COVID-19, social determinants of transmission in the home. A population-based study.

BACKGROUND: Studying transmission within the home is essential to understand the transmission dynamics of numerous infectious diseases. For Coronavirus Disease-2019 (COVID-19), transmission within the home constitutes the majority exposure context. The risk of infection in this setting can be quantified by the household/intra-family secondary attack rate (SAR). In the literature, there are discrepancies in these values and little information about its social determinants. The aim of this study was to investigate transmission in the home by analyzing the influence of occupational social class, country of origin and gender/sex. METHODS: This was a retrospective cohort study of a population registry of cohabiting contacts with COVID-19 cases diagnosed from 15 June to 23 December 2020, in the Murcia Region. The household SAR was analyzed considering the characteristics of the primary case (sex, age, symptoms, occupational social class, country of origin and number of people in the household) and contact (age and sex) using a multilevel binary logistic regression model. RESULTS: Among the 37 727 contacts included, the intra-family SAR was 39.1%. The contacts of confirmed primary cases in the migrant population (Africa and Latin America) had higher attack rates, even after adjusting for the other variables. Older age and female sex were independent risk factors for contracting Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) within the home. CONCLUSION: There was greater intra-domiciliary transmission among immigrants, likely related to the conditions of the home and situation of social vulnerability. Women were more likely to be infected by transmission from a cohabiting infected individual.

Toenail zinc as a biomarker: Relationship with sources of environmental exposure and with genetic variability in MCC-Spain study.

BACKGROUND: Toenails are commonly used as biomarkers of exposure to zinc (Zn), but there is scarce information about their relationship with sources of exposure to Zn. OBJECTIVES: To investigate the main determinants of toenail Zn, including selected sources of environmental exposure to Zn and individual genetic variability in Zn metabolism. METHODS: We determined toenail Zn by inductively coupled plasma mass spectrometry in 3,448 general population controls from the MultiCase-Control study MCC-Spain. We assessed dietary and supplement Zn intake using food frequency questionnaires, residential proximity to Zn-emitting industries and residential topsoil Zn levels through interpolation methods. We constructed a polygenic score of genetic variability based on 81 single nucleotide polymorphisms in genes involved in Zn metabolism. Geometric mean ratios of toenail Zn across categories of each determinant were estimated from multivariate linear regression models on log-transformed toenail Zn. RESULTS: Geometric mean toenail Zn was 104.1 µg/g in men and 100.3 µg/g in women. Geometric mean toenail Zn levels were 7 % lower (95 % confidence interval 1-13 %) in men older than 69 years and those in the upper tertile of fibre intake, and 9 % higher (3-16 %) in smoking men. Women residing within 3 km from Zn-emitting industries had 4 % higher geometric mean toenail Zn levels (0-9 %). Dietary Zn intake and polygenic score were unrelated to toenail Zn. Overall, the available determinants only explained 9.3 % of toenail Zn variability in men and 4.8 % in women. DISCUSSION: Sociodemographic factors, lifestyle, diet, and environmental exposure explained little of the individual variability of toenail Zn in the study population. The available genetic variants related to Zn metabolism were not associated with toenail Zn.