Molecular epidemiology of SARS-CoV-2 in Mongolia, first experience with nanopore sequencing in lower- and middle-income countries setting.

BACKGROUND: Coronavirus disease (COVID-19) has had a significant impact globally, and extensive genomic research has been conducted on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lineage patterns and its variants. Mongolia's effective response resulted in low prevalence until vaccinations became available. However, due to the lack of systematically collected data and absence of whole genome sequencing capabilities, we conducted a two-stepped, nationally representative molecular epidemiologic study of SARS-CoV-2 in Mongolia for 2020 and 2021. METHODS: We used retrospective analysis of stored biological samples from November 2020 to October 2021 and a variant-specific real-time reverse transcription polymerase chain reaction (RT-PCR) test to detect SARS-CoV-2 variants, followed by whole genome sequencing by Nanopore technology. Samples were retrieved from different sites and stored at -70°C deep freezer, and tests were performed on samples with cycle threshold <30. RESULTS: Out of 4879 nucleic acid tests, 799 whole genome sequencing had been carried out. Among the stored samples of earlier local transmission, we found the 20B (B.1.1.46) variant predominated in the earlier local transmission period. A slower introduction and circulation of alpha and delta variants were observed compared to global dynamics in 2020 and 2021. Beta or Gamma variants were not detected between November 2020 and September 2021 in Mongolia. CONCLUSIONS: SARS-CoV-2 variants of concerns including alpha and delta were delayed in circulation potentially due to public health stringencies in Mongolia. We are sharing our initial experience with whole genome sequencing of SARS-CoV-2 from Mongolia, where sequencing data is sparse.

Seroprevalence and risk factors of tick-borne encephalitis in Mongolia between 2016 and 2022.

The tick-borne encephalitis virus (TBEV) is a zoonotic agent that causes severe encephalitis in humans and is transmitted through the bites of infected ticks. Ixodes ticks are the primary vector for TBEV in Mongolia, and approximately 3.4% carry the TBEV. The ticks are capable of not only transmitting these viruses but also serve as excellent reservoir hosts. The Dermacenter tick species may have similar properties. TBEV is a significant cause of virus-related diseases of the central nervous system in many European countries as well as in China, Russia, and Mongolia. Our objectives were to investigate TBEV seroprevalence and infection risk factors in different biogeographical zones and provinces, especially in the highly endemic areas of Mongolia. Serum samples were collected from individuals who experienced tick bites (n = 993) in Mongolia between 2016 and 2022. Enzyme-linked immunosorbent assay of the samples was performed to evaluate for TBEV-specific immunoglobulin (Ig)M and IgG. We analyzed the risk factors and seroprevalence of TBEV infection among these individuals using a cross-sectional, questionnaire-based study. Statistical analyses were performed using a multistage cluster sampling survey design, and all data were analyzed using the R software. TBEV IgM and IgG antibodies were detected in 8.1% (80/993) and 20.2% (201/993) of all serum samples, respectively. The seroprevalence was significantly higher in men (68%, 95% confidence interval [CI]: 1.63-3.13, odds ratio [OR]: 2.25) than in women (p < 0.001). Additionally, the seroprevalence was significantly higher among unemployed (35.0%, 95% CI: 0.31-0.84, OR: 0.51) than employed individuals (p < 0.001). The seroprevalence was the highest among the 25-29 and 35-39-year age groups (11%, 95% CI: 1.29-5.51, OR: 2.65 and 11%, 95% CI: 0.94-3.87, OR: 1.9, respectively), and the lowest in the 65-69-year age group (4%, 95% CI: 0.46-6.15, OR: 1.83) (p < 0.001). Furthermore, the seroprevalence was the highest in Selenge province and the capital city Ulaanbaatar (40%, 95% CI: 1.73-21.7, OR: 5.07 and 28%, 95% CI: 0.51-6.89, OR: 1.57, respectively) and the lowest in Bayan-Ulgii and Dornod provinces (0.5%, 95% CI: 0.06-12.4, OR: 1.33 and 0.5%, 95% CI: 0.03-6.24, OR: 0.72, respectively). TBEV infection incidence remained low in most regions of Mongolia but increased in endemic areas. Furthermore, in the univariate subgroup analysis, age, occupation status, and residential area were significantly associated with TBEV seroprevalence.

Seroprevalence and risk factors of Borrelia burgdorferi sensu lato and Rickettsia species infection in humans in Mongolia, 2016-2020.

Borrelia burgdorferi sensu lato and Rickettsia spp. are worldwide causes of tick-borne infections. We aimed to estimate the seroprevalence of immunoglobulin G (IgG) antibodies against different tick-borne diseases (TBDs) and determine risk factors among Mongolians from 2016 to 2020. Blood samples were obtained from voluntary participants with a history of suspected tick bite who visited our hospital, and IgG antibodies against Rickettsia and Borrelia were detected using enzyme-linked immunosorbent assay (ELISA). The IgG antibody seropositivity rate against Rickettsia was 21.8% (1032/4724), while 3.4% (162/4724) of participants tested positive for serum IgG antibodies against Borrelia by ELISA.Binary logistic regression analysis was performed to evaluate risk factors for tick-borne rickettsiosis (TBR) and tick-borne borreliosis (TBB) using IgG serum sample. Age, occupation, and residence were significantly associated with these diseases; however, sex did not show any significant association. Seroprevalence was significantly higher among herders (40.6%, 95% confidence interval [CI]: 35.5-45.8; odds ratio [OR] 0.61; P < 0.001) and students (32.8%, 95% CI: 30.2-35.4; OR 0.75; P < 0.001) than among individuals with other occupations. The 25-29 age group had a slightly higher seroprevalence (35.1%, 95% CI: 28.1-42.6; OR 0.61; P < 0.006) than those in other age groups. Province was a stronger predictor of TBR than occupation and age group. In univariate subgroup analysis by age group, occupation, and residence were significantly associated with TBR seroprevalence, whereas age and province were associated with TBB seroprevalence. Thus, risk factors for TBD include residence, occupation, and age group. This study was conducted using samples from all Mongolian provinces and the capital city, and the risk factors and prevalence of Rickettsia and Borreliaare highlighted.

A case series of fatal meningoencephalitis in Mongolia: epidemiological and molecular characteristics of tick-borne encephalitis virus.

In Mongolia, the incidence and fatality rates of tick-borne encephalitis (TBE) have been increasing. We aimed to identify the epidemiological and molecular characteristics of tick-borne encephalitis virus (TBEV) associated with fatal meningoencephalitis in Mongolia. We conducted a descriptive study of 14 fatal cases of TBE that occurred between 2008 and 2017 in Mongolia. Reverse transcription polymerase chain reaction (RT-PCR) was used to detect viral RNA in brain tissue. RT-PCR products from six patients who died from TBE between 2013 and 2017 were directly sequenced and analysed phylogenetically. Ticks collected from Selenge and Bulgan provinces were also tested for TBEV by RT-PCR. Between 2008 and 2017, there were 14 fatal TBE cases in hospitals in Mongolia. The 14 patients who died reported receiving tick bites in Bulgan or Selenge province; 71.4% of deaths resulted from tick bites in Bulgan province. The TBE case fatality rate was 28.6% for patients in Bulgan province and 2.7% for those in Selenge province. All of the fatalities were men; the median age was 45 ± 12.6 years. Tick bites occurred between April and June in forested areas. In 2013, a 388 base pair fragment of the envelope (E) gene was obtained from a hospitalized patient. The closest relatives of this virus are Far-Eastern TBEV isolates. The case fatality rate differed between two provinces where tick bites occurred. A higher number of TBE cases and the virulent Far-Eastern subtype occurred in patients in Bulgan province. This province should increase vaccination coverage, training, education and investigations.

A path to cooperation between China and Mongolia towards the control of echinococcosis under the Belt and Road Initiative.

Health is the core of development. Health cooperation between countries plays a pivotal role under the Belt and Road Initiative (B&R). In 2013, China launched its B&R to improve the international cooperation of which health was an important component. As one of the neglected zoonotic diseases, echinococcosis has become a public health concern and is on top of the government agenda among neglected zoonosis in Mongolia. The transmission of the disease involves animal husbandry, and its characteristics determine the prevention and control of such diseases which requires cross-sector collaboration and comprehensive prevention and control strategies. Taking echinococcosis as an entry point and adopting a 'Mongolia-led, China-supported, and results-sharing' approach to public health cooperation will not only contribute to the advancement of Mongolia's national health coverage, but also promoting China's capacity to engage in global health. In this way, it contributes to meeting the sustainable development goals, especially goal 3, target 3.3: by 2030, end the epidemics of AIDS, tuberculosis, malaria and neglected tropical diseases and combat hepatitis, water-borne diseases and other communicable diseases. This paper provides an overview on how the cooperation between China and Mongolia under the context of B&R was initiated, planned and moved forward to implementation. The experience may provide a good model and inform policy and practice for other bilateral cooperations.