ABSTRACT
The complete genomes of three human H5N1 influenza isolates were characterized, together with the haemagglutinin (HA) and neuraminidase (NA) genes from two additional human isolates and one chicken isolate. These six influenza isolates were obtained from four different provinces of Thailand during the avian influenza outbreak in Asia from late 2003 to May 2004. All six Thailand isolates contained multiple basic amino acids at the cleavage site in the HA gene. Amino acid residues at the receptor-binding site of the five human viruses were similar to those of the chicken virus and other H5N1 viruses from Hong Kong. The presence of amantadine resistance in the Thailand viruses isolated during this outbreak was suggested by a fixed mutation in M2 and confirmed by a phenotypic assay. All genomic segments of the Thailand viruses clustered with the recently described genotype Z. The Thailand viruses contained more avian-specific residues than the 1997 Hong Kong H5N1 viruses, suggesting that the virus may have adapted to allow a more efficient spread in avian species.
Subject(s)
Disease Outbreaks , Influenza A Virus, H5N1 Subtype , Influenza A virus/genetics , Influenza, Human/epidemiology , RNA, Viral/genetics , Amantadine/pharmacology , Animals , Antiviral Agents/pharmacology , Chickens/virology , Drug Resistance, Viral , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Humans , Influenza A virus/drug effects , Influenza A virus/isolation & purification , Influenza in Birds/epidemiology , Influenza, Human/virology , Molecular Epidemiology , Molecular Sequence Data , Mutation , Neuraminidase/genetics , Phylogeny , Receptors, Virus , Sequence Alignment , Species Specificity , Thailand/epidemiology , Viral Matrix Proteins/geneticsABSTRACT
In Thailand, the morbidity rate of measles has declined since measles vaccination was included in the National Immunization Programme. A measles outbreak affected 41 infants in an orphanage in Bangkok during September-October 2000 prompted an investigation to study the epidemiological distribution, assess vaccine coverage and vaccine effectiveness. The attack rate was 66 per cent, among infants aged 6-12 months in two separate rooms. Sixty-three per cent of the 41 cases were less than 9 months old. Measles vaccine coverage among infants over 9 months was 45 per cent due to delay in immunization caused by mild illnesses of the infants and the vaccine effectiveness was 91 per cent (95%CI 42%-99%). Inefficiency of the surveillance system to early detect and respond to the outbreak was observed. A catch-up immunization program, close supervision for surveillance and immunization systems and an increase of measles vaccine coverage to more than 95 per cent in this and other orphanages in Thailand were recommended.
