 Influenza or “the flu” is an illness caused by seasonal influenza viruses which circulate in all parts of the world.  Seasonal influenza viruses circulate worldwide and can affect people in any age group.  In temperate climates, seasonal epidemics occur mainly during winter while in tropical regions, influenza seasonality is less obvious, and epidemics can occur throughout the year.  In Myanmar, June to September is the usual influenza season coinciding with the monsoon.

季節性インフルエンザ(Seasonal Influenza)の総括

Introduction 
Influenza morbidity and mortality are significant in the countries of South America, yet influenza vaccination is as low as 56.7% among pregnant women, reaching 76.7% of adults with chronic diseases. This article measures the relative values for the vaccination hesitancy indicators of confidence, complacency and convenience by risk-groups in urban areas of five countries of South America with contrasting vaccination rates, analyzing their association with sociodemographic variables and self-reported immunization status.


Methods 
An exit survey was applied to 640 individuals per country in Brazil, Chile, Paraguay, Peru and Uruguay, distributed equally across risk groups of older adults, adults with risk factors, children ≤6 and pregnant women. Indicators were constructed for vaccine confidence, complacency and convenience. Analysis of variance and multiple logistic analysis was undertaken.


Results 
Adults with risk factors are somewhat more confident of the influenza vaccine yet also more complacent. Convenience is higher for mothers of minors. Children and older adults report higher levels of vaccination. The 3Cs are more different across countries than across risk groups, with values for Chile higher for confidence and those for Uruguay the lowest. Complacency is lower in Brazil and higher in Uruguay. Results suggest that confidence and complacency affect vaccination rates across risk groups and countries.


Conclusions 
Influenza vaccine confidence, complacency and convenience have to be bolstered to improve effective coverage across all risk groups in the urban areas of the countries studied. The role played by country contextual and national vaccination programs has to be further researched in relation to effective coverage of influenza vaccine.

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Influenza vaccination hesitancy in five countries of South America. Confidence, complacency and convenience as determinants of immunization rates.

Viruses play a primary role as etiological agents of pandemics worldwide. Although there has been progress in identifying the molecular features of both viruses and hosts, the extent of the impact these and other factors have that contribute to interspecies transmission and their relationship with the emergence of diseases are poorly understood. The objective of this review was to analyze the factors related to the characteristics inherent to RNA viruses accountable for pandemics in the last 20 years which facilitate infection, promote interspecies jump, and assist in the generation of zoonotic infections with pandemic potential. The search resulted in 48 research articles that met the inclusion criteria. Changes adopted by RNA viruses are influenced by environmental and host-related factors, which define their ability to adapt. Population density, host distribution, migration patterns, and the loss of natural habitats, among others, have been associated as factors in the virus-host interaction. This review also included a critical analysis of the Latin American context, considering its diverse and unique social, cultural, and biodiversity characteristics. The scarcity of scientific information is striking, thus, a call to local institutions and governments to invest more resources and efforts to the study of these factors in the region is key.

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Key Factors That Enable the Pandemic Potential of RNA Viruses and Inter-Species Transmission: A Systematic Review.

Influenza B viruses (IBV) are an important cause of morbidity and mortality during interpandemic periods in the human population. Two phylogenetically distinct IBV lineages, B/Yamagata and B/Victoria, co-circulate worldwide and they present challenges for vaccine strain selection. Until the present study, there was little information regarding the pattern of the circulating strains of IBV in Uruguay. A subset of positive influenza B samples from influenza-like illness (ILI) outpatients and severe acute respiratory illness (SARI) inpatients detected in sentinel hospitals in Uruguay during 2012-2019 were selected. The sequencing of the hemagglutinin (HA) and neuraminidase (NA) genes showed substitutions at the amino acid level. Phylogenetic analysis reveals the co-circulation of both lineages in almost all seasonal epidemics in Uruguay, and allows recognizing a lineage-level vaccine mismatch in approximately one-third of the seasons studied. The epidemiological results show that the proportion of IBV found in ILI was significantly higher than the observed in SARI cases across different groups of age (9.7% ILI, 3.2% SARI) and patients between 5-14 years constituted the majority (33%) of all influenza B infection (p 25 years were particularly vulnerable to Yamagata lineage infections.

Epidemiology and Genetic Variability of Circulating Influenza B Viruses in Uruguay, 2012-2019.

Each year in Latin America and the Caribbean, seasonal influenza is associated with an estimated 36,500 respiratory deaths and 400,000 hospitalizations. Since the 2009 influenza A(H1N1) pandemic, the Region has made significant advances in the prevention and control of seasonal influenza, including improved surveillance systems, burden estimates, and vaccination of at-risk groups. The Global Influenza Strategy 2019-2030 provides a framework to strengthen these advances. Against the backdrop of this new framework, the University of Colorado convened in October 2020 its Immunization Advisory Group of Experts to review and discuss current surveillance, prevention, and control strategies for seasonal influenza in Latin America and the Caribbean, also in the context of the COVID-19 pandemic. This review identified five areas for action and made recommendations specific to each area. The Region should continue its efforts to strengthen surveillance and impact evaluations. Existing data on disease burden, seasonality patterns, and vaccination effectiveness should be used to inform decision-making at the country level as well as advocacy efforts for programmatic resources. Regional and country strategic plans should be prepared and include specific targets for 2030. Existing investments in influenza prevention and control, including for immunization programs, should be optimized. Finally, regional partnerships, such as the regional networks for syndromic surveillance and vaccine effectiveness evaluation (SARInet and REVELAC-i), should continue to play a critical role in continuous learning and standardization by sharing experiences and best practices among countries.

Seasonal Influenza Prevention and Control Progress in Latin America and the Caribbean in the Context of the Global Influenza Strategy and the COVID-19 Pandemic.

Objective 
There are limited published data about the circulation of influenza B/Victoria and B/Yamagata in Latin America and the Caribbean (LAC) and most countries have a vaccine policy that includes the use of the trivalent influenza vaccine. We analyzed influenza surveillance data to inform decision-making in LAC about prevention strategies, such as the use of the quadrivalent influenza vaccine.


Methods 
There are a total of 28 reference laboratories and National Influenza Centers in LAC that conduct influenza virologic surveillance according to global standards, and on a weekly basis upload their surveillance data to the open-access World Health Organization (WHO) platform FluNet. These data include the number of specimens tested for influenza and the number of specimens positive for influenza by type, subtype and lineage, all by the epidemiologic week of specimen collection. We invited these laboratories to provide additional epidemiologic data about the hospitalized influenza B cases. We conducted descriptive analyses of patterns of influenza circulation and characteristics of hospitalized cases. We compared the predominant B lineage each season to the lineage in the vaccine applied, to determine vaccine mismatch. A Chi-square and Wilcoxan statistic were used to assess the statistical significance of differences in proportions and medians at the P<0.05 level.


Findings 
During 2010–2017, the annual number of influenza B cases in LAC was ~4500 to 7000 cases. Since 2011, among the LAC-laboratories reporting influenza B lineage using molecular methods, both B/Victoria and B/Yamagata were detected annually. Among the hospitalized influenza B cases, there were statistically significant differences observed between B/Victoria and B/Yamagata cases when comparing age and the proportion with underlying co-morbid conditions and with history of oseltamivir treatment (P<0.001). The proportion deceased among B/Victoria and B/Yamagata hospitalized cases did not differ significantly. When comparing the predominant influenza B lineage detected, as part of surveillance activities during 63 seasons among 19 countries, to the lineage of the influenza B virus included in the trivalent influenza vaccine used during that season, there was a vaccine mismatch noted during 32% of the seasons analyzed.


Conclusions 
Influenza B is important in LAC with both B/Victoria and B/Yamagata circulating annually in all sub regions. During approximately one-third of the seasons, an influenza B vaccine mismatch was identified. Further analyses are needed to better characterize the medical and economic burden of each influenza B lineage, to examine the potential cross-protection of one vaccine lineage against the other circulating virus lineage, and to determine the potential impact and cost-effectiveness of using the quadrivalent vaccine rather than the trivalent influenza vaccine.

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Maribel Huaringa

Papers

Patterns of influenza B circulation in Latin America and the Caribbean, 2010-2017.