Browsing by Author "Abarca, K"

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    Dengue-1 virus isolation during first dengue fever outbreak on Easter Island, Chile
    (CENTER DISEASE CONTROL, 2003) Perret, C; Abarca, K; Ovalle, J; Ferrer, P; Godoy, P; Olea, A; Aguilera, X; Ferres, M
    Dengue virus was detected for the first time in Chile, in an outbreak of dengue fever on Easter Island. The virus was isolated in tissue culture and characterized by reverse transcription-polymerase chain reaction as being dengue type 1.
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    Early evolution of the human immunodeficiency virus type 1 subtype C epidemic in rural Malawi
    (2002) McCormack, GP; Glynn, JR; Crampin, AC; Sibande, F; Mulawa, D; Bliss, L; Broadbent, P; Abarca, K; Pönnighaus, JM; Fine, PEM; Clewley, JP
    We have tracked the early years of the evolution of the human immunodeficiency virus type 1 (HIV-1) epidemic in a rural district of central east Africa from the first documented introductions of subtypes A, D, and C to the present predominance of subtype C. The earliest subtype C sequences ever reported are described. Blood samples were collected on filter papers from 1981 to 1984 and from 1987 to 1989 from more than 44,000 individuals living in two areas of Karonga District, Malawi. These samples included HIV-1-positive samples from 200 people. In 1982 to 1984, HIV-1 subtypes A, C, and D were all present, though in small numbers. By 1987 to 1989, 152 (90%) of a total of 168 sequences were subtype C and AC, AD, and DC recombinants had emerged. Four of the subtype C sequences from 1983 to 1984 were closely related and were found at the base of a large cluster of low diversity that by the late 1980s accounted for 40% of C sequences. The other two early C sequences fell into a separate and more diverse cluster. Three other clusters containing sequences from the late 1980s were identified. Each cluster contained at least one sample from a person who had recently arrived in the district. From 18 HIV-1-positive spouse pairs, 12 very closely related pairs of sequences were identified. We conclude that there were multiple introductions of HIV-1 with limited spread, followed by explosive growth of a subtype C cluster, probably arising from a single introduction in or before 1983.
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    Efficacy of hepatitis A vaccination in children aged 12 to 24 months
    (2001) Abarca, K; Ibañez, I; Flores, J; Vial, PA; Safary, A; Potín, M
    Background. Current hepatitis A vaccines are either licensed for children >2 years of age. as in the U.S. or Chile, or >1 year of age, as in Europe and other parts of the world. Recent recommendations for immunization against hepatitis A have included routine vaccination of children in areas or regions of higher endemicity. However, data on hepatitis A vaccination in toddlers aged between 1 and 2 years are scarce.
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    Seroprevalence of parvovirus B19 in urban Chilean children and young adults, 1990 and 1996
    (2002) Abarca, K; Cohen, BJ; Vial, PA
    An immunofluorescence test for detecting parvovirus B19 IgG was developed by infecting insect cells with recombinant baculovirus expressing the capsid protein VP1. The test was used to study the prevalence of antibodies in 725 healthy children and young adults living in Santiago, Chile. In total, 248 sera were taken in 1990 and 477 in 1996. The seroprevalence was low in children less than 5 years old (3 % in 1990 and 21 % in 1996). It rose during school age to a prevalence around 50 %, reaching 60 % in young adults. No differences were found between genders. There was a statistically significant higher seroprevalence in the low socioeconomic status group in 1990 samples, but this was not observed in 1996. The higher prevalence observed in children less than 5 years of age in 1996 compared with 1990 could be explained by the occurrence of intervening epidemics of parvovirus B19 infection.