SARS-CoV-2 transmission dynamics in the urban-rural interface.

OBJECTIVES: As the world responds to the coronavirus outbreak, the role of public health in ensuring equitable health care that considers the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) dynamics in rural communities is still a challenge. The same suppression and mitigation measures have been implemented homogeneously, ignoring the differences between urban and rural areas. We propose an epidemiological model and simulate the dynamics of SARS-CoV-2 in urban and rural areas considering the interaction between these regions. STUDY DESIGN: This was a population modeling study. METHODS: A compartmental epidemiological model was formulated to simulate the transmission of SARS-CoV-2 in urban and rural areas. We use the model to investigate the impact of control strategies focused on the urban-rural interface to contain the epidemic size of SARS-CoV-2 in rural areas. RESULTS: Considering five different levels for the exposition rate in urban areas and keeping intrarural and urban-rural exposition rates fixed, the preventive measures reduce the size and delay the peak for the urban infectives. The response of infected individuals and cumulative deaths in rural areas upon changes in the urban dynamics was small but not negligible. On the other hand, preventive measures focused on the urban-rural interface impact the number of infected individuals and deaths in rural areas. CONCLUSIONS: The maintenance of SARS-CoV-2 in rural areas depends on the interaction of individuals at the urban-rural interface. Thus, restrictive measures established by the governments would not be required within rural areas. We highlight the importance of focused preventive measures on the urban-rural interface to reduce the exposure and avoid the transmission of SARS-CoV-2 to rural communities.

Generation of oxyradicals (O2. and H2O2), mitochondrial activity and induction of apoptosis of PBMC of Cyprinus carpio carpio treated in vivo with halomethanes and with recombinant HSP60 kDa and with LPS of Klebsiella pneumoniae.

Halomethanes (HM) can be immunotoxic in mammals; however, in the fish immune system HM effects are unknown. In the current study, we evaluated the mitochondrial activity (MA) by MTT, induction of apoptosis by SubG0 technique and quantified serum ROS concentration (O2. and H2O2) and ROS production in PBMC of Cyprinus carpio carpio treated i.p. with CH2Cl2, CHCl3 and BrCHCl2 (0.004-40.0 mg/kg) for 96 h. Positive controls were recombinant heat shock protein of 60 kDa (rHSP60 kDa) of Klebsiella pneumoniae and its LPS. In addition, for in vitro PBMC cultures, two culture media and two sources of sera were tested. Both positive controls increased the MA more than 4-fold as well as the production of O2. (26-fold) and H2O2 (5-fold) compared to their controls. HM induced different effects on MA, ROS production and an induction of apoptosis, depending on the chlorination patterns and the dose; however, a systemic damage prevails. To fish treated with CH2Cl2, the apoptosis was related with serum ROS concentration and with MA. In contrast, in fish dosed with CHCl3 relationships were not found, deducing a systemic damage. However, in fish treated with BrCHCl2, serum O2. concentration and in vitro ROS generation performed by PBMC were involved in the induction of apoptosis of these cells but not with MA suggesting also immunotoxic effects. The current study demonstrated that HMs are immunomodulators increasing an acute inflammatory response and that rHSP60kDA of K. pneumoniae and its LPS are appropriate antigens to assess the immune response of C. c. carpio.

Extreme genetic diversity among Pirital virus (Arenaviridae) isolates from western Venezuela.

Pirital-like virus isolates from rodents collected in a variety of habitats within a six-state area of central Venezuela were analyzed genetically by amplifying a portion of the nucleocapsid protein gene using RT-PCR. Comparisons of the sequences from 30 selected Pirital-like virus isolates demonstrated up to 26% divergence in nucleotide sequences and up to 16% divergence in deduced amino acid sequences. Within the Pirital monophyletic group, 14 distinct lineages or genotypes, differing by at least 6% in nucleotide sequences, were identified. Although sample sizes were small for some lineages, many of the different genotypes were sampled in only one region or locality, suggesting allopatric divergence. Complement fixation tests with representatives of the most divergent Pirital virus lineages failed to delineate multiple species or subtypes within the Pirital clade. These results indicate that the previously proposed 12% nucleocapsid protein amino acid sequence divergence cutoff value for delineating arenavirus species is not appropriate for the entire family. When individual clones were examined from PCR amplicons, a mean of 0.17% sequence diversity vs the consensus sequences was detected, suggesting diverse quasispecies populations within infected rodent hosts. Possible explanations for the extreme genetic diversity within and among Pirital virus populations in infected rodents are discussed.

Guanarito virus (Arenaviridae) isolates from endemic and outlying localities in Venezuela: sequence comparisons among and within strains isolated from Venezuelan hemorrhagic fever patients and rodents.

Despite intensive surveillance, Venezuelan hemorrhagic fever (VHF), caused by Guanarito (GTO) virus, has been detected in only a small region of western Venezuela. To determine whether VHF is associated with a particular regional GTO virus strain(s), 29 isolates from rodents and humans throughout the surrounding regions were analyzed by partial sequencing of the nucleocapsid protein gene. Phylogenetic trees delineated nine distinct GTO genotypes that differ by 4-17% in nucleotides and up to 9% in amino acid sequences; most appeared to be restricted to discrete geographic regions, although a few genotypes were isolated in several locations. Each genotype included at least one strain recovered from a rodent, but only two genotypes were isolated from VHF cases. The presence outside of the endemic/epidemic region of two genotypes isolated also from VHF cases suggests that human pathogenic viruses occur outside of the endemic zone, but do not frequently infect people and/or cause apparent disease there. VHF does not appear to be associated with a GTO virus genotype that is restricted to a certain rodent species. When quasispecies diversity was examined, rodent isolates had higher sequence variation than human isolates. One rodent isolate included a mixture of two phylogenetically distinct genotypes, suggesting a dual infection.

[Serotypes and genotypes of dengue virus circulating in Venezuela, 1990-1997]. / Serotipos y genotipos de virus dengue circulantes en Venezuela, 1990-1997.

Due to the increasing severity of hemorrhagic dengue epidemics during the last years in Venezuela, a retrospective analysis was conducted to identify the behaviour of the dengue virus serotypes circulating in the country and the molecular evolution of dengue virus serotype 2. The data presented here indicates that dengue virus serotypes 1, 2 and 4 are endemic in Venezuela, they circulate simultaneously around the year in the biggest urban cities, however, one particular serotype is predominant during an epidemic period and replaces the virus serotype dominant during the previous epidemic period. The increased severity of dengue fever since 1989 in Venezuela might be associated to the introduction of the Asiatic genotype of virus which replaced the autochthonous Caribbean genotype. The Asiatic genotype is recognised as a more virulent virus.

Incidencia de la infección por virus pirital en roedores de la especie sigmodón alstoni: efectos de la infección sobre la especie / Incidence of the pirital virus infection in rodents of the sigmodon alstony species: effects of the infection on the specie

El virus Pirital es un nuevo arenavirus descubierto en Venezuela, sin embargo no existen evidencias de que pueda ser un virus patógeno para el humano. Sus efectos en el roedor que le sirve de reservorio natural: sigmodón alstoni se analiza en el presente estudio. Un total de 478 roedores: S. alstoni fueron capturados entre junio de 1994 a diciembre de 1995 en el Municipio Papelón, estado Portuguesa. Se recolectaron muestras de sangre y bazo para el aislamineto e identificación de virus en cultivo de células Vero E6. La densidad de la población de roedores S. alstoni mostró un patrón estacional con un máximo éxito de trampeo al final de la estación de sequía (Marzo-Abril). Esta variación temporal no estuvo correlacionada con variaciones en la prevalencia de infección por virus Pirital. El promedio de infección en la especie fue de 33,8 por ciento con un incremento no significativo en la prevalencia de infección entre animales juveniles y adultos. El efecto de la infección por el virus Pirital en el peso y tamaño del cuerpo de los roedores así como en la fertilidad, número de animales por camada, etc. no fue significativamente diferente cuando se compararon los animales infectados con los no infectados

Isolation and characterization of pirital virus, a newly discovered South American arenavirus.

Specific rodent species are principal hosts for each of the well-characterized members of the virus family Arenaviridae. Guanarito virus (Arenaviridae) is the etiologic agent of Venezuelan hemorrhagic fever. A previous study on the epidemiology of Venezuelan hemorrhagic fever revealed extensive arenavirus infection (presumed to be caused by Guanarito virus) in two rodent species. Sigmodon alstoni and Zygodontomys brevicauda, collected from the region of Venezuela in which the disease is endemic. In the present study, four arenavirus isolates recovered from the Municipality of Guanarito (two isolates each from S. alstoni and Z. brevicauda) were characterized to learn more about the natural rodent host relationships of Guanarito virus. Serologic tests and analyses of nucleocapsid protein gene sequence data indicated that the two isolates from Z. brevicauda are strains of Guanarito virus and that the two isolates from S. alstoni are representatives of a novel New World arenavirus (proposed name Pirital) that is antigenically and phylogenetically distinct from all known New World arenaviruses. The results of the present study provide further evidence that the cane mouse Z. brevicauda is a natural host of Guanarito virus and suggest that the cotton rat S. alstoni is the natural reservoir host of Pirital but not Guanarito virus.

Origins of dengue type 2 viruses associated with increased pathogenicity in the Americas.

The recent emergence and spread of dengue hemorrhagic fever in the Americas have been a major source of concern. Efforts to control this disease are dependent on understanding the pathogenicity of dengue viruses and their transmission dynamics. Pathogenicity studies have been hampered by the lack of in vitro or in vivo models of severe dengue disease. Alternatively, molecular epidemiologic studies which associate certain dengue virus genetic types with severe dengue outbreaks may point to strains with increased pathogenicity. The comparison of nucleotide sequences (240 bp) from the E/NS1 gene region of the dengue virus genome has been shown to reflect evolutionary relationships and geographic origins of dengue virus strains. This approach was used to demonstrate an association between the introduction of two distinct genotypes of dengue type 2 virus and the appearance of dengue hemorrhagic fever in the Americas. Phylogenetic analyses suggest that these genotypes originated in Southeast Asia and that they displaced the native, American genotype in at least four countries. Vaccination and other control efforts should therefore be directed at decreasing the transmission of these "virulent" genotypes.

Isolation, characterization and geographic distribution of Caño Delgadito virus, a newly discovered South American hantavirus (family Bunyaviridae).

Rodents collected from the Venezuelan llanos (plains) during field studies of viral hemorrhagic fever were tested for evidence of hantavirus infection. Hantavirus antibody was found in one (7.7%) of 13 Oryzomys bicolor, one (3.4%) of 29 Rattus rattus, 10 (6.0%) of 166 Sigmodon alstoni and one (2.2%) of 45 Zygodontomys brevicauda. Hantavirus-specific RNA was detected in lung tissues from four antibody-positive rodents: two S. alstoni from Portuguesa State and one S. alstoni each from Cojedes and Barinas States. A hantavirus isolate (herein identified as VHV-574) was recovered from lung tissue from a hantavirus RNA-positive S. alstoni collected from Portuguesa State. The results of serological tests and analyses of small and medium RNA segment nucleotide sequence data indicated that VHV-574 represents a novel hantavirus (proposed name 'Caño Delgadito') that is distinct from all previously characterized hantaviruses. The results of analyses of nucleotide sequence data from the four hantavirus RNA-positive S. alstoni suggested that Caño Delgadito virus is widely distributed in the Venezuelan llanos.

Field studies on the epidemiology of Venezuelan hemorrhagic fever: implication of the cotton rat Sigmodon alstoni as the probable rodent reservoir.

During February 1992, field studies on the epidemiology of Venezuelan hemorrhagic fever (VHF) were carried out in a rural area of Portuguesa State in central Venezuela. The objective of this work was to determine the prevalence of infection with Guanarito virus, the etiologic agent of VHF, among wild rodents and humans living within an endemic focus of the disease. A total of 234 rodents, representing nine different species, were collected and their spleens were cultured for virus. Thirty-one Guanarito virus isolates were made from two rodent species: 19 from 40 Sigmodon alstoni and 12 from 106 Zygodontomys brevicauda. Guanarito virus antibody rates among these two species were 5.1% and 15.0%, respectively. Nine of the 12 Z. brevicauda that yielded virus from their spleens also had Guanarito virus antibodies in their sera. In contrast, none of the 19 Guanarito virus-positive S. alstoni had antibodies to the virus. These data suggest that S. alstoni usually develops a persistent nonimmunizing infection with Guanarito virus, while Z. brevicauda develops an immunizing infection. Based on knowledge of the behavior of other human pathogenic arenaviruses, these results imply that S. alstoni is the principal rodent reservoir of Guanarito virus in nature. To determine the prevalence of Guanarito virus infection among humans in the same region, 195 people living near one of the rodent collecting sites were bled and their sera were tested for antibodies to the virus. Five individuals (2.6%) had Guanarito virus antibodies; all were adults, and two had been diagnosed previously as having VHF.(ABSTRACT TRUNCATED AT 250 WORDS)

Sigmodon alstoni potencial reservorio natural del virus Guanarito / Sigmodon alstoni: natural potential reservoirs of the Guanarito virus

La Fiebre Hemorrágica Venezolana es una enfermedad severa causada por el virus Guanarito que aparece en forma endemo-epidémica en Venezuela a partir de 1989. Los Arenavirus utilizan como reservorio a los roedores para persistir en la naturaleza, siendo específicos para la especie que les sirve como hospedador. La infección del humano ocurre por contacto con secreciones de estos animales. Para conocer el reservorio natural del virus Guanarito, se capturaron 256 ejemplares de roedores en 5 áreas representativas de los tipos de hábitat del Municipio Guanarito del Edo. Portuguesa. Los animales fueron clasificados en 9 especies y se recolectaron muestras de sangre y bazo para realizar estudios virológicos. El macerado de cada bazo fue inoculado en células VERO E6 para aislamiento viral y en la sangre se determinaron anticuerpos específicos para el virus Guanarito por la técnica de IFI. Los resultados indicaron una alta densidad de roedores en la Hoyada y la Arenosa donde las especies dominantes en orden e importancia fueron: Zygodontomys brevicauda, Sigmodon alstoni, Rattus rattus, Proechymys guairae y Oryzomys fulvecens. Todas estas especies se encontraron susceptibles a la infección por el virus Guanarito; el mayor porcentaje de roedores infetados se encontró en la especie Sigmodon alstoni (52,6 por ciento) y Zygodontomys brevicauda (26,3//). De especial interés fue el hallazgo que 9 de 13 animales de esta última especie, excretaba virus en presencia de anticuerpos humorales. Estos resultados indican que el virus Guanarito está ampliamente distribuido entre los roedores dominantes en esta zona del país, pero la especie Sigmodon alstoni es reservorio potencial del virus, las otras especies son reservorios que contribuyen a mantener el virus en la naturaleza y también constituyen una fuente de infección para el humano

Doxepin therapy for postprandial symptomatic hypoglycaemic patients: neurochemical, hormonal and metabolic disturbances.

1. Three oral glucose tolerance tests were performed in each of 32 symptomatic postprandial hypoglycaemic patients (before placebo, before doxepin therapy and after doxepin therapy). Plasma neurotransmitters were determined in parallel with assays of plasma insulin and glucose levels. 2. Three different types of patients were distinguished. Type I showed a low noradrenaline/adrenaline ratio, high dopamine levels and low platelet 5-hydroxytryptamine (serotonin) levels during basal periods. After a glucose load, late peaks of dopamine and free 5-hydroxytryptamine, which coincided with the symptoms but not with the nadir of plasma glucose, were observed. Type II showed a low basal plasma noradrenaline/adrenaline ratio. After a glucose load, progressive increases in adrenaline and decreases in glucose were seen. Adrenergic symptoms coincided with the nadir of glucose. Although type III patients showed hyperinsulinaemia after a glucose load similar to the other types of patient, they did not show hyperglycaemia, but rather exhibited a sustained and progressive reduction in plasma glucose. These patients were characterized by a high basal plasma noradrenaline/adrenaline ratio, high basal plasma levels of 4-hydroxy-3-methoxyphenylethyleneglycol and high basal levels of platelet 5-hydroxytryptamine, all of which increased after a glucose load. Systolic and diastolic blood pressure decreases paralleled reductions in heart rate and glucose. The nadir of plasma glucose occurred simultaneously with the appearance of symptoms (weakness, heartburn, oppressive chest pain, tension headache, abdominal cramps, dizziness, etc.). Therapy with doxepin led to disappearance of the symptoms within 3-4 weeks. Normalization of all other disordered variables (cardiovascular, metabolic and neurochemical, and the clonidine test) paralleled the disappearance of the symptoms. 3. Symptoms varied in the three types of patients and we conclude that they are related to hypoglycaemia-induced disorders of plasma neurotransmitters, rather than to hypoglycaemia per se. We postulate that an uncoping stress situation (type I and II patients) and depression (type III patients) underlie the physiopathological mechanisms.

Trypanosoma (Herpetosoma) rangeli Tejera, 1920: study of the effects of the parasite on the vector.

For evaluation of the possible pathogenicity of Trypanosoma (Herpetosoma) rangeli Tejera, 1920 to the triatomid vector, first-stage nymphs of laboratory-bred insects were engorged upon albino mice showing average parasitemias of 2 x 10(6) and 2 x 10(5) trypanosomes/ml blood. The vector strains were: Rhodnius prolixus ("New" strain), Triatoma pallidipennis, and Triatoma vitticeps. An "Old" strain of R. prolixus (maintained 30 years in the laboratory) was also employed to check the effects of laboratory breeding. Other lots of nymphs of the same vector strains were fed on healthy mice as controls. T. rangeli produced intense infections in the gut and hemolymph of all the vector tested, with later differentiation in the salivary glands to metatrypomastigotes that could be transmitted by the bite of the insect and establish infections in healthy mice. No statistically significant differences whatever between infected and control bugs were found for degree of engorgement, percentage or cause of mortality, molting time, oviposition/female, hatching time, percentage of hatching, or duration of life cycle. The possible role of experimental methodology in producing pathology in infected insects, and the epidemiological significance of a strain of T. rangeli non-pathogenic to the vector are discussed.

Air pollution and forest decline near Mexico City.

The forests of Abies religiosa Schl. et Cham. in the north and the northeast slopes of the mountains of the southwestern region of the Valley of Mexico are in an acute process of decline, particularly the fir forest of the Cultural and Recreational Park Desierto de los Leones. The mortality of the trees began in 1981, and by 1987 30% of the trees of the Park had died; the mortality continues. The surviving trees are in a very poor crown condition, having thin crowns with many dead branches. in the light of current knowledge air pollution, in particular the oxidant gases (ozone), are the primary cause of decline, but other conditions or agents (age of the trees and diseases) could be contributing factors in the dying of the trees.