https://ojs.wpro.who.int/ 1WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931 Surveillance Report I n 2021, there were an estimated 10.6 million cases and 1.4 million deaths from tuberculosis (TB) globally, with 14% of cases in the Western Pacific Region.1 The first national TB prevalence survey in Mongolia was conducted in 2014–2015; it estimated the pulmonary TB prevalence to be 441 per 100 000 population, and the prevalence of all forms of TB to be 757 per 100 000 population.2 Based on the newly available data, TB incidence was re-estimated by the World Health Organization (WHO) to be 437 (uncertainty range: 224–719) per 100 000 population,3 ranking Mongolia among the 30 countries with the highest TB incidence in the world.1 Mongolia’s National Tuberculosis Programme (NTP) surveillance system is a combination of a paper-based aggregated system and a digital case-based system that covers TB cases from screening through to completion of treatment. Subnational analysis of key TB indicators and trends over time is useful for programmatic decision- making and helps to increase programmatic impact where interventions can be tailored to local dynamics.4,5 Through analysis of routine surveillance data, we report TB epidemiology and key programmatic indicators at the national and subnational levels for 2015–2019. METHODS Description of the surveillance system In Mongolia, TB cases can be detected through passive case detection, in which symptomatic individuals attend- ing primary care facilities are screened for TB. Those who present with a persistent cough are referred to a TB dispensary for a diagnostic evaluation by sputum smear microscopy. If smear-positive, the patient is registered as a confirmed TB case and is started on treatment; if smear-negative, a chest X-ray is conducted. Since 2017, the Xpert MTB/RIF test is also conducted where possible. a National Tuberculosis Programme, Ministry of Health, Ulaanbaatar, Mongolia. b Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru. c World Health Organization Regional Office for the Western Pacific, Manila, Philippines. d World Health Organization Representative Office for Mongolia, Ulaanbaatar, Mongolia. Published: 24 March 2023 doi: 10.5365/wpsar.2023.14.1.931 Mongolia has a high tuberculosis (TB) burden. Data from routine paper-based surveillance were used to describe the epidemiology of TB in Mongolia; the data included testing presumptive TB cases, TB notifications, drug-resistant cases, treatment outcomes and notifications in prisoners. The proportion of the population tested for TB increased between 2015 and 2019. The number and rate per 100 000 population of TB notifications decreased between 2015 and 2018 and then increased in 2019. Most TB notifications in 2019 were in the capital, Ulaanbaatar (59.3%), followed by the central (16.8%), Khangai (10.4%), east (8.5%) and west (5.0%) regions. About half of TB notifications nationally were bacteriologically confirmed (45.4% in 2015, 48.1% in 2019), with the proportion of bacteriologically confirmed TB per province or district varying from 0% to 66%. High TB notification rates were observed in 2019 for males aged 15–54 years (202 per 100 000 population) and females aged 15–34 years (190 per 100 000 population). Treatment success for all forms of TB was 90% in 2019 but was below the 90% target for bacteriologically confirmed cases. Between 2015 and 2019, the number of RR/MDR-TB notifications ranged from 265 to 211. The Mongolian National Tuberculosis Programme needs to continue its efforts in TB control, to further increase the programmatic impact and reduce the TB burden. It is recommended that Mongolia continue to increase TB screening, the use of Xpert testing, contact investigations and preventive treatments, and targeting interventions to the high-burden areas identified in this subnational analysis. Epidemiology of tuberculosis in Mongolia: analysis of surveillance data, 2015–2019 Tsolmon Boldoo,a Larissa Otero,b,c Borgil Uranchimeg,a Anuzaya Purevdagva,d Temuulen Enebish,a Oyunchimeg Erdenee,a Tauhid Islamc and Fukushi Morishitac Correspondence to Larissa Otero (email: larissaotero@gmail.com) WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931 https://ojs.wpro.who.int/2 Boldoo et alTuberculosis epidemiology in Mongolia Corp, 16.0, College Station, TX, United States of America) was used for analysis. RR/MDR-TB treatment outcomes were analysed for the 2017 cohort only because in most cases treatment duration is 24 months. RESULTS Testing of presumptive TB cases The proportion of the population tested for TB increased from 2015 to 2019, as did the proportion of the popula- tion tested by X-ray (Fig. 1). In 2019, 85.7% (n = 4664/5422) of registered TB contacts were tested, with 4.0% (n = 185) diagnosed with TB. These were slight increases compared with 2015 (81% and 3.3%, respectively). The proportion of child contacts (aged 0–14 years) who were TST-positive was 20.2% (n = 424/2102) in 2019, an increase from 16.7% (n = 324/1936) in 2015. The proportion of TST-positive child contacts who started on TB-preventive treatment was 71.2% (n = 302/424) in 2019, an in- crease from 46.0% (n = 149/324) in 2015. The smear positivity rate was 8% (n = 2376/28 753) in 2019, a decrease from 12% (n = 2812/23 703) in 2015. This varied subnationally, from 5% (n = 570/14 301) in 21 provinces to 10% (n = 3565/36 714) in Ulaanbaatar. Of the 17 854 Xpert MTB/RIF tests done in 2019, 3070 (17.2%) were MTB-positive, of which 261 (8.5%) were RR-TB. Case notifications by patient type The number and rate of notified TB cases decreased between 2015 and 2018, and then increased in 2019 (Fig. 2A). The increase in 2019 was observed for bac- teriologically confirmed TB, extra-pulmonary TB and clinically diagnosed TB (Fig. 2B). In 2019, there were 133 per 100 000 population new and relapse TB cases notified, representing 31% of the WHO-estimated incident cases (n = 14 000).7 Of all TB notifications in 2019, 85.4% (n = 3624) were new cases, 11.0% (n = 465) were relapse cases, 3.4% (n = 146) were cases requiring retreatment after treat- ment failure or LTFU and 0.2% (n = 9) had unknown TB treatment history. Cases can also be detected through screening of close contacts of TB cases or through active case finding in high-risk groups (e.g. people living with HIV, miners and prisoners). Contacts and high-risk groups are tested through symptom screening and chest X-ray, and the tuberculin skin test (TST) is also used for child contacts. Contacts and those from high-risk groups who are posi- tive on screening are referred for diagnostic evaluation to TB dispensaries. All cases are registered on paper forms at the TB dispensaries; staff then compile aggregate monthly re- ports of notifications and treatment outcomes and send them to the provincial level, where they are aggregated each quarter and sent to the national level, where they are collated and reviewed for timeliness, completeness and accuracy by an NTP statistician. The system uses standardized TB collection forms updated with the latest WHO reporting framework for TB case detection and treatment outcomes.6 From 2018, the digital case-based system, TUBIS, has been used to collect individual case data, capturing 90% of the data from the paper-based system. Data analysis National TB surveillance data for 2015–2019 were retro- spectively analysed, using data sourced from the aggre- gated paper-based system. Rates were calculated using population projections from the National Statistical Office of Mongolia, and vital and civil registration from the 2010 census for the denominator. Analysis included testing of presumptive TB cases and number of notifications by age, sex, patient type and location, drug-resistant cases, treatment outcomes and notifications in prisoners. Patient type was classified into bacteriologically confirmed TB, extra-pulmonary TB, clinically diagnosed TB and other previously treated TB. Subnational analysis was conducted for the east, central, Khangai and west regions, plus the capital Ulaanbaatar. Regions were fur- ther analysed by their provinces, and Ulaanbaatar by its districts. Drug resistance categories included cases with mono-drug and poly-drug resistance, and cases with rifampicin resistance or multidrug resistance (RR/MDR). Treatment outcomes for bacteriologically confirmed TB cases included treatment success, treatment failure, death and loss to follow-up (LTFU). Stata software (Stata WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931https://ojs.wpro.who.int/ 3 Tuberculosis epidemiology in MongoliaBoldoo et al Case notifications by sex and age in 2019 The highest numbers of case notifications in 2019 were seen in males aged 15–54 years and females aged 15–34 years (Fig. 6). This distribution varied by TB type: 57.2% of new cases were male, with a mean (± standard deviation [SD]) age of 33 (± 17.3) years, whereas 66.9% of relapse cases were male, with a mean age of 40 (± 13.9) years. In 2019, 9.1% (n = 415) of TB notifications were aged under 15 years and 2.7% (n = 121) were aged under 5 years. Subnational analysis showed large variations in the proportion of cases by age group and among children, with some provinces having no paediatric TB notifications or only small numbers of such notifications (Fig. 7). Drug-resistant TB Between 2015 and 2019, the number of RR/MDR-TB notifications ranged from 265 to 211 (Fig. 8). In 2019, 211 RR/MDR-TB cases were diagnosed; of these, 92% (n = 193) were enrolled in second-line TB treatment, an increase from 85% of the 265 cases in 2015. Seven extensively drug-resistant TB (XDR-TB) cases were diagnosed in 2019. Of the 211 RR/MDR-TB cases, 46.9% (n = 99) were new cases and 41.7% (n = 88) were relapse and The combined proportion of cases requiring retreatment and relapse cases increased from 13.2% (n = 652/4935) in 2015 to 14.4% (n = 611/4244) in 2019. The proportion of extra-pulmonary TB cases de- creased from 41.9% (n = 2068/4935) in 2015 to 35.7% (n = 1513/4244) in 2019. Bacteriologically confirmed TB cases comprised about half of all TB cases (45.5% [n = 2244/4935] in 2015 and 48.1% [n = 2041/49244] in 2019). Of the pulmonary cases, 74.8% (n = 2043/2731) were bacteriologically confirmed in 2019. Subnational case notifications Most notifications in 2019 occurred in Ulaanbaatar, fol- lowed by the central (excluding Ulaanbaatar), Khangai, east and west regions (Table 1). The notification rate increased in the east region from 2017, and in the other four regions from 2018 (Fig. 3A). The proportion of cases that were bacteriologically confirmed increased from 2016 in Ulaanbaatar and Khangai, from 2017 in central and from 2018 in the west region (Fig. 3B). No- tification rates per 100 000 varied substantially across provinces in 2019, ranging from 37 to 172 (Fig. 4). In 2019, the proportion of bacteriologically confirmed TB per province or district within each region varied sub- stantially (Ulaanbaatar: 0–51%, east: 34–60%, central: 43–66%, Khangai: 38–57% and west: 39–58%) (Fig. 5). Fig. 1. Proportion of the population examined for TB by test, Mongolia, 2015–2019 9.6 9.4 13.6 14.1 15.2 5.6 5.8 8.3 8.7 8.2 1.1 1.1 1.2 1.2 1.2 0.1 0.1 0.1 0.1 0.2 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 2015 2016 2017 2018 2019 Pr op or tio n of th e po pu la tio n Year Examined by any method Screened by X-ray Tested by smear Tested by culture or Xpert WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931 https://ojs.wpro.who.int/4 Boldoo et alTuberculosis epidemiology in Mongolia Treatment outcomes The proportion of TB notifications with treatment suc- cess increased from 88.8% in 2015 to 90.0% in 2019. The proportion of deaths decreased from 4.6% in 2015 to 2.5% in 2019. The proportion of cases that were LTFU was stable (4.6% in 2018), as was the proportion other previously treated cases. Of new RR/MDR-TB cases, 40.4% were female, similar to the proportion seen in all TB notifications. The mean age for new RR/ MDR-TB cases was 34.9 (± 18.4) years, similar to the proportion seen in all TB notifications (33 ± 17.3). The mean age for relapse and other previously treated RR/ MDR cases was 41 (± 14.3). Fig. 2. (A) Number and rate per 100 000 population of TB notifications, and (B) TB notification rates per 100 000 population by type of TB, Mongolia, 2015–2019 EPTB: extra-pulmonary tuberculosis. 58.4 45.8 20.9 4.7 0 10 20 30 40 50 60 70 80 2015 2016 2017 2018 2019 TB n ot if ic at io n ra te p er 1 00 0 00 p op ul at io n Bacteriologially confirmed, new and relapse EPTB, new and relapse Clinically diagnosed, new and relapse Other previously treated 4843 4596 4356 3999 4190 160 149 138 125 128 0 20 40 60 80 100 120 140 160 180 3800 4000 4200 4400 4600 4800 5000 2015 2016 2017 2018 2019 TB n ot if ic at io n ra te p er 1 00 0 00 p op ul at io n N um be r of T B n ot if ic at io ns Notifications Rates 58.4 45.8 20.9 4.7 0 10 20 30 40 50 60 70 80 2015 2016 2017 2018 2019 TB n ot if ic at io n ra te p er 1 00 0 00 p op ul at io n Bacteriologially confirmed, new and relapse EPTB, new and relapse Clinically diagnosed, new and relapse Other previously treated 4843 4596 4356 3999 4190 160 149 138 125 128 0 20 40 60 80 100 120 140 160 180 3800 4000 4200 4400 4600 4800 5000 2015 2016 2017 2018 2019 TB n ot if ic at io n ra te p er 1 00 0 00 p op ul at io n N um be r of T B n ot if ic at io ns Notifications RatesA B WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931https://ojs.wpro.who.int/ 5 Tuberculosis epidemiology in MongoliaBoldoo et al Table 1. Number and rate per 100 000 population of TB notifications by treatment history and proportion of retreatment and extra-pulmonary TB by province or district, Mongolia, 2019 Region and provinces or districts Population Notifications (N) Rates per 100 000 population Percentage (%) New and relapse Previously treated New and relapse Previously treated Retreatment Extra- pulmonary TB Ulaanbaatar 1 515 593 2359 127 156 8 5.1 37.1 Baganuur 28 570 25 0 88 0 0 28.0 Bayangol 225 840 318 7 141 3 2.2 48.0 Bayanzurkh 361 689 638 52 176 14 7.5 48.0 Nalaih 37 659 40 5 106 13 11.1 37.8 Songinokhairkhan 327 580 581 30 177 9 4.9 38.3 Sukhbaatar 144 409 154 0 107 0 0 35.7 Khan-Uul 187 278 246 10 131 5 3.9 25.8 Chingeltei 148 977 304 16 204 11 5.0 38.4 Bagakhangai 4123 0 0 0 0 0 0 East 221 764 348 7 157 3 2 30.7 Khentii 77 493 139 1 179 1 0.7 40.0 Dornod 81 519 112 5 137 6 4.3 20.5 Sukhbaatar 62 752 97 1 155 2 1.0 29.6 Central 515 025 696 7 135 1 1 31.0 Selenge 110 757 174 2 157 2 1.1 25.0 Umnugovi 67 955 36 0 53 0 0 44.4 Tuv 94 956 173 2 182 2 1.1 36.6 Darkhan-Uul 106 470 172 2 162 2 1.1 29.3 Govisumber 17 862 18 0 101 0 0 27.8 Dundgov 46 866 31 0 66 0 0 51.6 Dornogovi 70 159 92 1 131 1 1.1 23.7 Khangai 604 784 427 7 71 1 2 50.5 Orkhon 106 810 90 4 84 4 4.3 52.2 Uvurkhangai 116 922 61 0 52 0 0 58.8 Bayankhongor 88 514 59 0 67 0 0 51.3 Arkhangai 95 857 58 0 61 0 0 58.0 Khuvsgul 134 530 111 3 83 2 2.6 44.7 Bulgan 62 151 48 0 77 0 0 40.0 West 410 507 209 3 51 1 1 39.2 Uvs 83 766 46 1 55 1 2.1 23.4 Bayan-Ulgii 106 810 44 0 41 0 0 52.3 Zavkhan 72 801 36 2 49 3 5.3 52.6 Khovd 89 021 50 0 56 0 0 36.0 Gobi-Altai 58 109 33 0 57 0 0 33.3 WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931 https://ojs.wpro.who.int/6 Boldoo et alTuberculosis epidemiology in Mongolia Fig. 3. (A) TB notification rates per 100 000 population by region, and (B) proportion of TB cases that were bacteriologically confirmed by region, Mongolia, 2015–2019 A B 164 160 161 72 52 0 50 100 150 200 250 2015 2016 2017 2018 2019 N ot if ic at io n ra te p er 1 00 0 00 p op ul at io n Year Ulaanbaatar East Central Khangai West 55 45 0 10 20 30 40 50 60 70 2015 2016 2017 2018 2019 Pr op or ti on o f ba ct er io lo gi ca lly c on fi rm ed c as es Year Ulaanbaatar East Central Khangai West 164 160 161 72 52 0 50 100 150 200 250 2015 2016 2017 2018 2019 N ot if ic at io n ra te p er 1 00 0 00 p op ul at io n Year Ulaanbaatar East Central Khangai West 55 45 0 10 20 30 40 50 60 70 2015 2016 2017 2018 2019 Pr op or ti on o f ba ct er io lo gi ca lly c on fi rm ed c as es Year Ulaanbaatar East Central Khangai West Fig. 4. Map of TB notification rates per 100 000 population by province, Mongolia, 2019 ! 37–45 46–62 63–90 91–139 140–172 WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931https://ojs.wpro.who.int/ 7 Tuberculosis epidemiology in MongoliaBoldoo et al Fig. 5. Proportion of TB cases that were bacteriologically confirmed by district in Ulaanbaatar (A) and by province in the east (B), central (C), Khangai (D) and west (E) regions, Mongolia, 2015–2019 51 0 0 10 20 30 40 50 60 70 80 2015 2016 2017 2018 2019 Pr op or ti on o f ba ct er io lo gi ca lly c on fi rm ed c as es Baganuur Bayangol Bayanzürkh Nalaih Songinokhair khan Sukhbaatar district Khan Uul Chingeltei Bagakhangai 51 0 0 10 20 30 40 50 60 70 80 2015 2016 2017 2018 2019 Pr op or ti on o f ba ct er io lo gi ca lly c on fi rm ed c as es Baganuur Bayangol Bayanzürkh Nalaih Songinokhair khan Sukhbaatar district Khan Uul Chingeltei Bagakhangai 60 34 0 10 20 30 40 50 60 70 80 2015 2016 2017 2018 2019 Pr oo po rt io n of b ac te ri ol og ic al ly c on fi rm ed c as es Sukhbaatar Dornod Khentii 66 43 0 10 20 30 40 50 60 70 80 2015 2016 2017 2018 2019 Pr op or ti on o f ba ct er io lo gi ca lly c on fi rm ed c as es Govisumber Darkhan-Uul Dornogovi Dundgov Umnugovi Selenge Tuv Ulaanbaatar 38 57 0 10 20 30 40 50 60 70 80 2015 2016 2017 2018 2019 Pr op or ti on o f ba ct er io lo gi ca lly c on fi rm ed c as es Arkhangai Bayankhongor Bulgan Orkhon Uvurkhangai Khuvsgul 39 58 0 10 20 30 40 50 60 70 80 2015 2016 2017 2018 2019 Pr op or ti on o f ba ct er io lo gi ca lly c on fi rm ed c as es Bayan Ulgii Gobi Altai Zavkhan Uvs Khovd A C E B D WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931 https://ojs.wpro.who.int/8 Boldoo et alTuberculosis epidemiology in Mongolia treated, one (14.3%) failed, three (42.9%) died and one (14.3%) was LTFU. TB in prisoners TB notifications in prisoners decreased from 92 (1.9%) in 2015 to 54 (1.3%) in 2019. A higher proportion of bacteriologically confirmed cases (64.3%) and relapse cases (25.9%) were notified than from the national data (58.5% and 11%, respectively). DISCUSSION The results of this TB surveillance analysis demonstrate the progress of the NTP in Mongolia, with increases in the proportion of the population screened for TB, bacteriological confirmation, treatment success and TB-preventive treatment in children. Intensification of case-finding activities through the expansion of Xpert of those not evaluated (0.4% in 2019). Since 2016, the treatment success rate has been above 90% for all types of TB except for bacteriologically confirmed TB cases (85.4%). The death rate was highest among relapse cases (4.8%). In 2019, the treatment success rate for bacte- riologically confirmed cases was less than 90% in three provinces (Dornogovi, Khovd and Orkhon) and Ulaanbaatar (Fig. 9). Ulaanbaatar reported relatively poor treatment outcomes compared with other prov- inces; 8% of bacteriologically confirmed cases were LTFU, 5% failed and 4% died. In 2017, 56% (n = 122/216) of RR/MDR-TB patients enrolled in treatment were successfully treated, a slight decrease from 60% in 2015–2016. The LTFU rate among RR/MDR-TB cases increased from 16% in 2016 to 26% in 2017. Of seven XDR-TB cases in the 2017 patient cohort, two (28.6%) were successfully Fig. 6. Number and rate per 100 000 population of TB notifications by sex and age group, Mongolia, 2019 0 50 100 150 200 250 300 0 100 200 300 400 500 600 0–4 5–14 15–24 25–34 35–44 45–54 55–64 ≥65 N ot ifi ca ti on ra te p er 1 00 0 00 p op ul at io n N um be r of n ot ifi ca ti on s Age group Female Male Female rate Male rate WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931https://ojs.wpro.who.int/ 9 Tuberculosis epidemiology in MongoliaBoldoo et al Fig. 7. Proportion of TB notifications by age group and province, Mongolia, 2019 21.0 8.0 5.0 2.0 13.0 5.0 5.0 4.2 3.0 20.0 7.0 7.0 5.0 5.0 3.0 2.0 7.0 6.0 4.0 11.0 21.2 30.6 29.7 31.9 14.3 18.3 26.2 17.7 22.9 12.9 20.3 25.7 29.0 23.3 38.1 14.0 27.0 22.7 25.9 22.1 26.2 23.2 21.2 10.2 13.5 23.4 38.1 28.7 19.7 21.0 12.5 26.7 23.7 18.3 22.6 20.6 4.8 31.0 24.3 20.5 19.4 22.1 21.3 24.2 9.6 28.6 16.2 21.3 26.2 11.3 13.1 19.4 20.8 19.8 16.9 12.6 16.1 17.5 19.0 14.0 14.6 11.4 20.4 15.0 17.7 15.9 13.5 6.1 13.5 6.4 11.9 13.9 19.7 19.4 18.8 15.8 23.7 11.4 19.4 20.1 28.6 19.0 14.6 15.9 13.9 20.0 16.3 13.3 9.6 16.3 18.9 6.4 4.8 11.3 13.1 8.1 14.6 13.9 6.8 7.4 6.5 5.8 4.8 6.0 10.8 18.2 10.2 11.4 10.6 8.0 4.4 2.7 8.5 3.5 3.3 9.7 6.3 7.9 8.5 4.6 5.8 11.0 5.4 9.1 2.8 2.9 3.5 4.7 0 10 20 30 40 50 60 70 80 90 100 Khovd Uvs Gobi-Altai Bayan-Ulgii Zavkhan Khuvsgul Arkhangai Uvurkhangai Bulgan Orkhon Bayankhongor Tuv Dundgovi Selenge Govisumber Dornogovi Darkhan-Uul Umnugovi Sükhbaatar Dornod Khentii Ulaanbaatar W es t Kh an ga i Ce nt ra l Ea st Percentage 0–14 15–24 25–34 35–44 45–54 55–64 ≥65 Fig. 8. Number of TB notifications and notification rate per 100 000 population by drug-resistant TB categories, Mongolia, 2015–2019 0 2 4 6 8 10 12 14 16 0 50 100 150 200 250 300 350 400 450 2015 2016 2017 2018 2019 N ot ifi ca tio n ra te p er 1 00 0 00 p op ul at io n N um be r of n ot ifi ca tio ns Year RR/MDR notifications Mono- and poly-DR notifications RR/MDR notification r ate Mono- and poly-DR notification r ate 0 2 4 6 8 10 12 14 16 0 50 100 150 200 250 300 350 400 450 2015 2016 2017 2018 2019 N ot ifi ca tio n ra te p er 1 00 0 00 p op ul at io n N um be r of n ot ifi ca tio ns Year RR/MDR notifications Mono- and poly-DR notifications RR/MDR notification r ate Mono- and poly-DR notification r ate DR: drug resistance; RR/MDR: rifampicin resistance or multidrug resistance. WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931 https://ojs.wpro.who.int/10 Boldoo et alTuberculosis epidemiology in Mongolia The WHO-estimated incidence of RR/MDR-TB for Mongolia was one of the highest among countries in the Western Pacific Region.1 However, the number of RR/ MDR-TB notifications did not increase during the study period, highlighting a case-detection gap that is also found in other countries.4 To respond to the burden of DR-TB, there is an urgent need to increase the coverage of Xpert as an initial diagnostic test and reduce diagnostic delays. The high caseload in younger age groups suggests recent transmission, emphasizing the need to expand and accelerate case detection. Exposure to tobacco and solid fuels for heating has been significantly associated with bacteriological TB,8 which may contribute to the higher rates in these age groups. The proportion of TB in chil- dren varied widely across provinces. As in many settings testing and sustaining treatment success, particularly in Ulaanbaatar, will probably increase the impact of the NTP and reduce the national TB burden. The number and rate of TB notifications decreased in 2015–2018 and increased in 2019, despite increases in screening. Similar trends have also been observed in other high-burden countries such as Cambodia, where estimated TB incidence is declining.4,5 The expansion of X-ray and Xpert testing and the strengthening of the specimen transportation system may have resulted in an increase in notifications and an increased proportion of bacteriological confirmation in 2019. However, WHO estimates that the TB notification system is detecting only 31% of TB cases in the country.1 To fill this gap, the NTP needs to intensify its efforts in screening high-risk populations.7 Fig. 9. Proportion of bacteriologically confirmed TB notifications by treatment outcomes and province, Mongolia, 2019 100.0 100.0 100.0 93.8 85.7 100.0 95.8 95.1 94.4 92.3 73.3 100.0 100.0 100.0 95.8 94.7 90.9 84.7 91.7 91.7 91.4 80.7 3.0 8.0 13.0 2.0 6.0 2.0 4.0 6.0 5.0 6.3 14.3 5.6 6.7 1.4 1.8 6.8 4.2 2.8 2.9 3.6 4.2 6.7 3.5 2.3 6.8 5.6 7.6 2.1 1.0 1.1 2.9 50 55 60 65 70 75 80 85 90 95 100 Zavkhan Gobi-Altai Bayan-Ulgii Uvs Khovd Bulgan Arkhangai Khuvsgul Bayankhongor Uvurkhang ai Orkhon Umnug ovi Govisumber Dundgovi Selenge Darkhan-Uul Tuv Dornogovi Sukhbaatar Khentii Dornod Ulaanbaatar W es t Kh an ga i Ce nt ra l Ea st Percentage Success Failed Died LTFU Not evaluated The black line indicates the WHO 90% target for TB treatment success. LTFU: loss to follow-up. WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931https://ojs.wpro.who.int/ 11 Tuberculosis epidemiology in MongoliaBoldoo et al comparative epidemiological trends and programmatic performance. National and subnational TB programmes can tailor and target interventions addressing local-level issues identified in routine analysis, contributing to end- ing TB by 2030. Acknowledgements The authors wish to thank all health-care workers at the front lines of TB service delivery in Mongolia. The authors extend their thanks to all staff of the national and subnational TB programmes and collaborators, and especially to the WHO Representative Office for Mongolia for their continuous support. Conflicts of interest The authors have no conflicts of interest to declare. Ethics statement Ethical clearance was not required because the analysis was based on routine data with no identifiable informa- tion. Funding This study was funded by the World Health Organization Regional Office for the Western Pacific. References 1. Global tuberculosis report 2022. Geneva: World Health Organization; 2022. Available from: https://apps.who.int/iris/han- dle/10665/363752, accessed 13 November 2022. 2. Report of the first national tuberculosis prevalence survey in Mongolia (2014–2015). Ulaanbaatar: Ministry of Health; 2016. 3. Global Tuberculosis Programme. TB country, regional and global profiles. Geneva: World Health Organization; 2021. Available from: https://worldhealthorg.shinyapps.io/tb_profiles/?_inputs_&entity_ty pe=%22country%22&lan=%22EN%22&iso2=%22MN%22, ac- cessed 21 September 2022. 4. Morishita F, Viney K, Lowbridge C, Elsayed H, Oh KH, Rahevar K, et al. Epidemiology of tuberculosis in the Western Pacific Region: progress towards the 2020 milestones of the End TB Strategy. Western Pac Surveill Response J. 2020;11(4):10–23. doi:10.5365/ wpsar.2020.11.3.002 pmid:34046237 5. Rahevar K, Fujiwara PI, Ahmadova S, Morishita F, Reichman LB. Implementing the End TB Strategy in the Western Pacific Region: translating vision into reality. Respirology. 2018;23(8):735–42. doi:10.1111/resp.13308 pmid:29648691 6. Definitions and reporting framework for tuberculosis – 2013 revi- sion: updated December 2014 and January 2020. Geneva: World Health Organization; 2013. Available from: https://apps.who.int/ iris/handle/10665/79199, accessed 16 June 2022. globally, there is a need to strengthen the capacities of physicians in diagnosing paediatric TB and expand Xpert testing in children to increase correct and timely diagno- ses.1,9 TB among prisoners decreased during the study period, as it did in the previous decade.10 Furthermore, the proportion of relapse cases among prisoners was more than double that of the general population. A decrease in the proportion of deaths of TB cases has improved overall treatment outcomes, but because of persistently high rates of LTFU, bacteriologically con- firmed TB treatment success rates remain below 90%. Addressing physical barriers to TB services for mobile populations (including nomads) and reducing financial barriers may improve health access for vulnerable pa- tients. The low treatment success rate among DR-TB cases needs attention, especially considering the increase in the notification rate of MDR-TB found in the national drug resistance survey in 2017, compared with that in 2007.11 The use of Xpert as a front-line test and the implementation of a shorter all-oral regimen for MDR-TB treatment should be prioritized.12 Our analysis is limited to TB cases diagnosed and reported to the NTP; thus, it does not represent all estimated cases of TB in Mongolia. The 70% case- detection gap estimated at the national level1 is likely to vary between provinces and this was not detected by our analysis. A full transition to the digital case-based system and discontinuing the paper-based system would bolster routine data analysis because individual case data provide more detail than the aggregate data. The Mongolian NTP needs to continue its efforts in TB control to achieve further progress. Expanding and accelerating case detection with Xpert and ensuring the treatment success of bacteriologically confirmed TB would probably reduce the TB burden. Other pri- orities are addressing transmission in men and young adults, and strengthening paediatric TB diagnosis. The focus should be on Ulaanbaatar because it has higher notification rates and suboptimal treatment outcomes, and overcrowding and pollution that increase the risk of transmission. Advancing a multisectoral response is critical to addressing social determinants of TB such as indoor air pollution. TB surveillance data provide an opportunity to conduct subnational analyses, to inform districts of their WPSAR Vol 14, No 1, 2023 | doi: 10.5365/wpsar.2023.14.1.931 https://ojs.wpro.who.int/12 Boldoo et alTuberculosis epidemiology in Mongolia 10. Yanjindulam P, Oyuntsetseg P, Sarantsetseg B, Ganzaya S, Amgalan B, Narantuya J, et al. Reduction of tuberculosis burden among prisoners in Mongolia: review of case notification, 2001– 2010. Int J Tuberc Lung Dis. 2012;16(3):327–9. doi:10.5588/ ijtld.11.0251 pmid:22640445 11. Third antituberculosis drug resistance survey report (2016–2017). Ulaanbaatar: National Center for Communicable Diseases, Ministry of Health; 2017. 12. WHO consolidated guidelines on tuberculosis: module 4: treat- ment: drug-resistant tuberculosis treatment. Geneva: World Health Organization; 2020. Available from: https://apps.who.int/iris/han- dle/10665/332397, accessed 16 June 2022. 7. WHO consolidated guidelines on tuberculosis: module 2: screen- ing: systematic screening for tuberculosis disease. Geneva: World Health Organization; 2021. Available from: https://apps.who.int/ iris/handle/10665/340255, accessed 16 June 2022. 8. Dorjravdan M, Kouda K, Boldoo T, Dambaa N, Sovd T, Nakama C, et al. Association between household solid fuel use and tuberculo- sis: cross-sectional data from the Mongolian National Tuberculo- sis Prevalence Survey. Environ Health Prev Med. 2021;26(1):87. doi:10.1186/s12199-021-00996-4 pmid:34372757 9. Rapid communication on updated guidance on the management of tuberculosis in children and adolescents. Geneva: World Health Organization; 2021. Available from: https://apps.who.int/iris/han- dle/10665/344382, accessed 16 June 2022.