Investigation of an outbreak of acute respiratory disease in an indigenous village in Brazil: Contribution of Influenza A(H1N1)pdm09 and human respiratory syncytial viruses

Abstract

Analyses of the 2009 H1N1 influenza pandemic and post-pandemic years showed high attack rates and severity among indigenous populations. This study presents the characteristics of the first documented influenza outbreak in indigenous peoples in Brazil, that occurred from 30th March to 14th April 2016 in a Guarani village in Southeast Region. Acute respiratory infections were prospectively investigated. The majority of the 73 cases were influenza-like illness (ILI) (63.0%) or severe acute respiratory infection (SARI) (20.5%). The ILI+SARI attack rate (35.9%) decreased with increasing age. There was a high influenza vaccination rate (86.3%), but no statistically significant difference in vaccination rates between severe and non-severe cases was seen (p = 0.334). Molecular analyses of 19.2% of the cases showed 100% positivity for influenza A(H1N1)pdm09 and/or hRSV. Influenza A(H1N1)pdm09 was included in the 6B.1 genetic group, a distinct cluster with 13 amino acid substitutions of A/California/07/2009-like. The hRSV were clustered in the BA-like genetic group. The early arrival of the influenza season overlapping usual hRSV season, the circulation of a drifted influenza virus not covered by vaccine and the high prevalence of risk factors for infection and severity in the village jointly can explain the high attack rate of ARI, even with a high rate of influenza vaccination. The results reinforce the importance of surveillance of respiratory viruses, timely vaccination and controlling risk factors for infection and severity of in the indigenous populations in order to preventing disease and related deaths, particularly in children.

Differential Disease Severity and Whole Genome Sequence Analysis for Human Influenza A/H1N1pdm Virus in 2015-2016 Influenza Season

“…Reports also showed H1N1pdm impacted the southern hemisphere in the 2016 season. In Sao Paulo State and a village in Brazil, an earlier influenza season with confirmed H1N1pdm 6B.1 as the dominant strain were reported [34, 35]. Reunion Island suffered the highest number of ICU hospitalization since 2009 and most were infected by H1N1pdm during April to August 2016 [36].…”

Covid-19 pandemic and the motivations for demanding health service in indigenous villages

“…Researches on outbreaks in indigenous villages during the H1N1 pandemic in different locations around the world in 2009 reinforce the importance of health education provided massively by health professionals in the villages for disease control (9)(10) . Studies on outbreaks and prevalence of respiratory syndromes in Brazil reiterate this aspect (4)(5)(6) .…”

“…However, for more effectiveness, this campaign could have integrated a broader health education program for the comprehensive promotion of children's health. The vaccination against H1N1 performed in the population of the Guarani ethnicity in southeastern Brazil, for example, was not sufficient to prevent the strong outbreak of flu syndrome in the region in 2016 (6) . Other measures to prevent this syndrome should have been implemented considering the lifestyle of this population.…”

“…The indigenous way of life, family organization, housing construction and type of occupation vary according to the tradition of each ethnicity and the degree of interaction with the surrounding society. In general, indigenous habits and rituals involve collective activities (6) . Indigenous people have less protection against certain etiological agents, which results in illness and/or death (5) .…”

“…Indigenous mortality was four times higher than mortality of the general Brazilian population during the H1N1 pandemic in 2019 (2) . Studies describe a high rate of attack in outbreaks of respiratory diseases among indigenous people (4)(5)(6) . This scenario shows the greater susceptibility of this population group to the attack of respiratory diseases, such as covid-19 (2) .…”