We aimed to test the sensitivity of naso-oropharyngeal saliva and self-administered nasal (SN) swab compared to nasopharyngeal (NP) swab for COVID-19 testing in a large cohort of migrant workers in Singapore. We also tested the utility of next-generation sequencing (NGS) for diagnosis of COVID-19. Saliva, NP and SN swabs were collected from subjects who presented with acute respiratory infection, their asymptomatic roommates, and prior confirmed cases who were undergoing isolation at a community care facility in June 2020. All samples were tested using RT-PCR. SARS-CoV-2 amplicon-based NGS with phylogenetic analysis was done for 30 samples. We recruited 200 subjects, of which 91 and 46 were tested twice and thrice respectively. In total, 62.0%, 44.5%, and 37.7% of saliva, NP and SN samples were positive. Cycle threshold (Ct) values were lower during the earlier period of infection across all sample types. The percentage of test-positive saliva was higher than NP and SN swabs. We found a strong correlation between viral genome coverage by NGS and Ct values for SARS-CoV-2. Phylogenetic analyses revealed Clade O and lineage B.6 known to be circulating in Singapore. We found saliva to be a sensitive and viable sample for COVID-19 diagnosis.

BackgroundPanax notoginseng is a potential source of anticancer compounds. This study aims to investigate the effects of steaming on the chemical profile of P. notoginseng and the anti-proliferative effects of P. notoginseng on liver cancer cells.MethodsSamples of powdered raw P. notoginseng roots were steamed for various durations. Extracts of the raw and steamed samples were subjected to ultra-high pressure liquid chromatography/mass spectrometry (UHPLC-MS) analysis for chemical profiling. The anti-proliferative effects on three human liver cancer cells, namely SNU449, SNU182 and HepG2, were evaluated using colorimetric WST-1 assay.ResultsSteaming changed chromatographic and pharmacological profiles of P. notoginseng, causing differences in activities such as inhibition of cancer growth. Steamed P. notoginseng exhibited greater anti-proliferative effects against liver cancer cells (SNU449, SNU182 and HepG2) than its raw form; steaming up to 24 hours increased bioactivities. Steaming increased the concentrations of ginsenoside Rh2, Rk1, Rk3 and 20S-Rg3 and enhanced growth inhibition of liver cancer cells.ConclusionSteaming changes the chemical profile as well as anti-cancer biological activities of P. notoginseng. Steamed P. notoginseng contains potential compounds for the treatment of liver cancer.

ObjectivesTo develop a localised instrument and Bayesian statistical method to generate size estimates—adjusted for transmission error and barrier effects—of at-risk populations in Singapore.MethodsWe conducted indepth interviews and focus group to guide the development of the survey questionnaire. The questionnaire was administered between July and August 2017 in Singapore. Using the network scale-up method (NSUM), we developed a Bayesian hierarchical model to estimate the number of individuals in four hidden populations at risk of HIV. The method accounted for both transmission error and barrier effects using social acceptance measures and demographics.ResultsThe adjusted size estimate of the population of male clients of female sex workers was 72 000 (95% CI 51 000 to 100 000), of female sex workers 4200 (95% CI 1600 to 10 000), of men who have sex with men 210 000 (95% CI 140 000 to 300 000) and of intravenous drug users 11 000 (95% CI 6500 to 17 000).ConclusionsThe NSUM with adjustment for attitudes and demographics allows national-level estimates of multiple priority populations to be determined from simple surveys of the general population, even in relatively conservative societies.