Occurrence of influenza B/Hong Kong-Like strains in Brazil, during 2002

Abstract

Through the influenza virus surveillance from January to October 2002, influenza B/Hong Kong-like strains circulating in the Southeast and Centre East regions of Brazil have been demonstrated. This strain is a variant from B/Victoria/02/88 whose since 1991 and until recently have been isolated relatively infrequently and have been limited to South-Eastern Asia. A total of 510 respiratory secretions were collected from patients 0 to 60 years of age, with acute respiratory illness, living in the Southeast and Centre East regions of Brazil, of which 86 (17.13%) were positive for influenza virus. Among them 12 (13.95%) were characterized as B/Hong Kong/330/2001; 3 (3.49%) as B/Hong Kong/1351/2002 a variant from B/Hong Kong/330/2001; 1 (1.16%) as B/Sichuan/379/99; 1 (1.16%) as B/Shizuoka/5/2001, until now. The percentages of cases notified during the surveillance period were 34.88%, 15.12%, 15.12%, 4.65%, 15.12%, 13.95%, in the age groups of 0-4, 5-10, 11-15, 16-20, 21-30, 31-50, respectively. The highest proportion of isolates was observed among children younger than 4 years but serious morbidity and mortality has not been observed among people older than 65 years, although B influenza virus component for vaccination campaign 2002 was B/Sichuan/379/99 strain. This was probably due to the elderly protection acquired against B/Victoria/02/88. In addition, in influenza A/Panama/2007/99-like (H3N2) strains 22 (25.58%) were also detected, but influenza A(H1N1) has not been detected yet.A vigilância do vírus da influenza, no periodo de janeiro a outubro de 2002, detectou a circulação da estirpe B/Hong Kong/330/2001 nas regiões Sudeste e Centro Oeste do país. Esta estirpe é uma variante do vírus da influenza B/Victoria/02/88 a qual teve sua circulação circunscrita no continente asiático por volta de 1991. Variantes da estirpe B/Hong Kong/330/2001 (B/Hong Kong/1351/2002) e da estirpe B/Sichuan/379/99 (B/Shizuoka/5/2001) também foram detectadas. A porcentagem de vírus caracterizados durante a epidemia foi de 34,88%, 15,12%, 15,12%, 4,65%, 15,12%, 13,95%, nas faixas etárias de 0-4, 5-10, 11-15, 16-20, 21-30, 31-50, respectivamente. Observou-se maior incidência da doença entre os indivíduos menores de 4 anos. Atribuiu-se a ausência de notificação nos indivíduos maiores de 60 anos ao contato prévio, desta faixa etária, com o vírus na década de 80. No mesmo período, detectou-se a circulação do vírus da influenza A/Panamá/2007/99-like (H3N2), por outro lado evidenciou-se a ausência da circulação da estirpe A(H1N1) até a presente data