[Seroprevalence of infection by St. Louis encephalitis virus in the Province of Formosa]. / Seroprevalencia de infección por el virus encefalitis San Luis en la Provincia de Formosa.

The aim of this work was to determine the prevalence of antibodies against St. Louis encephalitis virus (SLE) in human sera provided by the Laboratory of Epidemiological Surveillance from Formosa District (Province of Formosa, Argentina) in 1995 and 1997. The tests used for this study were hemagglutination inhibition (HI) and neutralization (NT). The screening performed by NT test showed prevalences of 21% (60/284) and 32% (50/157) of antibodies in samples obtained in 1995 and 1997 respectively. In 1995, 14% of tested sera showed low titer of neutralizing antibodies (NT) (1/20 and 1/40) whereas in 1997, 19% of the sera presented titers of NT antibodies equal or greater than 1/80. It was observed that sera with low titers of NT antibodies (1/20-1/40) resulted negative in HI in the simultaneous titration of antibodies by NT and HI whereas other sera presented high titers for both tests. This relation between the low and the high titers of antibodies indicates the presence of past and recent infections and the continuous circulation of this virus. Moreover, the prevalence of NT antibodies in the surveyed population increased significantly in 2 years (p < 0.0075) confirming the endemicity of this agent in this area and showing the need to perform studies of non-confirmed viral etiology febrile diseases to determine its importance in human pathogenicity.

Seroprevalencia de infección por el virus encefalitis San Luis en la Provincia de Formosa. / [Seroprevalence of infection by St. Louis encephalitis virus in the Province of Formosa]

The aim of this work was to determine the prevalence of antibodies against St. Louis encephalitis virus (SLE) in human sera provided by the Laboratory of Epidemiological Surveillance from Formosa District (Province of Formosa, Argentina) in 1995 and 1997. The tests used for this study were hemagglutination inhibition (HI) and neutralization (NT). The screening performed by NT test showed prevalences of 21

(60/284) and 32

(50/157) of antibodies in samples obtained in 1995 and 1997 respectively. In 1995, 14

of tested sera showed low titer of neutralizing antibodies (NT) (1/20 and 1/40) whereas in 1997, 19

of the sera presented titers of NT antibodies equal or greater than 1/80. It was observed that sera with low titers of NT antibodies (1/20-1/40) resulted negative in HI in the simultaneous titration of antibodies by NT and HI whereas other sera presented high titers for both tests. This relation between the low and the high titers of antibodies indicates the presence of past and recent infections and the continuous circulation of this virus. Moreover, the prevalence of NT antibodies in the surveyed population increased significantly in 2 years (p < 0.0075) confirming the endemicity of this agent in this area and showing the need to perform studies of non-confirmed viral etiology febrile diseases to determine its importance in human pathogenicity.

Detection of picobirnavirus in HIV-infected patients with diarrhea in Argentina.

Diarrhea due to enteric pathogens is an important complication of advanced HIV infection. Picobirnaviruses are agents recently linked with human enteritis. In total, 197 fecal samples collected from HIV-infected and noninfected patients with and without diarrhea were investigated for the presence of rotavirus and picobirnavirus by polyacrylamide gel electrophoresis. Picobirnavirus was detected in 8.8% of 57 HIV-infected patients with diarrhea, but it was detected in neither those without diarrhea (p<.018) nor in the group of subjects uninfected with HIV (p<.022). All genomic electropherotypes of picobirnavirus strains had a wide pattern. Picobirnavirus genome segments varied in size between 2.4 and 2.7 and 1.6 and 1.9 kbp for the slow and fast migrating bands, respectively. Rotaviruses were not detected in any of the clinical groups studied. Two methods for the extraction of nucleic acid-phenol/chloroform and guanidinium thiocynate (GTC)/silica-were compared. Detection of picobirnavirus by polyacrylamide gel electrophoresis was 2.5 times more sensitive following guanidinium thiocynate RNA extraction. This investigation offers preliminary results about the circulation of picobirnavirus in HIV-infected patients in Córdoba, Argentina.

PIP: In 1988, a new group of viruses containing a bisegmented double-stranded RNA genome was described and named "picobirnavirus" (PBV). Viruses with similar properties have subsequently been found in fecal specimens collected from HIV-infected and noninfected patients with gastrointestinal symptoms in several countries. The present study used polyacrylamide gel electrophoresis (PAGE) to examine fecal specimens from 197 HIV infected and noninfected adults, with and without diarrhea, from Cordoba, Argentina, for rotavirus and PBV. PBVs were detected in the stools of 5 HIV-infected patients with diarrhea (8.8%), but in none of the other subgroups (HIV-positive patients without diarrhea, HIV-negative patients with diarrhea, HIV-negative patients without diarrhea). 3 of the 5 stool samples positive for PBV were also positive for intestinal parasites (mixed infection), but these parasites were found with equal frequency in HIV-infected patients without diarrhea. Rotaviruses were not detected in any of the subgroups. PBV genome segments varied in size between 2.4-2.7 and 1.6-1.9 kbp for the slow and fast migrating bands, respectively. PBV detection by the PAGE technique was 2.5 times more sensitive after guanidinium thiocyanate RNA extraction. Further research is required to determine the duration of excretion of PBVs in HIV-infected patients with diarrhea and understand the immune response to infection.

Hepatitis B and C virus sexual transmission among homosexual men.

OBJECTIVE: We estimated hepatitis B virus (HBV) and hepatitis C virus (HCV) sexual transmission among homosexual men. METHODS: Two hundred twenty-eight homosexually active men attending two clinical centers and presenting no risk factors except for sexual exposure were interviewed, and a blood sample was drawn. HBV marker test was performed using enzyme-linked immunosorbent assay (ELISA) and radioimmunoassay, and HCV was tested using ELISA-2 and recombinant immunoblot assay-2. RESULTS: HBV and HCV infection prevalence rates were 34.4% and 12.7%, respectively. Using logistic regression analysis including sexual exposure and controlling for confounders, we found that anal receptive intercourse (odds ratio [OR] = 4.01; 95% confidence interval [CI] = 1.34-11.94), duration of homosexuality (OR = 3.43; 95% CI = 1.29-9.12), insertive anilingus (OR = 2.02; 95% CI = 1.06-3.87), and sexually transmitted diseases (OR = 1.87; 95% CI = 1.00-3.47) were independently associated with the risk of HBV sexual transmission. We did not find any association between sexual behavior and HCV transmission. CONCLUSIONS: Sexual behavior is a plausible explanatory factor of HBV sexual transmission among homosexual men. Further evidence is needed to elucidate the occurrence and the efficiency of HCV sexual transmission in the absence of other risk factors.