Epidemiological characteristics and trends of a Nationwide measles outbreak in Mongolia, 2015-2016

Impact of pneumococcal conjugate vaccine 13 introduction on severe lower respiratory tract infections associated with respiratory syncytial virus or influenza virus in hospitalized children in Ulaanbaatar, Mongolia

Objectives

Limited data indicate a beneficial effect of pneumococcal conjugate vaccines (PCVs) on respiratory syncytial virus (RSV) and influenza infections in young children. We evaluated the impact of 13-valent PCV (PCV13) introduction on the incidence of severe lower respiratory tract infections (LRTIs) associated with RSV or influenza in hospitalized children.

Methods

Our study was restricted to children aged <2 years with arterial oxygen saturation <93% and children with radiologically confirmed pneumonia nested in a pneumonia surveillance project in four districts of Ulaanbaatar city, Mongolia. We tested nasopharyngeal swabs collected on admission for RSV and influenza using quantitative reverse transcription-polymerase chain reaction. The impact of PCV13 on the incidence of LRTI outcomes associated with RSV or with influenza for the period April 2015-March 2020 was estimated. Incidence rate ratios comparing pre- and post-vaccine periods were estimated for each outcome for each district using negative binomial models and for all districts combined with a mixed-effects negative binomial model. Adjusted models accounted for seasonality. Sensitivity analyses were conducted to assess the robustness of our findings.

Results

Among 5577 tested cases, the adjusted incidence rate ratios showed a trend toward a reduction in RSV-associated outcomes: all LRTIs (0.77, 95% confidence interval [CI] 0.44-1.36), severe LRTIs (0.88, 95% CI 0.48-1.62), very severe LRTIs (0.76, 95% CI 0.42-1.38), and radiologically confirmed pneumonia (0.66, 95% CI 0.32-1.38) but inconsistent trends in outcomes associated with influenza.

Conclusions

No significant reductions were observed in any outcomes associated with RSV and influenza after PCV introduction.

Respiratory Syncytial Virus and Influenza Infections in Children in Ulaanbaatar, Mongolia, 2015-2021

BACKGROUND

Data available for RSV and influenza infections among children < 2 years in Mongolia are limited. We present data from four districts of Ulaanbaatar from April 2015 to June 2021.

METHODS

This study was nested in an enhanced surveillance project evaluating pneumococcal conjugate vaccine (PCV13) impact on the incidence of hospitalized lower respiratory tract infections (LRTIs). Our study was restricted to children aged < 2 years with arterial O2 saturation < 93% and children with radiological pneumonia. Nasopharyngeal (NP) swabs collected at admission were tested for RSV and influenza using qRT-PCR. NP swabs of all patients with radiological pneumonia and of a subset of randomly selected NP swabs were tested for S. pneumoniae (S.p.) by qPCR and for serotypes by culture and DNA microarray.

RESULTS

Among 5705 patients, 2113 (37.0%) and 386 (6.8%) had RSV and influenza infections, respectively. Children aged 2-6 months had a higher percentage of very severe RSV infection compared to those older than 6 months (42.2% versus 31.4%, p-value Fisher's exact = 0.001). S.p. carriage was detected in 1073/2281 (47.0%) patients. Among S.p. carriage cases, 363/1073 (33.8%) had S.p. and RSV codetection, and 82/1073 (7.6%) had S.p. and influenza codetection. S.p. codetection with RSV/influenza was not associated with more severe LRTIs, compared to only RSV/influenza cases.

CONCLUSION

In Mongolia, RSV is an important pathogen causing more severe LRTI in children under 6 months of age. Codetection of RSV or influenza virus and S.p. was not associated with increased severity.

[Maintaining measles elimination status in Colombia during outbreak control, 2019Manutenção do status de eliminação do sarampo na Colômbia durante o controle de surtos, 2019]

Objective

Describe measles outbreaks caused by importation of multiple cases, and the corresponding control interventions.

Methods

Descriptive study of measles outbreaks caused by the importation of multiple cases to Colombia in 2018-2019. Case definitions, classification of source of infection, collection of biological specimens, searches for suspected cases, case identification, and contact tracing were employed. Vaccination records were obtained from vaccination cards or from the Colombian information system. Nationality was determined from records found in the public health surveillance system. The incident command system was used, and response teams and action plans were activated to control outbreaks.

Results

In March 2018, the first case of measles imported from Venezuela was confirmed. Measles incidence in 2018 was 0.2 cases per 100 000 population, and it was 0.3 per 100 000 in 2019. The case fatality rate in 2019 was 0.4%. A total of 214 cases were confirmed in the Venezuelan population (91% with no vaccination history); and 69 outbreaks with no epidemiological link were studied. The MVi/Hulu Langat.MYS/26.11[D8] lineage was identified. Endemic circulation was prevented through innovative interventions such as infection surveillance and control, immediate notification, prioritization of field visits, and transmission risk level criteria.

Conclusions

Colombia controlled measles outbreaks that resulted from imported cases, and it prevented endemic circulation, thereby maintaining certification of measles elimination in the country.

Epidemiology of measles in Angola: Results from routine surveillance from 2015 to 2021

Background

Measles, an acute infectious disease of extremely contagious viral aetiology, has been eliminated in some parts of the world. To the best of the authors' knowledge, this is the first study on the epidemiological pattern of the measles virus in Angola, and it was carried out through a review of 7 years of observational retrospective data from the national measles laboratory surveillance programme.

Methods

A retrospective study using national databases on the laboratory surveillance of measles was performed. Patients of all ages with suspected measles from all provinces of Angola were included. Serum samples were used to detect IgM-type measles-virus-specific antibodies by enzyme-linked immunosorbent assay.

Findings

In total, 3690 suspected measles samples were sent to the Instituto Nacional de Investigação em Saúde. There were 962 (26.1%) laboratory-confirmed cases, and the most affected age group was children aged 1-4 years. The highest incidence rate per 100,000 population was found in Benguela (17.9%), followed by Huambo (16.7%) and Cuanza Sul (13.6%). Of the study years, the incidence rate per 1,000,000 population was highest in 2020 (11.9%). The most common complication was diarrhoea (n=406, 42.2%). Of the confirmed cases, 209 (21.7%) were vaccinated, 633 (65.8%) were unvaccinated, and 120 (12.5%) had unknown vaccination status. For all study years, vaccination coverage was <70%.

Interpretation

Measles continues to be a serious problem in Angola, and more efforts are needed to increase measles surveillance and achieve a high percentage of vaccination coverage.

Patient delay and health system delay of patients with newly diagnosed pulmonary tuberculosis in Mongolia, 2016-2017

Although diagnosis and treatment of tuberculosis (TB) have been improved in many countries, delays in the diagnosis and treatment remain problematic in resource-limited countries. This study aimed to identify factors affecting delays in TB care in Mongolia. Data on TB cases registered from January 2016 to December 2017 were obtained from the national registry of TB at the Department of TB Surveillance and Research in National Center for Communicable Disease. The total number of TB cases registered in these two years was 8,166, including 3,267 cases of newly diagnosed pulmonary TB. Pulmonary TB cases (1,836 males and 1,431 females) were analyzed to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). Patient delays longer than the median (28 days) were significantly associated with patient age >32 years (aOR=1.31, 95%CI: 1.14-1.51), residence in areas other than Ulaanbaatar (aimags) (aOR=1.38, 95%CI: 1.20-1.59), and smear-negative (aOR=0.57, 95%CI: 0.47-0.69). Health system delays longer than the median (7 days) were significantly associated with patient age >32 years (aOR=1.16, 95%CI: 1.00-1.33), residence in aimags (aOR=0.82, 95%CI: 0.71-0.95), special facilities including a prison hospital (aOR=4.40, 95%CI: 2.42-7.83), registration in 2017 relative to 2016 (aOR=0.83, 95%CI: 0.71-0.95), and smear-negative (aOR=1.72, 95%CI: 1.42-2.07). Total delays longer than the median (45 days) were significantly associated with patient age >32 years (aOR=1.39, 95%CI: 1.21-1.60), residence in aimags (aOR=1.27, 95%CI: 1.11-1.47), and smear-negative (aOR=0.74, 95%CI: 0.62-0.90). To shorten the total delay, improvement of the access to medical facilities in aimags is necessary.

Estimation of the unvaccinated among those aged less than 25 years according to aimag and its association with incidence of measles outbreak 2015-2016 in Mongolia

Mongolia had an epidemic of measles in 2015-2016, even though more than 90% of the population have been vaccinated since 1997. This study aimed to examine the associations between unvaccinated proportion and measles incidence according to aimag. Mongolia has 21 provinces (aimag) with Ulaanbaatar as the capital city. Vaccination coverage between 1991 and 2014 and measles incidence according to aimag were obtained from the National Center for Communicable Diseases of Mongolia database. Accumulated unvaccinated proportion (AUP) among those aged 1 to 24 years in 2015 was estimated from the unvaccinated at the 1st dose of 1991 to 2014. From 1991 to 2014, unvaccinated proportion among those aged 1 to 24 years in the whole country has been reducing from 28.0% in 1991 to 1.8% in 2014. The AUP in 2015 varied from 2.7% (Selenge) to 21.8% (Govisumber). The incidence was remarkably higher in only two aimags with a large density of the unvaccinated aged 1 to 24 years (Ulaanbaatar and Darkhan-Uul) than in the other aimags. The incidence had no significant correlation with the AUP, although the correlation between the incidence and the density of unvaccinated aged 1 to 24 years was significant when the two aimags were included. In conclusion, the AUP between 2.7% and 21.8% had no correlation with the incidence according to aimags in Mongolia measles epidemic 2015-2016.

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.

Measles and rubella IgG seroprevalence in persons 6 month-35 years of age, Mongolia, 2016

BACKGROUND

In 2015-2016, Mongolia experienced an unexpected large measles outbreak affecting mostly young children and adults. After two nationwide vaccination campaigns, measles transmission declined. To determine if there were any remaining immunity gaps to measles or rubella in the population, a nationally representative serosurvey for measles and rubella antibodies was conducted after the outbreak was over.

METHODS

A nationwide, cross-sectional, stratified, three-stage cluster serosurvey was conducted in November-December 2016. A priori, four regional strata (Ulaanbaatar, Western, Central, and Gobi-Eastern) and five age strata (6 months-23 months, 2-7 years, 8-17 years, 18-30 years, and 31-35 years) were created. Households were visited, members interviewed, and blood specimens were collected from age-appropriate members. Blood specimens were tested for measles immunoglobulin G (IgG) and rubella IgG (Enzygnost® Anti-measles Virus/IgG and Anti-rubella Virus/IgG, Siemens, Healthcare Diagnostics Products, GmbH Marburg, Germany). Factors associated with seropositivity were evaluated.

RESULTS

Among 4598 persons aged 6 months to 35 years participating in the serosurvey, 94% were measles IgG positive and 95% were rubella IgG positive. Measles IgG seropositivity was associated with increasing age and higher education. Rubella IgG seropositivity was associated with increasing age, higher education, smaller household size, receipt of MMR in routine immunization, residence outside the Western Region, non-Muslim religious affiliation, and non-Kazakh ethnicity. Muslim Kazakhs living in Western Region had the lowest rubella seroprevalence of all survey participants.

CONCLUSIONS

Nationally, high immunity to both measles and rubella has been achieved among persons 1-35 years of age, which should be sufficient to eliminate both measles and rubella if future birth cohorts have ≥ 95% two dose vaccination coverage. Catch-up vaccination is needed to close immunity gaps found among some subpopulations, particularly Muslim Kazakhs living in Western Region.

Phylogenetic and Epidemiological Analysis of Measles Viruses in Shenzhen, China from January 2015 to July 2019

Background

Measles morbidity and mortality were significantly reduced after the measles vaccine was introduced in China in 1965. However, measles outbreaks easily occur in densely populated areas, especially where there is no universal vaccination. The outbreak that occurred in Shenzhen, the Chinese city with the largest internal immigration, provides a lesson in measles virus mutation and measles prevention. The present study is a phylogenetic analysis of measles viruses and comparison of clinical signs between individuals with and without vaccination.

Material/Methods

We performed phylogenetic analysis of the nucleoprotein (N) genes of measles virus from 129 measles patients in Shenzhen from January 2015 to July 2019. Phylogenetic trees were constructed using the neighbor-joining method.

Results

The phylogenetic analysis showed all viruses were classified into genotype H1. In addition, there is often a seasonal measles outbreak in July each year. The clinical data showed that patients who were unvaccinated were more likely to have coughing, chronic bronchitis, conjunctivitis, catarrh, Koplik spots, and diarrhea. Children of migrant workers and those living in mountainous and rural districts accounted for most measles cases.

Conclusions

Our results showed there was a seasonal measles outbreak in Shenzhen Children’s Hospital. All the measles virus from 129 measles patients were H1 viruses. The clinical signs also showed a difference between unvaccinated and vaccinated patients. Moreover, most of the unvaccinated patients came from migrant worker families. We suggest there is a need for increased health promotion and vaccination programs for migrant workers and people living in remote villages.