SARS-CoV-2 RNA and antibody dynamics in a Dutch household study with dense sampling frame

The performance of a lateral flow SARS-CoV-2 antibody assay and semi-autonomous SARS-CoV-2 antisense and sense RNA fluorescence in situ hybridization assay in a prospective cohort pilot study within a Dutch military population

At the beginning of the COVID-19 pandemic, diagnostic testing was not accessible for mildly ill or asymptomatic individuals. Military operational circumstances exclude the usage of reference laboratory tests. For that reason, at the beginning of the pandemic alternative test methods were needed in order to gain insight into the SARS-CoV-2 status of military personnel. The objectives of this study are to assess whether SARS-CoV-2 antibody rapid lateral flow assay (LFA) in combination with semi-autonomous SARS-CoV-2 antisense and sense genomic RNA fluorescence in situ hybridization (FISH) could establish disease status in military personnel in a fieldable setting, and to assess how this combination performed and to determine which type of sample performed best. A proof of concept sub-study regarding the SARS-CoV-2 application of the fieldable Biotrack-MED® FISH analyzer, a semi-autonomous multi-sample filter cytometer, preceded this observational prospective cohort pilot study. Dutch military personnel were included in the 26 June 2020-11 May 2021 period. Blood, nasopharyngeal and oropharyngeal swabs and saliva were tested at days 0 and 14. SPSS version 25 descriptive statistics and Cohen's kappa assessed agreement between test methods. Both the sensitivity and specificity of the field tests were calculated with ELISA and PCR as reference. Saliva appeared to be the preferred sample type for FISH, where blood was not useful. FISH analysis and LFA results had a concordance of 42% for testing negative, 30% for recovered from infection, 22% for ongoing-and 58% for acute infection in a reference laboratory lab result outcome (RT-PCR or ELISA respectively). The LFA results on serum and full blood corresponded with the ELISA-obtained results (kappa of 0.61 and 0.63 respectively at day 0 and 0.81 and 0.77 respectively at day 14). LFA (full blood-serum), FISH and RT-PCR on saliva did not reach the 90% sensitivity level advised by WHO, with 64-54, 38 and 71% at day 0 and 80-79, 53 and 24% at day 14 respectively.

The effect of variation of individual infectiousness on SARS-CoV-2 transmission in households

Quantifying variation of individual infectiousness is critical to inform disease control. Previous studies reported substantial heterogeneity in transmission of many infectious diseases including SARS-CoV-2. However, those results are difficult to interpret since the number of contacts is rarely considered in such approaches. Here, we analyze data from 17 SARS-CoV-2 household transmission studies conducted in periods dominated by ancestral strains, in which the number of contacts was known. By fitting individual-based household transmission models to these data, accounting for number of contacts and baseline transmission probabilities, the pooled estimate suggests that the 20% most infectious cases have 3.1-fold (95% confidence interval: 2.2- to 4.2-fold) higher infectiousness than average cases, which is consistent with the observed heterogeneity in viral shedding. Household data can inform the estimation of transmission heterogeneity, which is important for epidemic management.