Sustaining measles and rubella elimination through the Regional Monitoring and Re-Verification Commission in the Americas.

The elimination of endemic rubella and measles transmission in the Region of the Americas was verified by the Pan American Health Organization's (PAHO) Regional Verification Commission in 2015 and 2016, respectively. Upon achieving this success, this Commission was disbanded. Shortly afterwards, the Region faced challenges in the post-elimination era, notably responding to and stopping transmission of imported measles cases.

Hepatitis C virus seroprevalence in multi-transfused patients in Colombia.

Background: Hepatitis C Virus (HCV) infection is a public health problem worldwide, with particular relevance in multi-transfused patients given that HCV is principally transmitted by exposure to infected blood.

Study Design: Between February and September 2003 a cross-sectional study was carried out in four hospital centres in Bogotá and Medellin, Colombia, to determine the risk factors for HCV infection in 500 multi-transfused patients.

Results: The study population was distributed in five groups: haemophilia, haemodyalsis, acute bleeding, ontological illnesses and sickle cell disease or thalassemia.

Molecular epidemiology of rabies in northern Colombia 1994-2003. Evidence for human and fox rabies associated with dogs.

During the period 2000-2003, wild grey foxes (Urocyon cinereoargenteus) in northern Colombia became infected with rabies. In order to derive phylogenetic relationships between rabies viruses isolated in foxes, dogs and humans in this region, 902 nt cDNA fragments containing the G-L intergenic region and encoding the cytoplasmic domain of protein G and a fragment of protein L were obtained by RT-PCR, sequenced and compared. Phylogenetic analysis showed that rabies viruses isolated in foxes, dogs and humans belonged to a single genetic variant.

Venezuelan equine encephalitis virus infection of spiny rats.

Enzootic strains of Venezuelan equine encephalitis virus (VEEV) circulate in forested habitats of Mexico, Central, and South America, and spiny rats (Proechimys spp.) are believed to be the principal reservoir hosts in several foci. To better understand the host-pathogen interactions and resistance to disease characteristic of many reservoir hosts, we performed experimental infections of F1 progeny from Proechimys chrysaeolus collected at a Colombian enzootic VEEV focus using sympatric and allopatric virus strains.

A phylogenetic reconstruction of the epidemiological history of canine rabies virus variants in Colombia.

Historically, canine rabies in Colombia has been caused by two geographically distinct canine variants of rabies virus (RV) which between 1992 and 2002 accounted for approximately 95% of Colombian rabies cases. Genetic variant 1 (GV1) has been isolated up until 1997 in the Central Region and the Department of Arauca, and is now considered extinct through a successful vaccination program. Genetic variant 2 (GV2) has been isolated from the northern Caribbean Region and continues to circulate at present.

Venezuelan equine encephalitis.

Venezuelan equine encephalitis virus (VEEV) remains a naturally emerging disease threat as well as a highly developed biological weapon. Recently, progress has been made in understanding the complex ecological and viral genetic mechanisms that coincide in time and space to generate outbreaks. Enzootic, equine avirulent, serotype ID VEEV strains appear to alter their serotype to IAB or IC, and their vertebrate and mosquito host range, to mediate repeated VEE emergence via mutations in the E2 envelope glycoprotein that represent convergent evolution.

[Molecular detection of yellow fever virus in human sera and mice brains].

A molecular method for the diagnosis of yellow fever virus infection was developed based on reverse transcription (RT) followed by polymerase chain reaction (PCR) amplification. Examinations were conducted on lyophilized sera from 3 fatal yellow fever cases and 4 fresh sera from 3 fatal cases and one from a symptomatic patient (positive IgM against yellow fever virus). Sera were extracted with TRIZOL-LS to isolate viral RNA for RT treatment and the PCR reaction included 2 primers sets designed specifically for yellow fever virus: sense, JM2104 (5'-CGTTGGGAGAGGAGATTC-3') y JM2249 (5'-TTCTTCACTTCGGTTGGG-3'), and antisense, JM2673 (5'-TCATCTGCCCTGCTTCTC-3') y JM2751 (5'-CCTCTCTGGTAAACATTCT-3').

[Molecular epidemiology of rabies epizootics in Colombia, 1994-2002: evidence of human and canine rabies associated with chiroptera].

Three urban rabies outbreaks have been reported in Colombia during the last two decades, one of which is ongoing in the Caribbean region (northern Colombia). The earlier outbreaks occurred almost simultaneously in Arauca (eastern Colombia) and in the Central region, ending in 1997. Phylogenetic relationships among rabies viruses isolated from the three areas were based on a comparison of cDNA fragments coding for the endodomain of protein G and a fragment of L protein obtained by RT-PCR.

Molecular epidemiology of rabies epizootics in Colombia: evidence for human and dog rabies associated with bats.

Three urban rabies outbreaks have been reported in Colombia during the last two decades, one of these is occurring in the Caribbean Region (northern Colombia), while the other two occurred almost simultaneously in Arauca (eastern Colombia) and in the Central Region and ended in 1997. In order to derive phylogenetic relationships between rabies viruses isolated in these three areas, 902 nt cDNA fragments encoding the cytoplasmic domain of protein G and a fragment of protein L were obtained by RT-PCR. These amplicons contained the G-L intergenic region and were sequenced to draw phylogenetic trees.

Natural enzootic vectors of Venezuelan equine encephalitis virus, Magdalena Valley, Colombia.

To characterize the transmission cycle of enzootic Venezuelan equine encephalitis virus (VEEV) strains believed to represent an epizootic progenitor, we identified natural vectors in a sylvatic focus in the middle Magdalena Valley of Colombia. Hamster-baited traps were placed into an active forest focus, and mosquitoes collected from each trap in which a hamster became infected were sorted by species and assayed for virus. In 18 cases, a single, initial, high-titered mosquito pool representing the vector species was identified.

Contrasting sylvatic foci of Venezuelan equine encephalitis virus in northern South America.

The ecology of Venezuelan equine encephalitis (VEE) virus transmission was compared at three enzootic foci: two forest sites in the Catatumbo region of western Venezuela that have yielded small numbers of virus isolates since the 1970s, and another focus in the middle Magdalena Valley of Colombia that has consistently yielded many VEE virus isolates. Our results demonstrated dramatic differences in VEE virus isolation rates from sentinel hamsters, as well as differences in mosquito species composition and captured mammals with antibodies to VEE virus, between the Colombian and Venezuelan study sites. The higher isolation rate of enzootic VEE virus in the Colombian site was associated with a more abundant fauna of spiny rats (Proechimys spp.

[Standardization of rabies virus genome amplification for its use in molecular epidemiology studies].

In order to improve the diagnosis and typification of rabies viruses at the Instituto Nacional de Salud National Reference Laboratory for rabies, we standardized techniques for the amplification of a 902 nucleotide DNA fragment, complementary to a selected region of the rabies virus genomic RNA. This region codes for a segment of both the glycoprotein and protein L, and contains the G-L intergenic noncoding region known as Pseudogen Psi. The standardized techniques included: 1) biological amplification of rabies viruses by intracerebral mouse inoculation; 2) total RNA extraction from the brains of infected mice, 3) RT-PCR amplification of a 902 nucleotide DNA fragment complementary to the selected RNA region.

[Indirect immunofluorescence as a supplementary test for confirming HIV-1 infection: the experience of the National Institute of Health, 1993-2000].

A team at the Colombian National Institute of Health (INS) has demonstrated the usefulness and suitability of the Immunofluorescent Antibody Test (IFAT) as a confirmatory assay for HIV-1. The assay followed a flow chart method recommended by the Pan American Health Organization (PAHO) and the Federal Center for AIDS of Canada. The specificity of the IFAT assay (IFI-VIH1-INS) for 925 serum samples was 100% when compared with two different Western blot (WB) assays.

Genetic diversity and relationships among Venezuelan equine encephalitis virus field isolates from Colombia and Venezuela.

During field studies of enzootic Venezuelan equine encephalitis (VEE) viruses associated with epizootic emergence, a large number of virus isolates were made in sylvatic foci of Venezuela and Colombia. To rapidly characterize these isolates, antigenic subtypes were determined by means of immunofluorescence and by single-strand conformational polymorphism (SSCP) analysis by use of an 856-bp fragment from the P62 gene, which we used to distinguish genetic variants. Representative isolates were sequenced to assess the sensitivity of SSCP to detect genetic differences.

Genetic and phenotypic changes accompanying the emergence of epizootic subtype IC Venezuelan equine encephalitis viruses from an enzootic subtype ID progenitor.

Recent studies have indicated that epizootic Venezuelan equine encephalitis (VEE) viruses can evolve from enzootic, subtype ID strains that circulate continuously in lowland tropical forests (A. M. Powers, M.

Genotype-specific RNA probes for direct identification of wild polioviruses by blot hybridization.

We have developed RNA probes for the direct identification of wild poliovirus isolates by blot hybridization. The probes are complementary to sequences of the first 30 to 32 codons of VP1, which evolve more extensively (approximately 1.5-fold) than the rest of VP1.

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.

Epidemic Venezuelan equine encephalitis in La Guajira, Colombia, 1995.

In 1995, the first Venezuelan equine encephalitis (VEE) outbreak in Colombia in 22 years caused an estimated 75,000 human cases, 3000 with neurologic complications and 300 fatal, in La Guajira State. Of the state's estimated 50,000 equines, 8% may have died. An epizootic IC virus, probably introduced from Venezuela, was rapidly amplified among unvaccinated equines.

Immunoglobulin M antibody response to measles virus following natural virus infection, primary vaccination, and reexposure to the virus.

Evaluation of the measles virus ELISA kit (Merck) to detect specific IgM as an indicator of primary measles antibody response was carried out. A modification of the manufacturer's cutoff value interpretation was introduced to allow for equivocal results in addition to positive and negative ones. With this modification, the test assayed gave an overall reproducibility of 96.

Establishment and characterization of a cell line from the mosquito Anopheles albimanus (Diptera: Culicidae).

A new cell line designated LSB-AA695BB, was established from embryos of the mosquito Anopheles albimanus. The primary culture was initiated in April, 1995, and the first passage was made 48 days later. Serial subcultures of the cells have been carried through 90 passage from Abril 1995 to February 1996.

Re-emergence of epidemic Venezuelan equine encephalomyelitis in South America. VEE Study Group.

Background: Venezuelan equine encephalomyelitis (VEE) virus has caused periodic epidemics among human beings and equines in Latin America from the 1920s to the early 1970s. The first major outbreak since 1973 occurred in Venezuela and Colombia during 1995, and involved an estimated 75,000 to 100,000 people. We report an epidemiological and virological investigation of this epidemic.

Transmission of HIV in dialysis centre.

In August, 1993, 13 dialysis patients at one dialysis centre in Colombia, South America, were found to be HIV positive, and this prompted an epidemiological investigation. We carried out a cohort study of all dialysis centre patients during January, 1992 to December, 1993 (epidemic period) to determine risk factors for HIV seroconversion. Haemodialysis and medical records were reviewed, dialysis centre staff and surviving patients were interviewed, and dialysis practices were observed.

Neutralization enzyme-linked immunosorbent assay for evaluation of immunity to measles virus.

A neutralization enzyme-linked immunosorbent (Nt-ELISA) assay for determination of protective immunity to measles virus was developed and evaluated. This procedure uses the same initial steps as performed to determine antibody titers by seroneutralization (Nt) test. However, a reduction in virus infectivity by neutralizing antibody was determined by quantitation of viral antigen using ELISA.

Modified seroneutralization assay for measles virus antibody detection.

We describe a simple, inexpensive, sensitive and specific modified seroneutralization assay for use on a wide scale to screen for the presence of measles antibodies. After only one reaction (1 h) and a 3-day incubation period at 37 degrees C, the test can be easily read using a rapid, inexpensive methylene blue/phenol staining procedure. The determination of protective antibody titres by modified and standard seroneutralization methods was strongly correlated (corr.