Comparative evaluation of a dual-target real-time RT-PCR assay for COVID-19 diagnosis and assessment of performance in pooled saliva and nasopharyngeal swab samples.

OBJECTIVES: Sensitive molecular diagnostic assays are essential for COVID-19 diagnosis. We evaluated the Hecin Scientific SARS-CoV-2 nucleic acid test kit, a dual-target real-time RT-PCR assay targeting the SARS-CoV-2 N and ORF1ab genes. METHODS: The Hecin test kit's diagnostic performance in detecting SARS-CoV-2 RNA was compared to the LightMix Modular SARS and Wuhan CoV E-gene kit (TIB Molbiol) and an in-house single-tube nested real-time RT-PCR using 296 clinical specimens, 11 proficiency testing samples, and 30 low-positive deep throat saliva and nasopharyngeal swab (NPS) samples pooled into negative samples in ratios of 1:5, 1:10, and 1:30. RESULTS: The limit-of-detection of the Hecin test kit was around 500 dC/mL for the N and ORF1ab targets. Sensitivity and specificity of the Hecin test kit were 98.1% (95% CI: 93.4-99.8%) and 100% (98.1-100%), respectively, when measured against the reference method. The Hecin test kit showed fair sensitivity (80%) in low-positive NPS samples pooled in ratios of 1:5 and 1:10. Its performance in pooled samples could be dramatically improved by adjusting the assay Ct cutoff. CONCLUSION: The Hecin test kit enables sensitive and specific detection of SARS-CoV-2 in clinical samples and pooled samples.

Assessment of population susceptibility to upcoming seasonal influenza epidemic strain using interepidemic emerging influenza virus strains.

Seasonal influenza virus epidemics have a major impact on healthcare systems. Data on population susceptibility to emerging influenza virus strains during the interepidemic period can guide planning for resource allocation of an upcoming influenza season. This study sought to assess the population susceptibility to representative emerging influenza virus strains collected during the interepidemic period. The microneutralisation antibody titers (MN titers) of a human serum panel against representative emerging influenza strains collected during the interepidemic period before the 2018/2019 winter influenza season (H1N1-inter and H3N2-inter) were compared with those against influenza strains representative of previous epidemics (H1N1-pre and H3N2-pre). A multifaceted approach, incorporating both genetic and antigenic data, was used in selecting these representative influenza virus strains for the MN assay. A significantly higher proportion of individuals had a ⩾four-fold reduction in MN titers between H1N1-inter and H1N1-pre than that between H3N2-inter and H3N2-pre (28.5% (127/445) vs. 4.9% (22/445), P < 0.001). The geometric mean titer (GMT) of H1N1-inter was significantly lower than that of H1N1-pre (381 (95% CI 339-428) vs. 713 (95% CI 641-792), P < 0.001), while there was no significant difference in the GMT between H3N2-inter and H3N2-pre. Since A(H1N1) predominated the 2018-2019 winter influenza epidemic, our results corroborated the epidemic subtype.

Population-Based Pediatric Hospitalization Burden of Lineage-Specific Influenza B in Hong Kong, 2004-2014.

BACKGROUND: Influenza B virus has been perceived to cause less disease burden and milder disease compared with influenza A, but recent studies suggest that influenza B does have a significant impact. We aimed to estimate the burden of influenza B virus infections on hospitalizations in Hong Kong, in the context of virus lineage changes over time. METHODS: The pediatric age-specific rates of influenza B hospitalization in Hong Kong for 2004-2014 were estimated based on admissions to 2 hospitals that together catered for 72.5% of all pediatric admissions on Hong Kong Island. Influenza B virus was detected by immunofluorescence and culture on nasopharyngeal aspirates. Lineage typing was performed by real-time reverse-transcription polymerase chain reaction. RESULTS: A total of 5085 children were recruited on 1 designated day each week, year-round during the 11 years, and 221 (4.3%) tested positive for influenza B. Hospitalization rates were highest in children aged 2 to <5 years with year-to-year variation. Victoria-lineage viruses appeared to be associated with a greater fraction of influenza B hospitalizations in children than of influenza B infections in the general community. Influenza B did not cause significant hospitalization in infants <1 year of age. CONCLUSIONS: We report one of the first population-based, age- and lineage-specific studies of pediatric hospitalization for influenza B. We found that changes in lineage were associated with higher hospitalization rates and documented that Victoria lineage viruses were associated with greater pediatric hospitalization burden compared with Yamagata lineage viruses.

A robust parameter estimation method for estimating disease burden of respiratory viruses.

BACKGROUND: Poisson model has been widely applied to estimate the disease burden of influenza, but there has been little success in providing reliable estimates for other respiratory viruses. METHODS: We compared the estimates of excess hospitalization rates derived from the Poisson models with different combinations of inference methods and virus proxies respectively, with the aim to determine the optimal modeling approach. These models were validated by comparing the estimates of excess hospitalization attributable to respiratory viruses with the observed rates of laboratory confirmed paediatric hospitalization for acute respiratory infections obtained from a population based study. RESULTS: The Bayesian inference method generally outperformed the classical likelihood estimation, particularly for RSV and parainfluenza, in terms of providing estimates closer to the observed hospitalization rates. Compared to the other proxy variables, age-specific positive counts provided better estimates for influenza, RSV and parainfluenza, regardless of inference methods. The Bayesian inference combined with age-specific positive counts also provided valid and reliable estimates for excess hospitalization associated with multiple respiratory viruses in both the 2009 H1N1 pandemic and interpandemic period. CONCLUSIONS: Poisson models using the Bayesian inference method and virus proxies of age-specific positive counts should be considered in disease burden studies on multiple respiratory viruses.

The population based socioeconomic burden of pediatric influenza-associated hospitalization in Hong Kong.

We described the monetary and non-monetary cost incurred by children hospitalized for virologically confirmed influenza virus infection in a population-based prospective 3-year study. The mean direct and indirect cost of each child hospitalized was $1217.82 (95% CI, 1111.54-1324.23) and $1328.33 (95% CI, $1136.79-1520.00) for influenza A and B, respectively. School age patients took a mean (SD) of 4.70 (3.05) days and 5.31 (3.62) days of sick leave for influenza A and B infection, respectively. Pediatric influenza A and B hospitalization was associated with 662-1046 days of school absenteeism and 214-336 days of parental work loss per 10,000 population <18 years of age per year. We showed that the cost incurred by hospitalization alone, was comparable to the cost of annual universal pediatric influenza vaccination especially in children 6 months to under 6 years of age and vaccination would result in much larger cost-savings when non-monetary costs are included.