Distribution of influenza virus types by age using case-based global surveillance data from twenty-nine countries, 1999-2014.

BACKGROUND: Influenza disease burden varies by age and this has important public health implications. We compared the proportional distribution of different influenza virus types within age strata using surveillance data from twenty-nine countries during 1999-2014 (N=358,796 influenza cases). METHODS: For each virus, we calculated a Relative Illness Ratio (defined as the ratio of the percentage of cases in an age group to the percentage of the country population in the same age group) for young children (0-4 years), older children (5-17 years), young adults (18-39 years), older adults (40-64 years), and the elderly (65+ years). We used random-effects meta-analysis models to obtain summary relative illness ratios (sRIRs), and conducted meta-regression and sub-group analyses to explore causes of between-estimates heterogeneity. RESULTS: The influenza virus with highest sRIR was A(H1N1) for young children, B for older children, A(H1N1)pdm2009 for adults, and (A(H3N2) for the elderly. As expected, considering the diverse nature of the national surveillance datasets included in our analysis, between-estimates heterogeneity was high (I2>90%) for most sRIRs. The variations of countries' geographic, demographic and economic characteristics and the proportion of outpatients among reported influenza cases explained only part of the heterogeneity, suggesting that multiple factors were at play. CONCLUSIONS: These results highlight the importance of presenting burden of disease estimates by age group and virus (sub)type.

Congenital Transmission of Trypanosoma cruzi in Argentina, Honduras, and Mexico: An Observational Prospective Study.

Compared with South America, there is a lack of epidemiologic studies about the risk of congenital transmission of Trypanosoma cruzi in Central America and Mexico. It has been suggested that T. cruzi genotypes might differ by region and that congenital transmission might vary according to the parasite's genotype. Our objective was to compare T. cruzi congenital transmission rates in three countries. We performed an observational prospective study in 2011-2014 enrolling women at delivery in one hospital in Argentina, two hospitals in Honduras, and two hospitals in Mexico. Congenital T. cruzi infection was defined as the presence of one or more of the following criteria: presence of parasites in cord blood (direct parasitological microscopic examination) with positive polymerase chain reaction (PCR) in cord blood, presence of parasites in infant's blood at 4-8 weeks (direct parasitological microscopic examination), and persistence of T. cruzi-specific antibodies at 10 months, as measured by at least two tests. Among 28,145 enrolled women, 347 had at least one antibody rapid test positive in cord blood and a positive enzyme-linked immunosorbent assay in maternal blood. PCR in maternal blood was positive in 73.2% of the cases, and genotyping identified a majority of non-TcI in the three countries. We found no (0.0%; 95% confidence interval [CI]: 0.0, 2.0) confirmed congenital case in Honduras. Congenital transmission was 6.6% (95% CI: 3.1, 12.2) in Argentina and 6.3% (95% CI: 0.8, 20.8) in Mexico. Trypanosoma cruzi non-TcI predominated and risks of congenital transmission were similar in Argentina and Mexico.

Characteristics of seasonal influenza A and B in Latin America: Influenza surveillance data from ten countries.

INTRODUCTION: The increased availability of influenza surveillance data in recent years justifies an actual and more complete overview of influenza epidemiology in Latin America. We compared the influenza surveillance systems and assessed the epidemiology of influenza A and B, including the spatio-temporal patterns of influenza epidemics, in ten countries and sub-national regions in Latin America. METHODS: We aggregated the data by year and country and characteristics of eighty-two years were analysed. We calculated the median proportion of laboratory-confirmed influenza cases caused by each virus strain, and compared the timing and amplitude of the primary and secondary peaks between countries. RESULTS: 37,087 influenza cases were reported during 2004-2012. Influenza A and B accounted for a median of 79% and, respectively, 21% of cases in a year. The percentage of influenza A cases that were subtyped was 82.5%; for influenza B, 15.6% of cases were characterized. Influenza A and B were dominant in seventy-five (91%) and seven (9%) years, respectively. In half (51%) of the influenza A years, influenza A(H3N2) was dominant, followed by influenza A(H1N1)pdm2009 (41%) and pre-pandemic A(H1N1) (8%). The primary peak of influenza activity was in June-September in temperate climate countries, with little or no secondary peak. Tropical climate countries had smaller primary peaks taking place in different months and frequently detectable secondary peaks. CONCLUSIONS: We found that good influenza surveillance data exists in Latin America, although improvements can still be made (e.g. a better characterization of influenza B specimens); that influenza B plays a considerable role in the seasonal influenza burden; and that there is substantial heterogeneity of spatio-temporal patterns of influenza epidemics. To improve the effectiveness of influenza control measures in Latin America, tropical climate countries may need to develop innovative prevention strategies specifically tailored to the spatio-temporal patterns of influenza in this region.

Temporal Patterns of Influenza A and B in Tropical and Temperate Countries: What Are the Lessons for Influenza Vaccination?

INTRODUCTION: Determining the optimal time to vaccinate is important for influenza vaccination programmes. Here, we assessed the temporal characteristics of influenza epidemics in the Northern and Southern hemispheres and in the tropics, and discuss their implications for vaccination programmes. METHODS: This was a retrospective analysis of surveillance data between 2000 and 2014 from the Global Influenza B Study database. The seasonal peak of influenza was defined as the week with the most reported cases (overall, A, and B) in the season. The duration of seasonal activity was assessed using the maximum proportion of influenza cases during three consecutive months and the minimum number of months with ≥80% of cases in the season. We also assessed whether co-circulation of A and B virus types affected the duration of influenza epidemics. RESULTS: 212 influenza seasons and 571,907 cases were included from 30 countries. In tropical countries, the seasonal influenza activity lasted longer and the peaks of influenza A and B coincided less frequently than in temperate countries. Temporal characteristics of influenza epidemics were heterogeneous in the tropics, with distinct seasonal epidemics observed only in some countries. Seasons with co-circulation of influenza A and B were longer than influenza A seasons, especially in the tropics. DISCUSSION: Our findings show that influenza seasonality is less well defined in the tropics than in temperate regions. This has important implications for vaccination programmes in these countries. High-quality influenza surveillance systems are needed in the tropics to enable decisions about when to vaccinate.

Timing of influenza epidemics and vaccines in the American tropics, 2002-2008, 2011-2014.

BACKGROUND: Influenza-associated illness results in increased morbidity and mortality in the Americas. These effects can be mitigated with an appropriately chosen and timed influenza vaccination campaign. To provide guidance in choosing the most suitable vaccine formulation and timing of administration, it is necessary to understand the timing of influenza seasonal epidemics. OBJECTIVES: Our main objective was to determine whether influenza occurs in seasonal patterns in the American tropics and when these patterns occurred. METHODS: Publicly available, monthly seasonal influenza data from the Pan American Health Organization and WHO, from countries in the American tropics, were obtained during 2002-2008 and 2011-2014 (excluding unseasonal pandemic activity during 2009-2010). For each country, we calculated the monthly proportion of samples that tested positive for influenza. We applied the monthly proportion data to a logistic regression model for each country. RESULTS: We analyzed 2002-2008 and 2011-2014 influenza surveillance data from the American tropics and identified 13 (81%) of 16 countries with influenza epidemics that, on average, started during May and lasted 4 months. CONCLUSIONS: The majority of countries in the American tropics have seasonal epidemics that start in May. Officials in these countries should consider the impact of vaccinating persons during April with the Southern Hemisphere formulation.

Prevalence of pfhrp2 and pfhrp3 gene deletions in Puerto Lempira, Honduras.

BACKGROUND: Recent studies have demonstrated the deletion of the histidine-rich protein 2 (PfHRP2) gene (pfhrp2) in field isolates of Plasmodium falciparum, which could result in false negative test results when PfHRP2-based rapid diagnostic tests (RDTs) are used for malaria diagnosis. Although primary diagnosis of malaria in Honduras is determined based on microscopy, RDTs may be useful in remote areas. In this study, it was investigated whether there are deletions of the pfhrp2, pfhrp3 and their respective flanking genes in 68 P. falciparum parasite isolates collected from the city of Puerto Lempira, Honduras. In addition, further investigation considered the possible correlation between parasite population structure and the distribution of these gene deletions by genotyping seven neutral microsatellites. METHODS: Sixty-eight samples used in this study, which were obtained from a previous chloroquine efficacy study, were utilized in the analysis. All samples were genotyped for pfhrp2, pfhrp3 and flanking genes by PCR. The samples were then genotyped for seven neutral microsatellites in order to determine the parasite population structure in Puerto Lempira at the time of sample collection. RESULTS: It was found that all samples were positive for pfhrp2 and its flanking genes on chromosome 8. However, only 50% of the samples were positive for pfhrp3 and its neighboring genes while the rest were either pfhrp3-negative only or had deleted a combination of pfhrp3 and its neighbouring genes on chromosome 13. Population structure analysis predicted that there are at least two distinct parasite population clusters in this sample population. It was also determined that a greater proportion of parasites with pfhrp3-(and flanking gene) deletions belonged to one cluster compared to the other. CONCLUSION: The findings indicate that the P. falciparum parasite population in the municipality of Puerto Lempira maintains the pfhrp2 gene and that PfHRP2-based RDTs could be considered for use in this region; however continued monitoring of parasite population will be useful to detect any parasites with deletions of pfhrp2.

Congenital transmission of Trypanosoma cruzi in Argentina, Honduras, and Mexico: study protocol.

BACKGROUND: Trypanosoma cruzi has been divided into Discrete Typing Units I and non-I (II-VI). T. cruzi I is predominant in Mexico and Central America, while non-I is predominant in most of South America, including Argentina. Little is known about congenital transmission of T. cruzi I. The specific aim of this study is to determine the rate of congenital transmission of T. cruzi I compared to non-I. METHODS/DESIGN: We are conducting a prospective study to enroll at delivery, 10,000 women in Argentina, 7,500 women in Honduras, and 13,000 women in Mexico. We are measuring transmitted maternal T. cruzi antibodies by performing two rapid tests in cord blood (Stat-Pak, Chembio, Medford, New York, and Trypanosoma Detect, InBios, Seattle, Washington). If at least one of the results is positive, we are identifying infants who are congenitally infected by performing parasitological examinations on cord blood and at 4-8 weeks, and serological follow-up at 10 months. Serological confirmation by ELISA (Wiener, Rosario, Argentina) is performed in cord and maternal blood, and at 10 months. We also are performing T. cruzi standard PCR, real-time quantitative PCR and genotyping on maternal venous blood and on cord blood, and serological examinations on siblings. Data are managed by a Data Center in Montevideo, Uruguay. Data are entered online at the sites in an OpenClinica data management system, and digital pictures of data forms are sent to the Data Center for quality control. Weekly reports allow for rapid feedback to the sites.

Letter to the editor: molecular genotyping of Dengue Virus Types 2 and 4 from the Guatemalan and Honduran Epidemics of 2007 using the envelope glycoprotein gene.

Eight serum specimens collected from dengue patients in Guatemala and Honduras during the Central American epidemic of 2007 were analyzed. Virus identification and serotyping performed by a nested RT-PCR assay revealed two DENV-1 isolates from Guatemala, four DENV-2 isolates, two each from Guatemala and Honduras, and two DENV-4 isolates from Honduras. Viral genotyping determined by phylogenetic analysis of the complete envelope gene sequences demonstrated that the DENV-2 isolates from Guatemala and Honduras fell into the American/Asian Genotype III, and were most closely related to DENV-2/NI/BID-V2683-1999 isolated from a dengue case in Nicaragua in 1999; and the DENV-4 F07-076 isolate from Honduras belonged to genotype II, and was most closely related to DENV-4/US/BID-V1093/1998 isolated from Puerto Rico in 1998. Our results suggest that the 2007 dengue outbreaks in Guatemala and Honduras were most likely caused by the re-emergence of earlier, indigenous DENV strains rather than by newly introduced strains and there were at least three serotypes of DENV co-circulating during the 2007 Central American epidemics.

Manual de procedimentos de tecnicas para el diagnostico del dengue

Presenta un estudio de la tecnicas adoptadas para el diagnostico del dengue. Aborda la seguridad en los laboratorios y los principios para trabajar en un laboratorio con especimenes infectados con virus, además de muchas otras abordajes. Documento en formato PDF, requiere Acrobat Reader.

Assessment of left ventricular diastolic function by radionuclide ventriculography at rest and exercise in subclinical hypothyroidism, and its response to L-thyroxine therapy.

Hypothyroidism is associated with intrinsic myocardial changes reflected by alterations in contractility and relaxation. Diastolic function, however, rather than systolic cardiac function, seems to be mostly impaired by thyroid hormone deprivation. Our aim was to evaluate diastolic function at rest and during maximal exercise by means of radionuclide ventriculography in subclinical hypothyroidism before and after restoration of euthyroidism. Ten subclinical hypothyroid patients (50 +/- 8.7 years) (thyroid-stimulating hormone 11 +/- 4.2 microUI/ml) without cardiac disease were studied before and 6 months after levothyroxine (L-T(4)) replacement (thyroid-stimulating hormone 1.9 +/- 1.1 microUI/ml). We compared the basal and post-therapy cardiac parameters with a control group of 14 euthyroid patients (52.5 +/- 10 years) (thyroid-stimulating hormone 2.5 +/- 1.2 microUI/ml). Multigated equilibrium radionuclide ventriculography was performed to assess systolic and diastolic ventricular function. Student's t and paired Student's t tests were applied for statistical analysis. We found a significant difference between the time to peak filling rate (TPFR) at rest before (0.241 +/- 0.002 ms) and after (0.190 +/- 0.012 ms) treatment with L-T(4). A significant difference that disappeared after restoration of euthyroidism was also observed between the basal TPFR values of the subclinical hypothyroid patients and the control group (0.189 +/- 0.01 ms). The same pattern was observed at maximal exercise. Thus, TPFR, a parameter of left ventricular (LV) diastolic function measured by radionuclide ventriculography, is impaired in subclinical hypothyroid patients both at rest and during exercise and returns to normal values after L-T(4) therapy.