Pre-vaccination RT-PCR negative contacts in workplace settings show high, SARS COV-2 neutralizing antibody levels.

BACKGROUND: Asymptomatic SARS-CoV-2 infection occurring in RT-PCR negative individuals represent a poorly characterized cohort with important infection control connotations. While household and community-based studies have evaluated seroprevalence of antibody and transmission dynamics in this group, workplace-based data is currently unavailable. METHODS: A cohort study was carried out in July 2021, during and immediately following the peak of the 3rd wave of COVID-19 in Sri Lanka, prior to mass vaccination. A total of 92 unvaccinated individuals between the ages of 17-65 years were purposively sampled from an office and two factory settings. The selected cohort that had been exposed to RT-PCR positive cases in the workplace was tested RT-PCR negative. Serological samples collected six weeks post exposure were tested for anti-SARS-CoV-2 neutralizing antibody. RESULTS: The seroprevalence for SARS-CoV-2 specific neutralizing antibodies in the overall cohort was 63.04% (58/92). Seroprevalences in the office setting, factory setting 1 and factory setting 2 were 69.2% (9/13), 55.7% (34/61) and 83.33% (15/18), respectively. Primary risk factor associated with seropositivity was face to face contact with no mask for > 15 min (p < 0.024, Odds Ratio (OR); 5.58, 95%CI;1.292- 25.65). Individuals with workspace exposure had significantly higher levels of neutralizing antibodies than those who did not (percentage neutralization in assay 63.3% (SD:21)vs 45.7% (SD:20), p = 0.0042), as did individuals who engaged socially without protective measures (62.4 (SD:21.6)% vs 49.7 (SD:21)%, p = 0.026). CONCLUSION: There was a high seroprevalence for SARS-CoV-2 specific neutralizing antibodies among RT-PCR negative contacts in workplace settings in Sri Lanka. Higher levels of transmission of SARS-CoV-2 infection than estimated based on RT-PCR positive contact data indicate need for targeted infection control measures in these settings during future outbreaks.

Insight into genetic diversity of Mycobacterium tuberculosis in Kandy, Sri Lanka reveals predominance of the Euro-American lineage.

OBJECTIVE: Sri Lanka is a country where the molecular epidemiology of Mycobacterium tuberculosis (MTB) is poorly explored. Therefore, this study was performed to identify circulating lineages/sub-lineages of MTB and their transmission patterns. METHODS: DNA was extracted from 89 isolates of MTB collected during 2012 and 2013 from new pulmonary tuberculosis patients in Kandy, Sri Lanka and analyzed by spoligotyping, large sequence polymorphism (LSP), mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing, and drug resistance-associated gene sequencing. RESULTS: The predominant lineage was lineage 4 (Euro-American, 45.9%), followed by lineage 1 (Indo-Oceanic, 29.4%), lineage 2 (East-Asian, 23.5%), and lineage 3 (Central-Asian, 1.2%). Among 26 spoligotype patterns, eight were undesignated or new types and seven of these belonged to lineage 4. Undesignated lineage 4/SIT124 (n=2/8) and SIT3234 (n=8/8) clustered together based on 24-locus MIRU-VNTR typing. The dominant sub-lineage was Beijing/SIT1 (n=19), with the isoniazid resistance katG G944C mutation (Ser315Thr) detected in two of them. CONCLUSIONS: The population structure of MTB in Kandy, Sri Lanka was different from that in the South Asian region. The clonal expansion of locally evolved lineage 4/SIT3234 and detection of the pre-multidrug resistant Beijing isolates from new tuberculosis patients is alarming and will require continuous monitoring.

Leptospirosis outbreak in Sri Lanka in 2008: lessons for assessing the global burden of disease.

Global leptospirosis disease burden estimates are hampered by the lack of scientifically sound data from countries with probable high endemicity and limited diagnostic capacities. We describe the seroepidemiologic and clinical characteristics of the leptospirosis outbreak in 2008 in Sri Lanka. Definitive/presumptive case definitions proposed by the World Health Organization Leptospirosis Epidemiology Reference Group were used for case confirmation. Of the 404 possible cases, 155 were confirmed to have leptospirosis. Highest titers of patient seum samples reacted with serovars Pyrogenes (28.7%), Hardjo (18.8%), Javanica (11.5%), and Hebdomadis (11.5%). Sequencing of the 16S ribosomal DNA gene identified six infections: five with Leptospira interrogans and one with L. weilli. In this patient population, acute renal failure was the main complication (14.8%), followed by myocarditis (7.1%) and heart failure (3.9%). The case-fatality rate was 1.3%. This report strengthens the urgent need for increasing laboratory diagnostic capabilities to determine the causes of epidemic and endemic infectious diseases in Sri Lanka, a finding relevant to other tropical regions.