Regional epidemic dynamics and Delta variant diversity resulted in varying rates of spread of Omicron-BA.1 in Mexico

The Omicron subvariant BA.1 of SARS-CoV-2 was first detected in November 2021 and quickly spread worldwide, displacing the Delta variant. In Mexico, this subvariant began spreading during the first week of December 2021 and became dominant in the next three weeks, causing the fourth COVID-19 epidemiological surge in the country. Unlike previous SARS-CoV-2 variants, BA.1 did not acquire local substitutions nor exhibited a geographically distinct circulation pattern in Mexico. However, a regional difference in the speed of the replacement of the Delta variant was observed, as some northern states showed persistence of Delta lineages well into February 2022. Mexican states were divided into four regions (North, Central North, Central South, and Southeast) based on the lineage circulation before the dominance of BA.1 to study possible causes for this difference. For each region, the time to fixation of BA.1, the diversity of Delta sublineages in the weeks preceding BA.1 entry, the population density, and the level of virus circulation during the inter-wave interval were determined. An association between a faster Omicron spread and lower Delta diversity, as well as fewer COVID-19 cases during the Delta-BA.1.x inter-wave period, was observed. For example, the North region exhibited the slowest spread but had the highest diversity of Delta sublineages and the greatest number of inter-wave cases relative to the maximum amount of the virus circulating in the region, whereas the Southeast region showed the opposite. Viral diversity and the relative abundance of the virus in a particular area around the time of the introduction of a new lineage seem to have influenced the spread dynamics. Nonetheless, if there is a significant difference in the fitness of the variants or the time allowed for the competition is sufficient, it seems the fitter virus will eventually become dominant, as observed in the eventual dominance of the BA.1.x variant in Mexico. Impact statementThe surveillance of lineage circulation of SARS-CoV-2 has helped identify variants that have a transmission advantage and are of concern to public health and to track the virus dispersion accurately. However, many factors contributing to differences in lineage spread dynamics beyond the acquisition of specific mutations remain poorly understood. In this work, a description of BA.1 entry and dispersion within Mexico is presented, and which factors potentially affected the spread rates of the Omicron variant BA.1 among geographical regions in the country are analyzed, underlining the importance of population density, the proportion of active cases, and viral lineage diversity and identity before the entry of BA.1. Data summaryThis work was carried out using data shared through the GISAID initiative. All sequences and metadate are available through GISAID with the accession EPI_SET_220927gw, accession numbers and metadata are also reported in the supplemental material of this article. Epidemiological data was obtained though the Secretaria de Salud website (https://www.gob.mx/salud/documentos/datos-abiertos-152127),

Maternal and neonatal risk factors associated with increased mother-to-child transmission of HIV-1 in Mexico: Results of a case-control study.

BACKGROUND: Maternal, obstetric and neonatal factors that increase the possibility of mother-to-child HIV transmission (MTCT) are known as mechanisms of transmission. Our aim was to determine the risk factors associated with MTCT in Mexico. METHODS: We conducted a case-control study from March to December 2015. Cases were 60 mothers with HIV infection who transmitted HIV to their children, and controls were 120 mothers with HIV infection whose children tested negative for HIV. Data were extracted from medical records and a self-reported questionnaire for each participant. To determine associations with MTCT, odds ratios (ORs) and 95% confidence intervals (CI) were obtained with the chi-squared test and a logistic-regression modeling. RESULTS: A total of 180 patients were included. HIV diagnosis for cases occurred after pregnancy in 88% of the patients, during pregnancy in 9%, and before pregnancy in 3% of patients. Among the controls, 38% of patients were diagnosed before pregnancy, 32% during pregnancy, and 30% after pregnancy. In multivariate analysis, the risk factors associated with MTCT were: absence of antiretroviral treatment during pregnancy (OR 5.21; 95% CI 1.24-16.11; p = 0.019); vaginal delivery (OR 3.2; 95% CI 1.27-8.26; p = 0.014); forceps-assisted delivery (OR 13.4; 95% CI 1.91-93.66; p = 0.009); breastfeeding (OR 6.23; 95% CI 2.27-17.05; p = <0.001) and the practice of mixed breastfeeding (OR 4.6; 95% CI 1.56-13.73; p = 0.006). CONCLUSIONS: MTCT is preventable with early diagnosis; treatment initiation before pregnancy and avoidance breastfeeding could decrease the risk of transmitting HIV to their children.

Weak association of coinfection by SARS-CoV-2 and other respiratory viruses with severe cases and death

BackgroundSARS-CoV-2 is a novel coronavirus described for the first time in China in December 2019. This virus can cause a disease that ranges in spectrum from asymptomatic to severe respiratory disease with multiorgan failure, and the most severe cases are associated with some comorbidities and patient age. However, there are patients who do not have those risk factors who still develop serious disease. MethodsIn this study, we identified the presence of other respiratory viruses in positive cases of COVID-19 in Mexico to determine if any coinfections were correlated with more severe manifestations of COVID-19. We analysed 103 confirmed cases of COVID-19 using RT-qPCR for the detection of 16 other respiratory viruses. ResultsOf the cases analysed, 14 (13.6%) were cases of coinfection, and 92% of them never required hospitalization, even when comorbidities and advanced age were involved. There werent significant differences between the presence of comorbidities and the mean ages of the groups ConclusionsThese results suggest that coinfection is not related to more severe COVID-19 and that, depending on the virus involved, it could even lead to a better prognosis. We believe that our findings may lay the groundwork for new studies aimed at determining the biological mechanism by which this phenomenon occurs and for proposing corresponding strategies to limit the progression to severe cases of COVID-19. CLINICAL TRIAL REGISTRATIONNot apply