Seroprevalence of Chikungunya Virus in a Rural Community in Brazil

<div><p>Background</p><p>The emergence of the Chikungunya virus (CHIKV) is currently expanding. In 2015, 38,332 cases of Chikungunya were reported to the Brazilian epidemiological surveillance system. Eighteen months after notification of the first case in the city of Feira de Santana, we conducted the first serosurvey to define the magnitude of transmission in a rural community in Brazil.</p><p>Methodology/Main findings</p><p>The serosurvey was conducted in a random sample of 450 residences in the Chapada district, located 100 kilometers from Feira de Santana. We administered questionnaires and tested 120 sera from Chapada district residents for CHIKV IgM- and IgG-specific antibodies. An individual with CHIKV infection was defined as any person with CHIKV IgM or IgG antibodies detected in the serum. One Hundred cases of Chikungunya were reported after prolonged rainfall, which reinforced the relationship between the rainfall index and CHIKV transmission. Eighteen months after the start of the outbreak, we identified a seroprevalence of 20% (95% CI, 15.4–35%). CHIKV IgG- and IgM-specific antibodies were detected in 22/120 (18.3%) and 6/120 (5.0%) individuals, respectively. Among seropositive patients, 13/24 (54.2%) reported fever and joint pain over the previous two years (p<0.01). The rate of symptomatic CHIKV infection was 40.7%.</p><p>Conclusions/Significance</p><p>We identified a moderate seroprevalence of Chikungunya in the Chapada district, and in half of the confirmed CHIKV infections, patients reported arthralgia and fever over the previous two years.</p></div

Numbers of CHIKV cases, anti-CHIKV IgM status and monthly precipitation in the Chapada district between October 2014 and November 2015.

<p>Numbers of CHIKV cases, anti-CHIKV IgM status and monthly precipitation in the Chapada district between October 2014 and November 2015.</p

Flow chart of the study enrollment and CHIKV IgM and IgG antibody positivity rates.

<p>Flow chart of the study enrollment and CHIKV IgM and IgG antibody positivity rates.</p

Seroprevalence of IgM and IgG antibodies against CHIKV in Chapada, April 2016 (N = 120).

<p>Seroprevalence of IgM and IgG antibodies against CHIKV in Chapada, April 2016 (N = 120).</p

Comparison of individuals with CHIKV IgG- and/or IgM-positive and negative antibodies in the Chapada district (N = 120).

<p>Comparison of individuals with CHIKV IgG- and/or IgM-positive and negative antibodies in the Chapada district (N = 120).</p

Description of 120 individuals enrolled in the serosurvey in the Chapada district.

<p>Description of 120 individuals enrolled in the serosurvey in the Chapada district.</p

Increased interregional virus exchange and nucleotide diversity outline the expansion of chikungunya virus in Brazil

Abstract The emergence and reemergence of mosquito-borne diseases in Brazil such as yellow fever, zika, chikungunya, and dengue have had serious impacts on public health. Concerns have been raised due to the rapid dissemination of the chikungunya virus across the country since its first detection in 2014 in Northeast Brazil. In this work, we carried out on-site training activities in genomic surveillance in partnership with the National Network of Public Health Laboratories that have led to the generation of 422 chikungunya virus genomes from 12 Brazilian states over the past two years (2021–2022), a period that has seen more than 312 thousand chikungunya fever cases reported in the country. These genomes increased the amount of available data and allowed a more comprehensive characterization of the dispersal dynamics of the chikungunya virus East-Central-South-African lineage in Brazil. Tree branching patterns revealed the emergence and expansion of two distinct subclades. Phylogeographic analysis indicated that the northeast region has been the leading hub of virus spread towards other regions. Increased frequency of C > T transitions among the new genomes suggested that host restriction factors from the immune system such as ADAR and AID/APOBEC deaminases might be driving the genetic diversity of the chikungunya virus in Brazil