Background: Prevalence estimates for celiac disease (CD) depend on the method used. The role of deamidated gliadin peptide (DGP) and genetic testing in epidemiological studies and diagnostic settings of celiac disease (CD) has still to be established. Objectives: The objective of this article is to assess the prevalence of CD in Latvia by combining serological tests with DQ2.5/ DQ8 testing. Methods: A total of 1444 adults from a randomly selected cross-sectional general population sample were tested by ELISA for tTG IgA, DGP IgA and IgG antibodies (QUANTA Lite Õ , Inova Diagnostics Inc). Samples with tTG IgA !20U were tested for EMA IgA by indirect immunofluorescence assay, and all specimens with tTG IgA !15U were tested by QUANTA-Flash Õ chemiluminescent assays (CIA) (Inova Diagnostics Inc) for tTG IgA, DGP IgA and IgG. DQ2.5/8 was detected in individuals with any positive ELISA test and a subgroup of controls. Results: Forty-three individuals (2.98%; 95% CI: 2.10-3.86%) tested positive by at least one ELISA test; 41.86% of the serology-positive individuals (any test above the cutoff) were DQ positive. Six individuals (0.42%; 95% CI: 0.09-0.75%) were triple ELISA positive, and DQ2.5 or DQ8 was positive in all; 0.35% (95% CI: 0.05-0.65%) were tTG IgA and EMA positive. Two tTG IgA-negative cases were both DGP IgG and IgA positive, both being DQ positive; including them in the ''serologypositive'' group would increase the prevalence to 0.49% (95% CI: 0.13-0.85%). CIA tests revealed 2 tTG IgA-positive and EMA-negative cases with a positive genotype. DQ2.5 or DQ8 genotype was positive in 28.6% of the serology-negative population. Conclusions: Estimates of the prevalence of CD in Latvia based on the serogenetic testing approach range from 0.35% to 0.49% depending on the criteria used. There is a rationale for combining serological tests and DQ2.5/8 genotyping.

Remaining a major healthcare concern with nearly 29 million confirmed cases worldwide at the time of writing, novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused more than 920 thousand deaths since its outbreak in China, December 2019. First case of a person testing positive for SARS-CoV-2 infection within the territory of the Republic of Latvia was registered on 2nd of March 2020, 9 days prior to the pandemic declaration by WHO. Since then, more than 277,000 tests were carried out confirming a total of 1,464 cases of coronavirus disease 2019 (COVID-19) in the country as of 12th of September 2020. Rapidly reacting to the spread of the infection, an ongoing sequencing campaign was started mid-March in collaboration with the local testing laboratories, with an ultimate goal in sequencing as much local viral isolates as possible, resulting in first full-length SARS-CoV-2 isolate genome sequences from the Baltics region being made publicly available in early April. With 133 viral isolates representing ~9.1% of the total COVID-19 cases during the “first coronavirus wave” in the country (early March, 2020—mid-September, 2020) being completely sequenced as of today, here, we provide a first report on the genetic diversity of Latvian SARS-CoV-2 isolates.

There is an urgency for the rapid and simple SARS-CoV-2 detection method. Our study aimed to demonstrate that saliva can be used as a specimen for SARS-CoV-2 detection notably for the screening of extensive population groups via pooling. We collected paired nasopharyngeal/oropharyngeal swabs (NPS) and saliva and performed 36 serial measurements of 8 SARS-CoV-2 positive saliva samples to confirm the stability of the specimen. We also completed 37 pools by adding one positive saliva specimen per pool. A field study including 3,660 participants was performed between September 29 and October 1, 2020. Saliva specimens were stable for testing for up to 24 hours. Overall, 1.2% of the saliva samples tested positive for SARS-CoV-2. The results of saliva samples were consistent with those obtained from NPS with 90% sensitivity (95% CI 68.3%-98.7%) and 100% specificity during the first two weeks after the onset of symptoms. All pools showed 100% positivity in different pooling proportions. Our findings demonstrate that saliva is an appropriate specimen for pooling and SARS-CoV-2 screening with accurate diagnostic performance. Patient-performed specimen collection allows testing an extensive number of people rapidly, obtaining results of the spread of SARS-CoV-2 and allowing authorities to take timely measures.

Remaining a major healthcare concern with nearly 27 million confirmed cases worldwide at the time of writing, novel severe acute respiratory syndrome coronavirus - 2 (SARS-CoV-2) has caused more than 880 thousand deaths since its outbreak in China, December 2019. First case of a person testing positive for SARS-CoV-2 infection within the territory of the Republic of Latvia was registered on 2nd of March 2020, nine days prior to the pandemic declaration by WHO. Since then, more than 230 000 tests were carried out confirming a total of 1330 cases of COVID-19 in the country as of 20th of August 2020. Rapidly reacting to the spread of the infection, an ongoing sequencing campaign was started mid-March in collaboration with the local testing laboratories, with an ultimate goal in sequencing as much local viral isolates as possible, resulting in first full-length SARS-CoV-2 isolate genome sequences from the Baltics region being made publicly available in early April. With 109 viral isolates representing ~8.2% of the total COVID-19 cases in the country being completely sequenced as of today, here we provide a first report on the genetic diversity of Latvian SARS-CoV-2 isolates.

The aim of our study was to demonstrate that saliva can be used as an effective material for SARS-CoV-2 testing and screening of large population groups to identify Covid-19 clusters. The most important aspect of saliva sampling approach is the convenience of obtaining material by self- sampling that is even possible at home. In our experiments, saliva was sufficiently stable for testing for at least 24 hours after collection. The results obtained from the saliva of a SARS-CoV-2 positive patient were consistent with those obtained from nasopharyngeal and oropharyngeal swabs from the same patient with the sensitivity 90% and specificity 100% during the first two weeks after the onset of symptoms. To demonstrate the usefulness of testing saliva material for mass screening, crowd sampling with pooling was performed on 3660 people in 3-day time (44 samples were tested positive). We conclude that saliva testing is an appropriate tool for screening campaigns and cluster detection, that is able to detect more infected people in a shorter period of time with little human resources and thus help to stop the epidemic spread more quickly.