Brazil has reported more than 1,600 cases of hantavirus cardiopulmonary syndrome (HPS) since 1993, with a 39% rate of reported fatalities. Using a recombinant nucleocapsid protein of
Hantaviruses are emerging pathogens that have gained increasing attention in the last few decades [
As Manigold and Vial [
In Brazil the HPS cases are mostly caused by five genotypes of hantavirus:
The first confirmed cases of HPS in North America occurred in 1993, and six months later, it was reported in Brazil [
Serological methods are commonly used for hantavirus diagnosis, including enzyme-linked immunosorbent assays (ELISAs), immunofluorescence assays, and immunoblot assays. Additionally, hantavirus isolation in Vero E6 cell cultures and detection of anti-hantavirus antibodies by plaque reduction neutralization are also used for diagnosis. Nevertheless, both methods require labor-intensive, time-consuming, and biosafety-level-three conditions [
Here, in an effort to better understand and study the distribution of infections by hantavirus in Brazil, we present the results of a serological survey including individuals living in urban and rural areas near the Amazonian forest and in subtropical areas near rain forests that have degraded environmental conditions. Sera from the participants were tested via an IgG-ELISA [
The design for minimum sample size was performed in accordance with the calculations specified by Luiz and Magnanini [
Map of Brazil showing the four study sites: the city of Jacupiranga (RV) and Teodoro Sampaio (PP) in São Paulo state in the subtropical region and Machadinho do Oeste city and the Machado river region Rondônia state in the tropical region.
The enrollment of participants in this serological survey was authorized by the Ethics Committee of ICB/USP (670/2005), and the confidentiality of their personal information was ensured. Blood collection of the participants was only performed after signing the informed consent, in compliance with the rules of the ethics committee. After participants signed the consent form, the survey was applied for evaluation of the risk factors, gender, age, education, and another aspects as epidemiological information.
Sera were tested by an indirect IgG enzyme-linked immunosorbent assay (ELISA) using the N recombinant protein (recN) of ARAV as antigen, as described by Figueiredo et al. [
The recN protein used as the antigen and the positive/negative control samples were kindly provided by the Laboratories of Arboviruses and Rodent-borne Viruses of the University of São Paulo School of Medicine (Luis Tadeu M. Figueiredo, Ph.D., M.D.).
A statistical analysis of the results was performed with Prism version 5.0 (GraphPad Software). Associations of positive serological tests with subtropical areas and demographic and socioeconomic variables were analyzed using the Chi-square test, and
Sera from all 1,310 participants in this study were tested using the ARAV recN-ELISA, and 82 (6.2%) showed positive results. In the Machado river group (MR), 22 (1.6%) of the 435 participants examined had IgG antibodies to hantavirus. In the Machadinho do Oeste county, 40 (3.0%) among the 633 participants analyzed were previously infected by hantavirus. In Jacupiranga county (RV) in the southeastern part of Brazil, 14 (9.0%) of the 157 participants had IgG antibodies to hantavirus. In Teodoro Sampaio county (PP) in the São Paulo state, 6 (7.0%) of the 85 participants were seropositive for hantavirus, as shown in Figure
(a) demonstrated the absorbance values by ELISA for the total positive (POSIT) and negative (NEGAT) individuals from four different sites (Jacupiranga, SP, in Ribeira Valley, VR; Teodoro Sampaio/SP in Pontal Parapanema, PP; Machado River/RO, RM; and Machadinho do Oeste/RO) for the presence of anti-hantavirus IgG antibodies. (b) The graphic represent results from this four study sites in the tropical and subtropical region (Jacupiranga/SP in Ribeira Valley, VR; Teodoro Sampaio/SP in Pontal Parapanema, PP; Machado River/RO, RM; and Machadinho do Oeste/RO), categorized by gender. (c) The graphics represent results from this four study sites in the tropical and subtropical region (Jacupiranga/SP in Ribeira Valley, VR; Teodoro Sampaio/SP in Pontal Parapanema, PP; Machado River/RO, RM; and Machadinho do Oeste/RO) categorized by age (groups of 20 years).
Participants from Jacupiranga and Teodoro Sampaio counties in the subtropical southeastern region of Brazil were significantly (
Among the hantavirus seropositive, 60.9% were female participants, as shown in Figure
The ages of those seropositive to hantavirus ranged from five to 82 years but included mostly young adults greater than 20 years of age, as shown in Figure
The seropositivity to hantavirus was not correlated with education level, place of birth, time of residence in the study site, or other risk factors evaluated for epidemiological analyses.
In this study, we evaluated the hantavirus seroprevalence in people living in areas presumed of high risk for this infection. A high proportion of hantavirus seropositive subjects were observed in participants from Jacupiranga county (9%) and Teodoro Sampaio (7%), both of which located at subtropical regions of the state of São Paulo. This value is significantly higher than the 1.6% of seropositive cases reported in a serological survey in the Ribeira Valley performed in 1993 [
The seroprevalence of 6% and 8% to hantavirus observed in the present study is not outside standards range observed in the literature, like, for example, the rate of 14% observed in the population of Jardinopolis county in the state of Sao Paulo [
In the tropical Amazonian region of Rondônia, the seroprevalence to hantavirus in Machadinho do Oeste county (3%) and Machado river region (2.8%) was similar. Other studies conducted in the Amazon region have yielded different hantavirus seroprevalence rates. A survey of several cities in the Amazonas state between 2007 and 2009 yielded a seroprevalence rate of 0.6% [
According description by Nava et al. [
A significantly higher proportion of seropositive individuals to hantavirus was observed in the subtropical region of Brazil (São Paulo state) compared to the tropical region (Rondônia state). It is possible that the higher occurrence of hantavirus infections in São Paulo state is associated with the degradation of the local environment. São Paulo, which is the most densely populated state in Brazil, has two main ecosystems: the “cerrado (savannah)” in its western region and neotropical Atlantic Rain Forests along the coast. These ecosystems sustain Sigmodontinae rodents and have been modified, segmented, and damaged by extensive sugarcane, soybean and coffee farming, livestock raising, and rapid and poorly planned urbanization. Such degraded landscapes allow close contact of humans with zoonoses, resulting in enhanced transmission of pathogens to humans. Environmental degradation favors the abundance of opportunistic rodent species (
One of the limitations of this study is the seroprevalence accuracy of data available at these areas combined with full background from participants of this study. Also, it was impossible to analyze hantavirus infection in rodents from the same studied sites since we did not collect samples. Probably, a comparison of seropositivity to hantavirus among humans and rodents at the different study sites would help to understand why more infections occur in the subtropical area of Brazil (São Paulo state) more than in the tropical area (Rondônia state).
In conclusion, our findings highlight a higher seroprevalence rate (IgG) for antibodies against hantavirus in the human population in Brazil, with a higher rate in the subtropical region (Atlantic Rain Forest) than in the tropical region (Amazon Forest). Degraded ecosystems allow close contact of humans with zoonoses, resulting in enhanced transmission of pathogens to humans. Particularly it is relevant because São Paulo state is one of the most densely populated states in Brazil. We are highlighting our findings to provide a better understanding of hantavirus infection and circulation in Brazil, specifically demonstrating hotspots that will require public health action to prevent a possible outbreak.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Felipe Alves Morais and Alexandre Pereira contributed equally to this work.
This study received financial support from FAPESP (05/01603-4). The authors would like to extend special thanks to José Maria Lopes (technical specialist at the ICB/USP laboratory), who helped them during sample collection in the field. They also thank Paulo S. da Costa, Fernando A. da Costa, João Ventura, and many other people who helped them in many different ways.