimate the crude prevalence of PTB among participants with valid results. Second, an individual-level analysis combined inverse probability weighting to adjust for differences in participation by age and sex, providing population-representative prevalence estimates. 95% confidence intervals were calculated using the Clopper–Pearson exact method with robust standard errors. Both approaches were applied to estimate overall prevalence and stratified prevalence by rural–urban residence, age group, sex, and ethnicity.
Role of the funding source
The funder of the study had no role in study design, data collection, data analysis, data interpretation, or writing of the report. The Hainan CDC was responsible for the survey design, field investigation, and data collection. The Hainan CDC had full access to all the data in the study and had final responsibility for the decision to submit for publication.
Results
In 2023, 67 681 individuals were counted during the survey. Of these, 35 219 (52.0%) were eligible for survey participation. Of these, 33 778 (95.9%) participated (Fig. 1). Figure 2A illustrates the spatial distribution of all sampling locations, with each site annotated by the number of participants enrolled. The proportions of participants in this survey over 80 and under 40 years old were lower than those of the general population of Hainan (Fig. 2) [14]. Of them, 25 421 (75.3%) were Han, 7736 (22.9%) were Li, and 621 (1.8%) were of other ethnicities. Of them, 8605 (25.5%) were from urban areas, and 25 173 (74.5%) were from rural areas. 1441 (4.1%) eligible individuals did not participate in screening (Table S1). Non-participation was higher in men (811 [4.9%] of 16 453) than in women (627 [3.3%] of 18 763), was slightly higher in rural areas (1121 [4.3%] of 26 294) than in urban areas (320 [3.6%] of 8929).
Fig. 1.
Survey flow: census to final outcomes
Fig. 2.
(A) spatial distribution of sampling locations across the main island of Hainan. Each sampling site is labeled with the number of participants enrolled and categorized as urban or rural. The map illustrates the geographic coverage of the survey and the population distribution across study sites. (B) age and sex distribution of the participating population in our Hainan pulmonary tuberculosis prevalence survey. (C) age and sex distribution of the general population of Hainan
A total of 144 active PTB patients were found in this survey, including 36 bacteriologically confirmed cases. Among the bacteriologically confirmed cases, 21 (58.3%) were smear-positive, and 35 (97.2%) were positive by culture and/or GeneXpert, of whom two were identified as rifampicin-resistant. Among 21 smear-positive cases, 12 (57.1%) were culture positive and 20 (95.2%) were GeneXpert positive (Table S2). Of the 35 cases that were positive by culture and/or GeneXpert, 14 were positive by both tests, 5 were culture-positive only, and 15 were GeneXpert-positive only (Table S3).
Among the 144 active PTB cases, 120 were male, accounting for 83.3%, and 62 cases aged 60 and above, accounting for 43.1% (Table S4). 55 were re-treated cases, accounting for 38.2%, which was approximately 3 times that of the 2010 national survey (11.8%) and 2022 national surveillance data (10.3%). The proportion of re-treated cases was slightly higher in the Li ethnic group and rural areas (Table S5). 85 (59.0%) of 144 active PTB cases reported no symptoms of PTB, and 17 (47.2%) of 36 bacteriologically confirmed cases reported no symptoms of PTB, both of which were much higher than 2010 national survey (43.1%, 14.2%, Table S6). Among the 59 participants who reported TB-related symptoms, 36 reported cough or sputum production lasting at least three weeks. However, only 6 of these individuals had been notified prior to the survey, while 30 (83.3%) were newly identified in this screening, suggesting a substantial diagnostic delay that may contribute to ongoing transmission. We conducted a comparative analysis of demographic and clinical characteristics between symptomatic and asymptomatic active PTB cases among the 144 identified patients (Table 2). The analysis showed that a history of tuberculosis was the only factor significantly associated with symptom presentation. Specifically, retreated cases had a substantially higher likelihood of being symptomatic compared with new cases (adjusted OR = 5.44, p = 0.0001).
Table 2.
Comparative analysis of demographic and clinical characteristics between symptomatic and asymptomatic active PTB cases
| aOR (95%CI) | p value | |
|---|---|---|
| Sex | ||
| Female | Ref. | |
| Male | 1.03 (0.38, 2.93) | 0.96 |
| Age group | ||
| <35 | Ref. | |
| 35–44 | 1.53 (0.14, 36.0) | 0.74 |
| 45–54 | 1.65 (0.17,36.8) | 0.69 |
| 55–64 | 0.89 (0.09, 20.3) | 0.93 |
| 65–74 | 2.9 (0.29, 66.7) | 0.4 |
| ≥75 | 1.40 (0.12, 35.2) | 0.8 |
| Area | ||
| Rural | Ref. | |
| Urban | 1.63 (0.73, 3.69) | 0.23 |
| Ethnic group | ||
| Han | Ref. | |
| Li | 1.23 (0.54, 2.80) | 0.61 |
| Others | 1.73 (0.08, 20.2) | 0.67 |
| TB_history | ||
| Initial | Ref. | |
| Re-treated | 5.44 (2.34, 13.4) | 0.0001 |
Estimates of the prevalence of active, smear-positive and bacteriologically confirmed PTB are shown in Table 3. The crude prevalence of active PTB was 426 (95% CI 362–502), smear-positive PTB was 62 (95% CI 41–95) per 100 000 people and bacteriologically confirmed PTB was 106 (95% CI 77–148) per 100 000 people. The weighted prevalence of active PTB was 355 (95% CI 351–359), smear-positive PTB was 63 (95% CI 61–65) per 100 000 people and bacteriologically confirmed PTB was 96 (95% CI 94–99) per 100 000 people (Table 3). From 2010 to 2023, the annual decrease rate of active PTB is 3.4%, and the annual decrease rate of smear-positive PTB is 7.2%, both of which were higher than the decrease rates between 1990 and 2010 (2.1%, 2.9%).
Table 3.
Crude and weighted prevalence of active, smear-positive, and bacteriologically confirmed pulmonary tuberculosis in Hainan
| Active pulmonary tuberculosis | Smear-positive pulmonary tuberculosis | Bacteriologically confirmed pulmonary tuberculosis | |||||
|---|---|---|---|---|---|---|---|
| Crude | Estimated | Crude | Estimated | Crude | Estimated | ||
| 1990 | Prevalence | - | 826 | - | 302 | - | - |
| 2010 | Prevalence | - | 539 | - | 167 | - | - |
| 2023 | Cases Number | 144 | 28605 | 21 | 5100 | 36 | 7775 |
| Prevalence | 426 (362, 502) | 355 (351, 359) | 62 (41, 95) | 63 (61, 65) | 106 (77, 148) | 96 (94, 99) | |
| Sex | |||||||
| Male | Cases Number | 120 | 24417 | 16 | 4037 | 29 | 6622 |
| Prevalence | 767 (642, 917) | 575 (568, 583) | 102 (63, 166) | 95 (92, 98) | 185 (129, 266) | 156 (152, 160) | |
| Female | Cases Number | 24 | 4188 | 5 | 1063 | 7 | 1153 |
| Prevalence | 132 (89, 197) | 110 (106, 113) | 28 (12, 66) | 28 (26, 30) | 39 (19, 80) | 30 (28, 32) | |
| Age group (years) | |||||||
| <35 | Cases Number | 4 | 1701 | 1 | 357 | 1 | 357 |
| Prevalence | 70 (27, 181) | 59 (56, 62) | 18 (3, 99) | 12 (11, 14) | 18 (3, 99) | 12 (11, 14) | |
| 35–44 | Cases Number | 17 | 4914 | 4 | 1264 | 7 | 2131 |
| Prevalence | 277 (161, 442) | 316 (307, 325) | 65 (18, 167) | 81 (77, 86) | 114 (46, 235) | 137 (131, 143) | |
| 45–54 | Cases Number | 40 | 9415 | 6 | 2215 | 11 | 3175 |
| Prevalence | 556 (397, 756) | 634 (621, 647) | 83 (31, 181) | 149 (143, 156) | 152 (76, 273) | 214 (207, 221) | |
| 55–64 | Cases Number | 42 | 7055 | 8 | 1057 | 9 | 1102 |
| Prevalence | 555 (401, 750) | 651 (636, 667) | 106 (46, 208) | 98 (92, 104) | 119 (54, 226) | 102 (96, 108) | |
| 65–74 | Cases Number | 27 | 3537 | 1 | 63 | 3 | 414 |
| Prevalence | 524 (346, 762) | 565 (547, 584) | 19 (5, 108) | 10 (8, 13) | 58 (12, 170) | 66 (60, 73) | |
| ≥75 | Cases Number | 14 | 1983 | 1 | 144 | 5 | 596 |
| Prevalence | 690 (378, 1155) | 465 (445, 486) | 49 (1, 274) | 34 (28, 40) | 246 (80, 574) | 140 (129, 152) | |
| Ethnic group | |||||||
| Han | Cases Number | 85 | 16954 | 11 | 3041 | 18 | 4351 |
| Prevalence | 334 (271,413) | 268 (264, 272) | 43 (24, 77) | 48 (46, 50) | 71 (45, 112) | 69 (67, 71) | |
| Li | Cases Number | 56 | 11335 | 9 | 1912 | 16 | 3245 |
| Prevalence | 724 (557, 939) | 716 (703, 729) | 116 (61, 221) | 121 (115, 126) | 207 (127, 336) | 205 (198, 212) | |
| Others | Cases Number | 3 | 316 | 1 | 147 | 2 | 179 |
| Prevalence | 483 (164, 1411) | 211 (189, 235) | 161 (28, 906) | 98 (84, 116) | 322 (88, 1167) | 120 (104, 139) | |
| Area | |||||||
| Urban | Cases Number | 19 | 5385 | 5 | 1997 | 7 | 2665 |
| Prevalence | 221 (141, 345) | 197 (192, 202) | 58 (25, 136) | 73 (70, 76) | 81 (39, 168) | 97 (94, 101) | |
| Rural | Cases Number | 125 | 23220 | 16 | 3103 | 29 | 5110 |
| Prevalence | 497 (417, 591) | 435 (430, 441) | 64 (24, 78) | 58 (56, 60) | 115 (80,165) | 96 (93, 98) | |
The estimated prevalence of active PTB showed an overall pattern of increasing with age and then declining, peaking in the 55–64 year age group (651 per 100,000). However, age-specific trends differed by sex (Fig. 3A). Among men, the pattern mirrored the overall trend, with prevalence rising and then falling, and reaching a peak in the 55–64 year age group (1,144 per 100,000). In contrast, the prevalence among women continued to increase with age and peaked later, in the 65–74 year age group (921 per 100,000). In all age groups except 25–34 years, the estimated prevalence of active PTB was higher in men than in women. For bacteriologically confirmed PTB, the estimated prevalence also followed an overall pattern of increasing and then decreasing with age. The age-specific trends for both men and women were consistent with the overall pattern, with the highest prevalence observed in the 45–54 year age group, which occurred earlier than the peak age for active PTB (Fig. 3B). Additionally, the estimated prevalence of active and bacteriologically confirmed PTB was substantially higher in the Li ethnic group. The estimated prevalence of active PTB was substantially higher in rural areas, but the estimated prevalence of bacteriologically confirmed PTB was similar between urban and rural areas. Stratified analysis by ethnicity and area of residence showed no significant difference in active PTB prevalence between Li and Han participants in urban areas, whereas in rural areas the prevalence was significantly higher among the Li population, suggesting that both rural residence and Li ethnicity may jointly contribute to the elevated TB burden (Table S7).
Fig. 3.
Age-specific prevalence of (A) active pulmonary tuberculosis and (B) bacteriologically confirmed pulmonary tuberculosis stratified by sex in our Hainan survey
Discussion
Between 2010 and 2023, the prevalence of active PTB among individuals aged 15 years and older in Hainan province decreased by 34%, and the prevalence of smear-positive PTB decreased by 62%. However, the prevalence of PTB remains high in Hainan province. Although the prevalence of smear-positive PTB appears to have decreased significantly, it remains close to the average national prevalence in 2010 (66/100,000) [3]. Furthermore, findings from our survey show a regional disparity in prevalence within the province. The prevalence of active PTB in rural areas was 1.7 times higher than that in urban areas. These disparities reflect the levels of economic development. Regions with slow economic development tend to have few financial resources, few qualified health-care workers, and weak public health infrastructure, which are known to be associated with high tuberculosis burden [15, 16]. Additionally, people in rural areas have low education levels, resulting in weak awareness of health [17]. There were 3 clusters in rural areas with very high prevalence in this survey, which was higher than 1000 per 100 000 people. One of them was 2812 per 100 000 people. Further investigation is needed into the reasons for the high prevalence in these places, such as whether there were clusters of infections and the accessibility of local health services to address the regional disparities, which exist both within and across the provinces.
The tuberculosis prevalence varies among different populations. Men were 5 times more likely to have active PTB than were women in Hainan. Sex disparities in tuberculosis prevalence have been observed in many surveys. The effect of smoking, inequalities in socioeconomic status, differences in access to health care, and hormone-related differences in immunity between sexes have been reported in previous studies [18, 19]. The age-specific prevalence of active pulmonary tuberculosis (PTB) showed an overall pattern of increasing with age and then declining, with the highest prevalence observed among individuals aged 55–64 years. However, sex-specific patterns differed. Among men, the trend mirrored the overall pattern, peaking in the 55–64 age group, whereas among women, prevalence continued to rise with age and reached its highest level in those aged 65–74 years. Notably, the prevalence of bacteriologically confirmed PTB peaked earlier, in the 45–54 age group, in both sexes. This pattern is different from that seen in the 2010 national survey. Another age-period-cohort analysis of the incidence of active pulmonary tuberculosis in southwestern China also indicated that PTB incidence increased in populations aged 50–54 years across the study period [20]. Together, these findings indicate that active case-finding strategies should not only prioritize the elderly but also pay close attention to middle-aged adults, particularly men, who may contribute disproportionately to ongoing transmission.
We also observed marked ethnic differences in prevalence in this survey. Prevalence among the Han ethnic group in Hainan was similar to that in the general population in the more developed eastern region of China in 2010 [3]. However, individuals of the Li ethnic group were 2.7 times more likely to have active pulmonary tuberculosis than were the Han ethnic group. Stratified analysis further showed that in urban areas there was no significant difference between Li and Han populations, whereas in rural areas the prevalence among the Li population was substantially higher than among the Han population. Considering that the majority of the Li ethnic group reside in rural areas, this suggests a potential interaction between ethnicity and place of residence, where the combined effects of rural living conditions and ethnic-specific socioeconomic or cultural factors may further elevate TB risk. Ethnic disparities in prevalence have also been observed in other surveys [21]. Low socioeconomic status, poverty, and delayed diagnosis and treatment are potential reasons for the high prevalence among the Li ethnic groups in Hainan [22]. In addition, the prevalence rates of tobacco and alcohol use in Li male villagers are higher than those of the national average and other ethnic minorities in China, which may also cause a high prevalence of PTB [23]. However, we were unable to fully disentangle the underlying social and biological mechanisms because detailed behavioral and environmental data were not collected. Further studies exploring the interaction between ethnicity, living environment, and access to health services are therefore warranted.
Among the 144 active PTB cases identified in this survey, 59 reported symptoms of tuberculosis, 36 of which reported cough or sputum production for at least the past 3 weeks or more. Of the 36 cases, only 6 were notified before this screening, while 30 (83.3%) were newly identified in this survey. Their diagnosis was delayed by at least 21 days (i.e. 3 weeks), which may further cause the spread of tuberculosis in the population [24, 25]. Moreover, this survey also found an increase in the proportion of asymptomatic cases. Of the 144 active PTB cases, 85 (including 17 bacteriologically confirmed PTB) reported no symptoms of PTB, accounting for 59.0%, which was higher than that of the national survey in 2010 (43.1%) and 55 were re-treated cases, accounting for 38.2%, which was approximately 3 times that of the 2010 national survey (11.8%) and 2022 national surveillance data (10.3%). Notably, among asymptomatic bacteriologically confirmed cases, only one had a negative chest X-ray, indicating that most of these otherwise missed infectious cases could still be identified through radiographic screening. Further analysis showed that asymptomatic presentation was more common among newly diagnosed patients, whereas re-treated patients were more likely to present with symptoms. This may reflect possible differences in disease progression or immune response between new and previously treated cases. Taken together, these findings suggest that TB prevention and control in Hainan should be strengthened through active case finding using chest X-ray screening combined with rapid molecular diagnostics, together with improved patient management and treatment quality [10].
In addition, some discordance was observed among different bacteriological diagnostic methods. For example, 14 cases were culture-negative but GeneXpert-positive, and 20 cases were GeneXpert- or culture-positive but smear-negative. These discrepancies may be related to differences in bacterial load, specimen quality, bacillary viability, or test sensitivity. The higher positivity of GeneXpert MTB/RIF than culture among smear-positive cases further highlights the value of rapid molecular diagnostics with higher sensitivity in large-scale screening to improve case detection [26].
This survey has several limitations. First, the survey did not use newer WHO-recommended diagnostic approaches such as Xpert Ultra and liquid culture (MGIT). Given the sensitivity gap between these newer technologies and the methods used in this survey, the prevalence of bacteriologically confirmed PTB may have been underestimated, particularly among paucibacillary or asymptomatic cases [27]. Second, sputum examination among chest X-ray screening positives was based on expert-reviewed radiographic abnormalities suggestive of PTB rather than all field-detected abnormalities. This narrower screening threshold may have reduced the sensitivity of radiographic screening and contributed to under-ascertainment of bacteriologically confirmed PTB. Finally, the eligibility criteria required participants to have resided in the household for at least six months, which likely led to under-representation of highly mobile and migrant populations. As a result, the estimated prevalence primarily reflects the burden of PTB among the resident adult population and may underestimate the overall burden in settings with substantial population mobility.
The high prevalence of active PTB in Hainan province, while showing a recent decline, underscores persistent challenges in the path to TB elimination. Significant disparities across sex, age, geography, and ethnicity, coupled with a high proportion of re-treated and asymptomatic cases, reveal critical gaps in the current passive surveillance system. To address this, more effective and targeted active case-finding strategies are urgently needed, such as those combining chest X-ray screening with rapid molecular diagnostics. Future efforts must prioritize high-risk groups, particularly men aged 45 years and above, the Li ethnic group, and rural residents, through enhanced active surveillance. Strengthening these initiatives is essential to improve early diagnosis and treatment, and to ultimately accelerate TB control in Hainan [28].
Conclusion
This population-based survey provides updated and robust evidence that, despite a substantial decline since 2010, the burden of PTB in Hainan Province remains high. Pronounced disparities by sex, age, geography, and ethnicity highlight persistent structural and health system inequities. The high proportions of re-treated and asymptomatic cases indicate ongoing challenges in treatment quality, delayed diagnosis, and reliance on passive case detection. These findings underscore the need to strengthen targeted community-based active case-finding strategies, particularly among high-risk populations such as middle-aged and older men, rural residents, and the Li ethnic group. More effective screening technologies, together with improved treatment management and follow-up, will be critical to reducing transmission and accelerating progress toward tuberculosis elimination in Hainan Province.
Electronic supplementary material
Below is the link to the electronic supplementary material.
Author contribution
YZ and DY designed the study. CX and XL organized and implemented investigations at the study sites. SP and XL did data management and quality control. SP and XL analyzed data and wrote the report. All authors contributed to review and revision and have seen and approved the final version of the manuscript.
Funding
National Science and technology Major Project of China 2025ZD01901000, China CDC-Tuberculosis Control and Prevention Project (2528). Public Health Personnel Training Support Program (01056).
Data availability
The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.
Declarations
Ethics approval and consent to participate
The survey protocol was approved by the Hainan Center for Disease Control and Prevention Ethics Review Committee. All study procedures were performed in accordance with relevant guidelines and regulations, including the Declaration of Helsinki. Individual written informed consent, or assent together with parent or guardian consent for participants younger than 18 years, was obtained at survey enrolment. All data were anonymized prior to analysis. This manuscript does not report on or involve the use of any animal data or tissue.
Consent for publication
Not applicable.
Competing of interests
We declare no competing interests.
Footnotes
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Changfu Xiong and Shaojun Pei these authors contribute equally.
Yanlin Zhao and Dapeng Yin contributed equally to this work.
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.