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ABSTRACT: Understanding household transmission of the pandemic influenza A(H1N1)2009 virus, including risk factors for transmission, is important for refining public health strategies to reduce the burden of the disease. During the influenza season of 2009 we investigated transmission of the emerging virus in 595 households in which the index case was the first symptomatic case of influenza A(H1N1)2009. Secondary cases were defined as household contacts with influenza-like illness (ILI) or laboratory-confirmed influenza A(H1N1)2009, occurring at least one day after but within seven days following symptom onset in the index case. ILI developed in 231 of the 1,589 household contacts, a secondary attack rate of 14.5% (95% confidence interval (CI): 12.9–16.4). At least one secondary case occurred in 166 of the 595 households (a household transmission rate of 27.9%; 95% CI: 24.5–31.6).Of these, 127 (76.5%) households reported one secondary case and 39 (23.5%) households reported two or more secondary cases. Secondary attack rates were highest in children younger than five years (p=0.001), and young children were also more efficient transmitters (p=0.01). Individual risk was not associated with household size. Prophylactic antiviral therapy was associated with reduced transmission (p=0.03). The secondary attack rate of ILI in households with a confirmed pandemic influenza A(H1N1)2009 index case was comparable to that described previously for seasonal influenza.
Euro surveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 01/2011; 16(3). · 6.15 Impact Factor
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ABSTRACT: Dengue epidemic virulence is thought to be conferred by various factors, including the genotype of the virus involved. Increased or decreased epidemic virulence has been associated not only with the introduction of type-2 (DENV-2) strains into the South Pacific, the Caribbean and South America, but also with newly emergent DENV-3 genotypes in Sri Lanka, and the year-to-year variation in the DENV-4 strains circulating in Puerto Rico. These observations indicate that there are inherent differences among viral genotypes in their capacity to induce severe disease, that is, their virulence potential. The present study involved a comparison of the complete genome sequences of DENV-1 viruses that had been isolated from cases of dengue fever (DF) or dengue haemorrhagic fever (DHF) that occurred in French Polynesia or Hawaii in 2001, when a virulent DHF-associated dengue epidemic was occurring throughout the Pacific region. Previous studies have identified putative virulence-associated motifs and substitutions in the DENV-2 genome, and the main aim of the present study was to identify similar changes in DENV-1 that may be associated with viral virulence. As no virulence determinants were seen, however, in any gene or untranslated region, it appears that genotype is not the sole determinant of virulence in DENV-1. Further studies, to compare DF- and DHF-associated strains of DENV-1 isolated from epidemics of variable virulence, in the same eco-biological context, are needed.
Annals of Tropical Medicine and Parasitology 04/2010; 104(3):225-35. · 1.43 Impact Factor
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ABSTRACT: We conducted a prospective household transmission study to examine whether receipt of 2009 trivalent influenza vaccine (TIV) was associated with increased risk of influenza-like illness (ILI) among contacts of confirmed pandemic influenza A(H1N1) 2009 patients. In the week following onset of pandemic illness in a household member, 46 (15%) of 304 TIV-vaccinated contacts, and 174 (15%) of 1,162 unvaccinated contacts developed ILI (p=0.95). Receipt of 2009 TIV had no effect on one's risk of pandemic illness.
Euro surveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 01/2010; 15(28). · 6.15 Impact Factor
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ABSTRACT: Australian and New Zealand health authorities identified seasonal trivalent inactivated influenza vaccines manufactured by CSL Biotherapies as the probable cause of increased febrile convulsions in children under five within 24 hours of vaccination and recommended against their use in this age group. We quantified the benefit-risk profile of the CSL vaccines using the number needed to vaccinate and suggest they might have caused two to three hospital admissions due to febrile convulsions for every hospital admission due to influenza prevented.
Euro surveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 01/2010; 15(37). · 6.15 Impact Factor
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Euro surveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 01/2010; 15(40). · 6.15 Impact Factor
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ABSTRACT: In 2000, a major dengue epidemic, caused by the type-1 virus (DENV-1), began in the Pacific and Asia, with cases still being reported in 2006. The phylogenetic analysis of full-length sequences of the envelope-protein gene of DENV-1 isolates recovered during outbreaks in Hawaii and Tahiti in 2001-2002 indicated that most Hawaiian isolates were Tahitian in origin. All the Hawaiian and Tahitian isolates were identified as the Pacific subtype (i.e. subtype IV) of DENV-1. A Hawaiian isolate, collected from a resident who had travelled to Samoa, differed significantly at the nucleotide level, however, from all the other Hawaiian strains, clustering, in the phylogenetic analysis, with a virus previously isolated from another visitor to Samoa. These results not only indicate that two distinct strains of DENV-1 were introduced into Hawaii in 2001 but also illustrate the ease with which dengue can be carried across distances of many thousands of miles.
Annals of Tropical Medicine and Parasitology 07/2006; 100(4):327-36. · 1.43 Impact Factor
