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Current SARS-CoV-2 containment measures rely on controlling viral transmission. Effective prioritization can be determined by understanding SARS-CoV-2 transmission dynamics. We conducted a systematic review and meta-analyses of the secondary attack rate (SAR) in household and healthcare settings. We also examined whether household transmission differed by symptom status of index case, adult and children, and relationship to index case. We searched PubMed, medRxiv, and bioRxiv databases between January 1 and July 25, 2020. High-quality studies presenting original data for calculating point estimates and 95% confidence intervals (CI) were included. Random effects models were constructed to pool SAR in household and healthcare settings. Publication bias was assessed by funnel plots and Egger's meta-regression test. 43 studies met the inclusion criteria for household SAR, 18 for healthcare SAR, and 17 for other settings. The pooled household SAR was 18.1% (95% CI: 15.7%, 20.6%), with significant heterogeneity across studies ranging from 3.9% to 54.9%. SAR of symptomatic index cases was higher than asymptomatic cases (RR: 3.23; 95% CI: 1.46, 7.14). Adults showed higher susceptibility to infection than children (RR: 1.71; 95% CI: 1.35, 2.17). Spouses of index cases were more likely to be infected compared to other household contacts (RR: 2.39; 95% CI: 1.79, 3.19). In healthcare settings, SAR was estimated at 0.7% (95% CI: 0.4%, 1.0%). While aggressive contact tracing strategies may be appropriate early in an outbreak, as it progresses, measures should transition to account for setting-specific transmission risk. Quarantine may need to cover entire communities while tracing shifts to identifying transmission hotspots and vulnerable populations. Where possible, confirmed cases should be isolated away from the household.

Mongolia experienced a nationwide measles outbreak during 1 March 2015–31 December 2016, with 49,077 cases reported to the WHO; many were among vaccinated young adults, suggesting a possible role of vaccine failure. Advanced laboratory methods, coupled with detailed epidemiological investigations, can help classify cases as vaccine failure, failure to vaccinate, or both. In this report, we conducted a study of cases to identify risk factors for breakthrough infection for a subset of laboratory-confirmed measles cases. Of the 193 cases analyzed, only 19 (9.8%) reported measles vaccination history, and 170 (88%) were uncertain. Measles-specific IgG avidity testing classified 120 (62%) cases as low IgG avidity, indicating no prior exposure to measles. Ten of these cases with low IgG avidity had a history of measles vaccination, indicating primary vaccine failure. Overall, sixty cases (31%) had high IgG avidity, indicating breakthrough infection after prior exposure to measles antigen through vaccination or natural infection, but the IgG avidity results were highly age-dependent. This study found that among young children aged 9 months–5 years, breakthrough infection was rare (4/82, 5%); however, among young adults aged 15–25 years, breakthrough infection due to secondary vaccine failure (SVF) occurred on a large scale during this outbreak, accounting for the majority of cases (42/69 cases, 61%). The study found that large-scale secondary vaccine failure occurred in Mongolia, which highlights the potential for sustained outbreaks in post-elimination settings due to “hidden” cohorts of young adults who may have experienced waning immunity. This phenomenon may have implications for the sustainability of measles elimination in countries that remain vulnerable to the importation of the virus from areas where it is still endemic. Until global measles elimination is achieved, enhanced surveillance and preparedness for future outbreaks in post- or peri-elimination countries may be required.

Hepatitis B vaccine (HepB), which has been available since 1982, provides lifelong protection against hepatitis B virus (HBV) infection and the associated 20%-30% increased lifetime risk for developing cirrhosis or hepatocellular carcinoma among >95% of vaccine recipients (1). Before HepB introduction into national childhood immunization schedules, the estimated hepatitis B surface antigen (HBsAg) prevalence in the World Health Organization (WHO) Western Pacific Region (WPR)* was >8% in 1990 (2). In 2005, the WPR was the first WHO region to establish a hepatitis B control goal, with an initial target of reducing HBsAg prevalence to <2% among children aged 5 years by 2012. In 2013, the WPR set more stringent control targets to achieve by 2017, including reducing HBsAg prevalence to <1% in children aged 5 years and increasing national coverage with both timely HepB birth dose (HepB-BD) (defined as administration within 24 hours of birth) and the third HepB dose (HepB3) to ≥95% (3). All WPR countries/areas endorsed the Regional Action Plan for Viral Hepatitis in the Western Pacific Region 2016-2020 in 2015 (4) and the Regional Framework for the Triple Elimination of Mother-to-Child Transmission of human immunodeficiency virus (HIV), Hepatitis B and Syphilis in Asia and the Pacific 2018-2030 (triple elimination framework) in 2017 (5). These regional targets and strategies are aligned with program targets established by the WHO Global Health Sector Strategy on Viral Hepatitis 2016-2021 that aim to reduce HBsAg prevalence among children aged 5 years to ≤1% by 2020 and to ≤0.1% by 2030 (6). This report describes progress made to achieve hepatitis B control in the WPR and the steps taken to eliminate mother-to-child transmission (MTCT) of HBV during 2005-2017. During this period, regional timely HepB-BD and HepB3 coverage increased from 63% to 85% and from 76% to 93%, respectively. As of December 2017, 15 (42%) countries/areas achieved ≥95% timely HepB-BD coverage; 18 (50%) reached ≥95% HepB3 coverage; and 19 (53%) countries/areas as well as the region as a whole were verified to have achieved the regional and global target of <1% HBsAg prevalence among children aged 5 years. Continued implementation of proven vaccination strategies will be needed to make further progress toward WPR hepatitis B control targets. In addition to high HepB-BD and HepB3 coverage, enhanced implementation of complementary hepatitis B prevention services through the triple elimination framework, including routine HBsAg testing of pregnant women, timely administration of hepatitis B immunoglobulin to exposed newborns, and antiviral treatment of mothers with high viral loads, will be needed to achieve the global hepatitis B elimination target by 2030.

Reef et al summarizes progress toward rubella elimination and congenital rubella syndrome (CRS) prevention in WPR during 2000-2019. Coverage with a first dose of rubella-containing vaccine (RCV1) increased from 11% in 2000 to 96% in 2019. During 1970-2019, approximately 84 million persons were vaccinated through 62 supplementary immunization activities (SIAs) conducted in 27 countries. Reported rubella incidence increased from 35.5 to 71.3 cases per million population among reporting countries during 2000-2008, decreased to 2.1 in 2017, and then increased to 18.4 in 2019 as a result of outbreaks in China and Japan.

Mongolia experienced a large, nationwide, measles outbreak with very high incidence among young adults, despite high historical immunization coverage. A case-control outbreak investigation found that measles risk among adults was associated with hospital exposure and birth outside the capital city. Abstract 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.

Background/Objectives: The aim was to assess whether a machine learning (ML) algorithm could empower the ability of ultrasound (US) integrated with shear-wave elastography (SWE) to preoperatively define the ALN status in breast cancer (BC). Methods: Patients with at least one histologically proven BC lesion, who underwent preoperative breast US and SWE were retrospectively enrolled. BC lesions were segmented on US and SWE images by three different operators and radiomics features were extracted. A multi-step US and SWE feature selection was performed. A Simple Logistic ML classifier was applied to the dataset to predict the ALN status, its performance assessed through the AUC and Matthews Correlation Coefficient (MCC). The performance of the ML classifier was compared to that of an expert radiologist, who evaluated the US B-mode lymph-node features included in the test set. Results: A total of 133 BC lesions were included and divided into a training set, composed of 89 BC lesions (ALN−: 52; ALN+: 37), and a test set, including 44 BC lesions (ALN−: 24; ALN+: 20). Eight features out of the 1098 radiomics features extracted from US and SWE images were selected to build the predictive model. Simple Logistic classifier showed AUC of 0.685 and 0.677, MCC of 0.387 and 0.375 in the training and test set, respectively. The performance of the expert radiologist was higher than that of the ML classifier (AUC = 0.817), but not significantly different (p = 0.481). Conclusions: The inclusion of SWE-derived radiomics features could aid in the preoperative assessment of ALN status in BC using an ML approach.

The emergence of Zika virus has challenged outbreak surveillance systems in many at-risk, low-resource countries. As the virus has been linked with Guillain-Barré syndrome, routine data on the incidence of acute flaccid paralysis (AFP) may provide a useful early warning system for the emergence of Zika virus. We documented all Zika virus outbreaks and cases in 21 Pacific Islands and territories for the years 2007 to 2015. We extracted data from the Global Polio Eradication Initiative database on the reported and expected annual incidence of AFP in children younger than 15 years. Using a Poisson probability test, we tested the significance of unexpected increases in AFP in years correlating with Zika virus emergence. Data were analysed separately for each Pacific Island country and territory. In most Pacific Island countries, early warning surveillance for acute public health threats such as Zika virus is hampered by poor health infrastructure, insufficient human resources and geographical isolation. Only one example was found (Solomon Islands in 2015) of a significant increase in reported AFP cases correlating with Zika virus emergence. We found no conclusive evidence that routinely reported AFP incidence data in children were useful for detecting emergence of Zika virus in this setting. More evidence may be needed from adult populations, who are more likely to be affected by Guillain-Barré syndrome. Reporting of AFP may be deficient in regions certified as polio-free.

The emergence of Zika virus has challenged outbreak surveillance systems in many at-risk, low-resource countries. As the virus has been linked with Guillain-Barre syndrome, routine data on the incidence of acute flaccid paralysis (AFP) may provide a useful early warning system for the emergence of Zika virus. We documented all Zika virus outbreaks and cases in 21 Pacific Islands and territories for the years 2007 to 2015. We extracted data from the Global Polio Eradication Initiative database on the reported and expected annual incidence of AFP in children younger than 15 years. Using a Poisson probability test, we tested the significance of unexpected increases in AFP in years correlating with Zika virus emergence. Data were analysed separately for each Pacific Island country and territory. In most Pacific Island countries, early warning surveillance for acute public health threats such as Zika virus is hampered by poor health infrastructure, insufficient human resources and geographical isolation. Only one example was found (Solomon Islands in 2015) of a significant increase in reported AFP cases correlating with Zika virus emergence. We found no conclusive evidence that routinely reported AFP incidence data in children were useful for detecting emergence of Zika virus in this setting. More evidence may be needed from adult populations, who are more likely to be affected by Guillain-Barre syndrome. Reporting of AFP may be deficient in regions certified as polio-free./L'emergence du virus Zika pose un probleme pour les systemes de surveillance des epidemies dans de nombreux pays a faibles ressources et a risque. Etant donne qu'un lien a ete etabli entre ce virus et le syndrome de Guillain-Barre, les donnees systematiquement collectees sur l'incidence de la paralysie flasque aiguee (PFA) pourraient peut-etre aider a etablir un systeme d'alerte anticipee pour l'emergence du virus Zika. Nous avons documente toutes les flambees de virus Zika et tous les cas d'infection a virus Zika dans 21 iles et territoires du Pacifique, sur la periode 2007 a 2015. A partir de la base de donnees de l'Initiative mondiale pour l'eradication de la poliomyelite, nous avons extrait des donnees sur l'incidence annuelle signalee et l'incidence annuelle prevue de la PFA chez les enfants de moins de 15 ans. En utilisant un test de probabilite de Poisson, nous avons teste la significativite de la correlation entre les augmentations annuelles imprevues des cas de PFA et l'emergence du virus Zika. Les donnees ont ete analysees separement pour chaque territoire et chaque ile du Pacifique. Dans la plupart des iles du Pacifique, les activites de surveillance et d'alerte anticipee des menaces aiguees de sante publique (telles que celle representee par le virus Zika) sont rendues difficiles par les deficiences des infrastructures de sante, l'insuffisance des ressources humaines et l'isolement geographique des populations. Nous n'avons constate qu'un seul exemple (Iles Salomon, 2015) d'une augmentation significative des cas signales de PFA coincidant avec une emergence du virus Zika. Nous n'avons trouve aucune preuve concluante permettant d'affirmer que les donnees systematiquement signalees sur l'incidence de la PFA chez les enfants ont ete utiles, dans ces contextes, pour detecter une emergence du virus Zika. Des donnees complementaires pourraient etre necessaires en lien avec les populations adultes, qui sont plus susceptibles d'etre affectees par le syndrome de Guillain-Barre. Il est egalement possible que le signalement des PFA soit defaillant dans ces regions certifiees exemptes de poliomyelite./La aparicion del virus de Zika ha puesto en peligro los sistemas de control del brote en muchos paises en riesgo con escasos recursos. Dado que el virus se ha relacionado con el sindrome de Guillain-Barre, los datos rutinarios sobre la incidencia de paralisis flacida aguda (PFA) pueden proporcionar un sistema de advertencia temprana util para la aparicion del virus de Zika. Se documentaron todos los brotes y casos del virus de Zika en 21 islas y territorios del Pacifico entre los anos 2007 y 2015. Se recopilo informacion de la base de datos de la Iniciativa de Erradicacion Mundial de la Poliomielitis sobre la incidencia anual de PFA informada y prevista en ninos menores de 15 anos. Utilizando una prueba de probabilidad de Poisson, se demostro la importancia de los aumentos inesperados de PFA en los anos correlacionados con la aparicion del virus de Zika. Se analizaron los datos por separado por cada pais y territorio de las Islas del Pacifico. En la mayoria de los paises de las Islas del Pacifico, el control de aviso temprano para amenazas sanitarias publicas agudas como el virus de Zika se ve obstaculizado por una infraestructura sanitaria pobre, escasos recursos humanos y aislamiento geografico. Unicamente se encontro un ejemplo (Islas Salomon en 2015) de un gran aumento en los casos de PFA informada que se correlacionaron con la aparicion del virus de Zika. No se encontraron pruebas...

Approach We documented all Zika virus outbreaks and cases in 21 Pacific Islands and territories for the years 2007 to 2015. We extracted data from the Global Polio Eradication Initiative database on the reported and expected annual incidence of AFP in children younger than 15 years. Using a Poisson probability test, we tested the significance of unexpected increases in AFP in years correlating with Zika virus emergence. Data were analysed separately for each Pacific Island country and territory. Approche Nous avons documente toutes les flambees de virus Zika et tous les cas d'infection a virus Zika dans 21 iles et territoires du Pacifique, sur la periode 2007 a 2015. A partir de la base de donnees de l'Initiative mondiale pour l'eradication de la poliomyelite, nous avons extrait des donnees sur l'incidence annuelle signalee et l'incidence annuelle prevue de la PFA chez les enfants de moins de 15 ans. En utilisant un test de probabilite de Poisson, nous avons teste la significativite de la correlation entre les augmentations annuelles Imprevues des cas de PFA et l'emergence du virus Zika. Les donnees ont ete analysees separement pour chaque territoire et chaque ile du Pacifique.

In 2005, the Regional Committee for the World Health Organization (WHO) Western Pacific Region (WPR)* established a goal for measles elimination by 2012 (1). To achieve this goal, the 37 WPR countries and areas implemented the recommended strategies in the WPR Plan of Action for Measles Elimination (2) and the Field Guidelines for Measles Elimination (3). The strategies include 1) achieving and maintaining ≥95% coverage with 2 doses of measles-containing vaccine (MCV) through routine immunization services and supplementary immunization activities (SIAs), when required; 2) conducting high-quality case-based measles surveillance, including timely and accurate testing of specimens to confirm or discard suspected cases and detect measles virus for genotyping and molecular analysis; and 3) establishing and maintaining measles outbreak preparedness to ensure rapid response and appropriate case management. This report updates the previous report (4) and describes progress toward measles elimination in WPR during 2013-2017. During 2013-2016, estimated regional coverage with the first MCV dose (MCV1) decreased from 97% to 96%, and coverage with the routine second MCV dose (MCV2) increased from 91% to 93%. Eighteen (50%) countries achieved ≥95% MCV1 coverage in 2016. Seven (39%) of 18 nationwide SIAs during 2013-2017 reported achieving ≥95% administrative coverage. After a record low of 5.9 cases per million population in 2012, measles incidence increased during 2013-2016 to a high of 68.9 in 2014, because of outbreaks in the Philippines and Vietnam, as well as increased incidence in China, and then declined to 5.2 in 2017. To achieve measles elimination in WPR, additional measures are needed to strengthen immunization programs to achieve high population immunity, maintain high-quality surveillance for rapid case detection and confirmation, and ensure outbreak preparedness and prompt response to contain outbreaks.