Arboviral etiologies of acute febrile illnesses in Western South America, 2000-2007

BACKGROUND

Arthropod-borne viruses (arboviruses) are among the most common agents of human febrile illness worldwide and the most important emerging pathogens, causing multiple notable epidemics of human disease over recent decades. Despite the public health relevance, little is know about the geographic distribution, relative impact, and risk factors for arbovirus infection in many regions of the world. Our objectives were to describe the arboviruses associated with acute undifferentiated febrile illness in participating clinics in four countries in South America and to provide detailed epidemiological analysis of arbovirus infection in Iquitos, Peru, where more extensive monitoring was conducted.

METHODOLOGY/FINDINGS

A clinic-based syndromic surveillance system was implemented in 13 locations in Ecuador, Peru, Bolivia, and Paraguay. Serum samples and demographic information were collected from febrile participants reporting to local health clinics or hospitals. Acute-phase sera were tested for viral infection by immunofluorescence assay or RT-PCR, while acute- and convalescent-phase sera were tested for pathogen-specific IgM by ELISA. Between May 2000 and December 2007, 20,880 participants were included in the study, with evidence for recent arbovirus infection detected for 6,793 (32.5%). Dengue viruses (Flavivirus) were the most common arbovirus infections, totaling 26.0% of febrile episodes, with DENV-3 as the most common serotype. Alphavirus (Venezuelan equine encephalitis virus [VEEV] and Mayaro virus [MAYV]) and Orthobunyavirus (Oropouche virus [OROV], Group C viruses, and Guaroa virus) infections were both observed in approximately 3% of febrile episodes. In Iquitos, risk factors for VEEV and MAYV infection included being male and reporting to a rural (vs urban) clinic. In contrast, OROV infection was similar between sexes and type of clinic.

CONCLUSIONS/SIGNIFICANCE

Our data provide a better understanding of the geographic range of arboviruses in South America and highlight the diversity of pathogens in circulation. These arboviruses are currently significant causes of human illness in endemic regions but also have potential for further expansion. Our data provide a basis for analyzing changes in their ecology and epidemiology.

Etiology of acute undifferentiated febrile illness in the Amazon basin of Ecuador

We conducted a longitudinal observational study of 533 patients presenting to two hospitals in the Ecuadorean Amazon basin with acute undifferentiated febrile illness (AUFI) from 2001 through 2004. Viral isolation, reverse transcription-polymerase chain reaction (RT-PCR), IgM seroconversion, and malaria smears identified pathogens responsible for fever in 122 (40.1%) of 304 patients who provided both acute and convalescent blood samples. Leptospirosis was found in 40 (13.2%), malaria in 38 (12.5%), rickettsioses in 18 (5.9%), dengue fever in 16 (5.3%), Q fever in 15 (4.9%), brucellosis in 4 (1.3%), Ilhéus infection in 3 (1.0%), and Venezuelan equine encephalitis (VEE), Oropouche, and St. Louis encephalitis virus infections in less than 1% of these patients. Viral isolation and RT-PCR on another 229 participants who provided only acute samples identified 3 cases of dengue fever, 2 of VEE, and 1 of Ilhéus. None of these pathogens, except for malaria, had previously been detected in the study area.

First case of HIV Type 1 subtype F among men who have sex with men in Colombia

To study the molecular epidemiology of human immunodeficiency virus (HIV) strains among men who have sex with men (MSM), the main high-risk group for HIV infection in Colombia, 113 HIV-positive MSM subjects recruited in Bogotá during the year 2002 were genotyped. By heteroduplex mobility assay (env HMA) all samples were classified as subtype B. Partial sequencing of the protease and the reverse transcriptase (Pro/RT) regions performed on a random subset of 10 samples revealed that nine were classified as subtype B, and one sample was subtype F. The specimen that is subtype F in pol and subtype B in env is likely to be is either a recombinant or a dual infection. In this study, we identify the HIV F subtype for the first time in Colombia.

Assessment of human immunodeficiency virus type 1 and risk practices among female commercial sex workers in Isla Margarita, Venezuela

Sexual transmission represents the principal mode of transmission for human immunodeficiency virus type 1 (HIV-1) worldwide. We examined the HIV-1 seroprevalence and risk factors for infection among 613 female commercial sex workers (FCSW) in Isla Margarita, Venezuela. Recruitment was conducted in street venues and working locations. None of the FCSW tested positive for HIV; this correlated with the low self-reported rates of sexually transmitted infections (6%), drug use (<20%), and alcohol abuse (12%). Condom use and safe-sex practices were found to be practiced regularly (>80% of time) with clients; however, such practices were found to be very uncommon in nonclient relations (<20% of the time). Understanding the sexual risk behaviors, beliefs, and drug use patterns of FCSW is important for future development of effective public prevention policies and educational campaigns aimed at decreasing the risk of infection with HIV-1 and other sexually transmitted infections among FCSW.

Molecular epidemiology of human immunodeficiency virus-infected individuals in Medellin, Colombia

To study the molecular epidemiology of human immunodeficiency virus type 1 (HIV-1) strains in Medellín, Colombia, 115 HIV-1-positive individuals who were recruited from an HIV outpatient hospital (Universitario San Vicente de Paul) during the period from July 2001 to January 2002 were genotyped. All samples were analyzed by envelope heteroduplex mobility assay and found to be subtype B. Twenty-four samples were randomly selected for sequencing of the protease and the reverse transcriptase regions; all isolates were found to be subtype B. Phylogenetic analysis of seven nearly full-length genomes showed that all samples were subtype B. This study shows that the HIV epidemic in Colombia continues to be dominated by the subtype B virus. The predominance of subtype B genotypes of HIV-1 strains in Medellín resembles what is seen in the nearby countries of Peru, Ecuador, and Venezuela.

Prevalences, genotypes, and risk factors for HIV transmission in South America

HIV cross-sectional studies were conducted among high-risk populations in 9 countries of South America. Enzyme-linked immunosorbent assay screening and Western blot confirmatory testing were performed, and env heteroduplex mobility assay genotyping and DNA sequencing were performed on a subset of HIV-positive subjects. HIV prevalences were highest among men who have sex with men (MSM; 2.0%-27.8%) and were found to be associated with multiple partners, noninjection drug use (non-IDU), and sexually transmitted infections (STIs). By comparison, much lower prevalences were noted among female commercial sex workers (FCSWs; 0%-6.3%) and were associated mainly with a prior IDU and STI history. Env subtype B predominated among MSM throughout the region (more than 90% of strains), whereas env subtype F predominated among FCSWs in Argentina and male commercial sex workers in Uruguay (more than 50% of strains). A renewed effort in controlling STIs, especially among MSM groups, could significantly lessen the impact of the HIV epidemic in South America.

Human immunodeficiency virus type 1 and other viral co-infections among young heterosexual men and women in Argentina

Infections with hepatitis C virus, (HCV), hepatitis B virus (HBV), and human T lymphotropic type I/II (HTLV-I/II) virus are commonly found in patients infected with human immunodeficiency virus type 1 (HIV-1). We conducted a seroepidemiologic study among 174 HIV-positive heterosexuals in Buenos Aires, Argentina in 1999. Evidence of exposure to HCV, HBV, and HTLV-I/II was found in 32%, 17%, and 5%, respectively. A higher prevalence of HBV infection was observed among males (33%) compared with females (12%; P < 0.05). Among women, a prior history of a sexually transmitted infection, injecting drug use (IDU), having had more than five lifetime sex partners, and having exchanged sex-for-goods were significantly associated with HCV infection, whereas an IDU history, syringe sharing, and having exchanged sex-for-goods were found to be associated with HBV infection. Among men, an IDU history and syringe/needle sharing were significantly associated with HCV infection. The IDU-related and sexual transmission of hepatitis viruses constitute a significant problem among young, HIV-infected, heterosexuals in Argentina.

High human immunodeficiency virus type 1 seroprevalence in men who have sex with men in Buenos Aires, Argentina: risk factors for infection

OBJECTIVE

To determine human immunodeficiency virus (HIV) seroprevalence in a sample of men who have sex with men (MSM) in Buenos Aires City and to identify risk factors associated with HIV type 1 infection.

METHODS

Participants were invited to receive HIV counselling and testing at "NEXO" (a gay non-governmental organization) by means of informative leaflets distributed in gay nightclubs, porno cinemas, gymnasiums, and in the streets. During the encounter, the study was explained by a trained social worker and individuals were invited to volunteer for the study. Diagnosis of HIV was performed using two screening tests and Western Blot assay was used as confirmatory.

RESULTS

Human immunodeficiency virus was detected in 96 (13.8%; 95% CI: 11.4-16.7) of 694 MSM. Fourteen (14.6%) of the 96 HIV-positive MSM were already aware of their HIV serostatus. In univariate analysis, HIV-1 infection (odds ratio [OR] >1.5) was found to be associated with older age (30-39 years), being unemployed, a previous sexually transmitted disease (STD) history, and having an HIV-positive partner. Cocaine consumption and irregular use of condoms with occasional partners were also found to be risk factors. In multivariate logistic regression analysis, being unemployed (OR = 3.42; 95% CI: 1.17-9.99) and having an HIV-positive partner (OR = 2.67; 95% CI: 1.09-6.52) remained significant risk factors.

DISCUSSION

The high HIV-1 prevalence observed suggests an urgent need for implementation of effective prevention campaigns. This represents the first cross-sectional epidemiological study of HIV among the high-risk group of MSM in Argentina.

Sexual transmission of hepatitis B virus, hepatitis C virus, and human immunodeficiency virus type 1 infections among male transvestite comercial sex workers in Montevideo, Uruguay

Prostitution may constitute a risk behavior for infection with hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV). We conducted a seroepidemiologic study among 200 male transvestite commercial sex workers (CSWs) in Montevideo, Uruguay in 1999. Evidence of exposure to HBV, HCV, and HIV was found in 101 (50.5%), 13 (6.5%), and 43 (21.5%) individuals, respectively. Positivity for HIV was correlated with both HBV (odds ratio [OR] = 2.15, 95% confidence interval [CI] = 1.01-4.67) and HCV (OR = 3.47, 95% CI = 0.90-12.79) infection. Predictors of infection were older age (> or = 26 years; P < 0.01) for all 3 viruses and time in CSW (> or = 5 years; P < 0.05) for HBV and HIV. Prior history of use of drugs (OR = 3.54, 95% CI = 1.09-11.52) and sexual contact with foreigners (OR = 9.2, 95% CI = 1.16-73.12) were found to be associated only with HCV infection. Sexual transmission of these viruses constitutes a significant problem among male transvestite CSWs.

Molecular Epidemiology of HIV Type 1 in Ecuador, Peru, Bolivia, Uruguay, and Argentina

Surveillance for HIV infection among people at increased risk was conducted in five countries in South America. Seroprevalence studies were conducted in more than 36,000 people in Ecuador, Peru, Boliva, Uruguay, and Argentina, along with genetic analysis of the HIV-1 strains. In all countries, the prevalence of HIV-1 among men who have sex with men (MSM) was high (3-30%), whereas the prevalence among female commercial sex workers (FCSMs) was low (0.3-6%). By envelope heteroduplex mobility assay, subtype B predominated in MSM communities and in FCSWs in Ecuador, Bolivia, and Peru. A new genetic screening assay, the multiregion hybridization assay for subtypes B and F (MHA-bf), was developed to improve large-scale genetic screening in South America. MHA-bf can screen four regions of the genome for subtype B or subtype F, and thus can detect most recombinants. The sensitivity of MHA-bf when applied to a panel of pure subtypes and CRF12_BF was 100%, and 88% of unique recombinants were also detected as recombinant. Using MHA-bf, more than 80% of samples from Ecuador, Peru, and Bolivia were classified as pure subtype B, whereas in Uruguay and Argentina this proportion was only 30 to 40%. BF recombinants were the most prevalent form of HIV-1 in Uruguay and Argentina. Subtype B is the most common subtype in countries lacking injecting drug use (IDU) epidemics, whereas BF recombinants are more common in countries where extensive IDU epidemics have been documented, suggesting the ontogeny of recombinant strains in particular risk groups in South America.

Diverse BF recombinants have spread widely since the introduction of HIV-1 into South America

OBJECTIVE

To describe the genetic diversity of HIV-1 in South America by full genome sequencing and analysis.

METHODS

Purified peripheral blood mononuclear cell DNA from HIV-infected individuals in Argentina, Uruguay and Bolivia was used to amplify full HIV-1 genomes. These were sequenced using the ABI 3100 automated sequencer and phylogenetically analysed.

RESULTS

Twenty-one HIV-1 strains from three South American countries, 17 of which were pre-screened by envelope heteroduplex mobility assay (HMA), were studied. Ten out of 10 HMA subtype F and four out of seven HMA subtype B strains were actually BF recombinants upon full genome analysis. Two BF recombinants from Argentina and two from Uruguay had the same structure, representing a new circulating recombinant form termed CRF12_BF(ARMA159). Twelve other BF recombinants had structures related to CRF12 but with additional segments of subtype B; each was unique. BF recombinants were temporally and geographically widespread, found as early as 1986-1987 in vertically infected Argentinian children and in Argentina, Uruguay, and Bolivia.