ABSTRACT
Reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) is a unique gene amplification method that can be completed within 35 min at 62.5 degrees C. In the present study, RT-LAMP was used to develop a rapid and sensitive laboratory diagnostic system for the H5N1 highly pathogenic avian influenza (HPAI). The sensitivity of the system was 0.1-0.01 plaque-forming units per reaction for HPAI-H5N1 viruses belonging to the genetically and antigenically distinct clade 1, represented by A/Vietnam/JP1203/2004, and clade 2, represented by A/Indonesia/JP283/2006. This RT-LAMP sensitivity is 10-fold higher than the sensitivity of standard one-step RT-PCR. By using viral RNAs extracted from avian influenza viruses of H1-H15 hemagglutinin (HA) subtypes and human pathogenic respiratory viruses, it was confirmed that the RT-LAMP system amplifies specifically RNA of the H5 subtype virus. The system detected H5-HA genes in throat swabs collected from humans as well as from wild birds. These results suggest that the present RT-LAMP system is a useful diagnostic tool for surveillance of recent outbreaks of the HPAI-H5N1 virus.
Subject(s)
Influenza A Virus, H5N1 Subtype/isolation & purification , Influenza A virus/isolation & purification , Influenza in Birds/diagnosis , Influenza, Human/diagnosis , Reverse Transcriptase Polymerase Chain Reaction/methods , Adolescent , Adult , Aged , Animals , Antigens, Viral/genetics , Base Sequence , Child , Child, Preschool , Crows , DNA Primers/genetics , Genes, Viral , Hemagglutinin Glycoproteins, Influenza Virus/genetics , Humans , Influenza A Virus, H5N1 Subtype/genetics , Influenza A virus/genetics , Influenza in Birds/virology , Influenza, Human/virology , Middle Aged , Molecular Sequence Data , Sensitivity and Specificity , Species SpecificityABSTRACT
During 2005, 764 children were brought to a large children's hospital in Ho Chi Minh City, Vietnam, with a diagnosis of hand, foot, and mouth disease. All enrolled children had specimens (vesicle fluid, stool, throat swab) collected for enterovirus isolation by cell culture. An enterovirus was isolated from 411 (53.8%) of the specimens: 173 (42.1%) isolates were identified as human enterovirus 71 (HEV71) and 214 (52.1%) as coxsackievirus A16. Of the identified HEV71 infections, 51 (29.5%) were complicated by acute neurologic disease and 3 (1.7%) were fatal. HEV71 was isolated throughout the year, with a period of higher prevalence in October-November. Phylogenetic analysis of 23 HEV71 isolates showed that during the first half of 2005, viruses belonging to 3 subgenogroups, C1, C4, and a previously undescribed subgenogroup, C5, cocirculated in southern Vietnam. In the second half of the year, viruses belonging to subgenogroup C5 predominated during a period of higher HEV71 activity.
Subject(s)
Hand, Foot and Mouth Disease/epidemiology , Hand, Foot and Mouth Disease/virology , Adolescent , Animals , Capsid Proteins/genetics , Cell Line, Tumor , Child , Chlorocebus aethiops , Enterovirus A, Human/genetics , Enterovirus A, Human/isolation & purification , Hand, Foot and Mouth Disease/transmission , Humans , Phylogeny , Reverse Transcriptase Polymerase Chain Reaction/methods , Vero Cells , Vietnam/epidemiologyABSTRACT
To evaluate risk factors for human infection with influenza A subtype H5N1, we performed a matched case-control study in Vietnam. We enrolled 28 case-patients who had laboratory-confirmed H5N1 infection during 2004 and 106 age-, sex-, and location-matched control-respondents. Data were analyzed by matched-pair analysis and multivariate conditional logistic regression. Factors that were independently associated with H5N1 infection were preparing sick or dead poultry for consumption < or =7 days before illness onset (matched odds ratio [OR] 8.99, 95% confidence interval [CI] 0.98-81.99, p = 0.05), having sick or dead poultry in the household < or =7 days before illness onset (matched OR 4.94, 95% CI 1.21-20.20, p = 0.03), and lack of an indoor water source (matched OR 6.46, 95% CI 1.20-34.81, p = 0.03). Factors not significantly associated with infection were raising healthy poultry, preparing healthy poultry for consumption, and exposure to persons with an acute respiratory illness.
Subject(s)
Influenza A Virus, H5N1 Subtype/growth & development , Influenza, Human/virology , Adolescent , Adult , Animals , Case-Control Studies , Child , Child, Preschool , Female , Humans , Infant , Influenza, Human/epidemiology , Influenza, Human/transmission , Logistic Models , Male , Poultry , Poultry Diseases/virology , Risk Factors , Surveys and Questionnaires , Vietnam/epidemiology , Zoonoses/transmission , Zoonoses/virologyABSTRACT
For 5 years, we have conducted sentinel surveillance for rotavirus at 6 hospitals in 4 cities in Vietnam. Stool samples obtained from >10,000 children <5 years old who were admitted to the hospital with diarrhea have been screened for rotavirus. Overall, 55% of samples were positive, and there was little variability in rates of detection of rotavirus between sites (44%-62%). In Vietnam, the characteristics of rotavirus infection more closely resemble those seen in developed countries, rather than those seen in developing countries: children become infected at an older age, the percentage of stool samples in which rotavirus is detected is extremely high, and the rotavirus strains appear to be the common types, with fewer mixed infections occurring. It is estimated that 5300-6800 children <5 years old die of rotavirus infection each year in Vietnam, representing 8%-11% of all deaths in this age group (cumulative risk per child by age 5 years, 1 in 200 to 1 in 285). Additional studies are ongoing to document the economic cost of the disease and to assess the burden of both fatal cases and milder cases of disease. Study outcomes will provide information for future testing and potential use of a rotavirus vaccine.
