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.

Antibody responses to mRNA versus non-mRNA COVID vaccines among the Mongolian population.

Background: A nationwide vaccination program against coronavirus disease 2019 (COVID-19) was started in Mongolia 4 months after the first local transmission, which occurred in November 2020. Previous studies have reported that two doses of COVID-19 vaccine result in increased antibody against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A study was conducted in Mongolia 2 weeks after the second vaccine dose. In the present study, the serum levels of antibodies of individuals 6 months after natural SARS-CoV-2 infection were compared with those of individuals who had not been infected or had been infected but had received two doses of vaccine, including BNT162b2, ChAdOx1 n-CoV-19, Gam-COVID-Vac, and BBIBP-CorV, which were used for COVID-19 in Mongolia. Methods: Of the 450 participants in this study, 237 (52.66%) were female and 213 (47.33%) were male. Four hundred people with or without SARS-CoV-2 infection who received two doses of 4 different COVID-19 vaccine participated in the vaccine groups and vaccine plus SARS-CoV-2 infection groups (50 in each group) and 50 individuals previously infected with SARS-CoV-2 participated in the unvaccinated group. Total antibody against SARS-CoV-2 infection, anti-SARS-CoV-2 N and S protein human IgG, and antibody inhibiting RBD-ACE2 binding were tested. Results: In the BNT162b2 vaccine group, total antibody against SARS-CoV-2 remained constant until 6 months, while the other vaccine groups showed a significant decrease, as compared to the unvaccinated group. The level of anti-SARS-CoV-2 S-RBD protein IgG was significantly increased in the ChAdOx1 n-CoV-19, Gam-COVID-Vac, and BNT162b2 vaccines groups as compared to the unvaccinated group. Participants in the BNT162b2 vaccine group had higher ACE2 inhibition efficiency compared to the other vaccine groups as well as the unvaccinated group. Conclusions: The BNT162b2 vaccine showed the highest level of antibody against SARS-CoV-2, followed by the BBIBP-CorV, Gam-COVID-Vac, and ChAdOx1 n-CoV-19 vaccines. The level of antibodies was increased in people infected with SARS-CoV-2 after vaccination, as compared to uninfected but vaccinated individuals.

Increase in Infant Measles Deaths During a Nationwide Measles Outbreak-Mongolia, 2015-2016.

BACKGROUND: Surveillance data from a large measles outbreak in Mongolia suggested increased case fatality ratio (CFR) in the second of 2 waves. To confirm the increase in CFR and identify risk factors for measles death, we enhanced mortality ascertainment and conducted a case-control study among infants hospitalized for measles. METHODS: We linked national vital records with surveillance data of clinically or laboratory-confirmed infant (aged <12 months) measles cases with rash onset during March-September 2015 (wave 1) and October 2015-June 2016 (wave 2). We abstracted medical charts of 95 fatal cases and 273 nonfatal cases hospitalized for measles, matched by age and sex. We calculated adjusted matched odds ratios (amORs) and 95% confidence intervals (CIs) for risk factors. RESULTS: Infant measles deaths increased from 3 among 2224 cases (CFR: 0.13%) in wave 1 to 113 among 4884 cases (CFR: 2.31%) in wave 2 (P < .001). Inpatient admission, 7-21 days before measles rash onset, for pneumonia or influenza (amOR: 4.5; CI, 2.6-8.0), but not other diagnoses, was significantly associated with death. DISCUSSION: Measles infection among children hospitalized with respiratory infections likely increased deaths due to measles during wave 2. Preventing measles virus nosocomial transmission likely decreases measles mortality.

Risk Factors for Measles Virus Infection Among Adults During a Large Outbreak in Postelimination Era in Mongolia, 2015.

Background: In 2015, a large nationwide measles outbreak occurred in Mongolia, with very high incidence in the capital city of Ulaanbaatar and among young adults. Methods: We conducted an outbreak investigation including a matched case-control study of risk factors for laboratory-confirmed measles among young adults living in Ulaanbaatar. Young adults with laboratory-confirmed measles, living in the capital city of Ulaanbaatar, were matched with 2-3 neighborhood controls. Conditional logistic regression was used to estimate adjusted matched odds ratios (aMORs) for risk factors, with 95% confidence intervals. Results: During March 1-September 30, 2015, 20 077 suspected measles cases were reported; 14 010 cases were confirmed. Independent risk factors for measles included being unvaccinated (adjusted matched odds ratio [aMOR] 2.0, P < .01), being a high school graduate without college education (aMOR 2.6, P < .01), remaining in Ulaanbaatar during the outbreak (aMOR 2.5, P < .01), exposure to an inpatient healthcare facility (aMOR 4.5 P < .01), and being born outside of Ulaanbaatar (aMOR 1.8, P = .02). Conclusions: This large, nationwide outbreak shortly after verification of elimination had high incidence among young adults, particularly those born outside the national capital. In addition, findings indicated that nosocomial transmission within health facilities helped amplify the outbreak.

Evolving understanding of the epidemiology of HIV and prevention needs among men who have sex with men in Ulaanbaatar, Mongolia.

This study describes HIV and syphilis bio-behavioral survey conducted among 200 men who have sex with men (MSM) recruited via respondent-driven sampling (RDS) between January 4 and February 1, 2012 in Ulaanbaatar, Mongolia. Participants were administered a structured questionnaire and data were analyzed with RDS-network program in STATA. Of 196 participants who agreed to be tested for HIV and syphilis, 21 (10.7 %; weighted 7.5; 95 % CI: 4.9, 11.4) and 8 (4.1 %; weighted 3.4; 95 % CI: 1.7, 6.7) were positive for HIV and syphilis, respectively. Exposure to HIV prevention programs in the last 12 months was reported by 51.8 % (weighted 33.6; 95 % CI: 27.6, 40.1) of participants. This study found high HIV prevalence and limited uptake of HIV prevention services among MSM in Mongolia. Given the concentrated HIV epidemic among MSM in Mongolia, HIV prevention, treatment and care services should focus on MSM as the population group most affected by HIV.

HIV and sexually transmitted infection-related risks among female sex workers in Mongolia: second-generation surveillance survey, 2011-2012.

BACKGROUND: Surveillance studies among female sex workers (FSWs) in Mongolia have found no HIV but high rates of syphilis, ranging from 10.7% in 2002 to 20.8% in 2007. OBJECTIVES: To determine the current prevalence of HIV and syphilis among FSWs, and to identify syphilis risk factors. METHODS: 761 FSWs were recruited by time-location sampling between 2 January and 29 March 2012 in Ulaanbaatar city, Darkhan-Uul, Orkhon, Khuvsgul and Dornod provinces in Mongolia. Participants were administered an anonymous structured survey. Blood samples were tested for HIV and syphilis. Bivariate and multivariate logistic regression analyses were performed to identify factors associated with syphilis. RESULTS: The mean age of participants was 31 (median 30, interquartile range 24-38). HIV knowledge was modest: 41.3% correctly answered all questions. Consistent condom use with clients was reported by 49.1% of participants and exposure to HIV prevention programmes by 50.1%. Although no cases of HIV were found, syphilis prevalence was -27.8% (95% CI 24.3% to 31.7%). In multivariate analyses, variables associated with syphilis were younger age (age >30 years, OR=0.96, 95% CI 0.92 to 0.99) and occurrence of genital ulcer (OR=2.24, 95% CI 1.17 to 4.28). CONCLUSIONS: A syphilis epidemic continues to grow among FSWs in Mongolia. These women are at high risk of HIV transmission if introduced into their sexual networks. With the increase in migration of mining workers in Mongolia, introduction of HIV may be imminent. Efforts to intensify treatment and prevention programmes among FSWs are needed.