Description: The Delta variant of SARS-CoV-2, the virus that causes Covid-19, has taken over the world, now accounting for 73% of global cases and rising. Around the world, from the UK to Indonesia to the US, Delta now dominates, making up 99% of the virus circulating in those countries. The US CDC, the WHO, and Public Health England are sounding the alarm on Delta. Why are epidemiologists alarmed about the Delta variant? Why are experts warning about Delta? In today’s video, I’m going to review the latest scientific literature to answer that question. In doing so, I’ll address five questions: (1) What is the delta variant? (2) Is delta more infectious or transmissible? (3) Does delta cause more severe illness or death? (4) Are vaccines less effective against delta? (5) And, how does delta change public health policy? It’s everything you need to know about Delta with evidence-based science explained! Shocking data from a leaked internal CDC report shows that breakthrough infections are not rare and that vaccinated individuals can harbor as much virus as unvaccinated people. The good news is that vaccines can still reduce the risk of hospitalizations and death, even against the delta variant. Covid is here to stay. New variants, including the lambda variant in Peru and a new variant called 21H in Colombia, are coming. We still need non-pharmaceutical interventions, including masks and limiting time in crowded indoor spaces. Finally, delta may cause countries like China, Australia, and New Zealand to abandon their Covid strategies. 0:00 Introduction 1:13 What is the Delta Variant? 3:42 Is the Delta Variant more transmissible? 5:55 Does the Delta Variant cause more severe disease? 7:52 Are vaccines effective against the Delta Variant? 11:21 What does this mean for public health policy? ****Links to studies and sources of data: SARS-CoV-2 variants of concern and variants under investigation in England, Public Health England Technical briefing 19 | https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1005517/Technical_Briefing_19.pdf SARS-CoV-2 Shared Mutations | https://covariants.org/shared-mutations Implications of the Novel Mutations in the SARS-CoV-2 Genome for Transmission, Disease Severity, and the Vaccine Development | https://doi.org/10.3389/fmed.2021.636532 Recent progress on the mutations of SARS-CoV-2 spike protein and suggestions for prevention and controlling of the pandemic | https://doi.org/10.1016/j.meegid.2021.104971 SARS-CoV-2 variants, spike mutations and immune escape | https://doi.org/10.1038/ s41579-021-00573-0 Clinical and Virological Features of SARS-CoV-2 Variants of Concern: A Retrospective Cohort Study Comparing B.1.1.7 (Alpha), B.1.315 (Beta), and B.1.617.2 (Delta) | https://doi.org/10.2139/ssrn.3861566 Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant | https://doi.org/10.1056/NEJMoa2108891 SARS-CoV-2 B.1.617.2 Delta variant emergence and vaccine breakthrough | https://doi.org/10.21203/rs.3.rs-637724/v1 Guidance for Implementing COVID-19 Prevention Strategies in the Context of Varying Community Transmission Levels and Vaccination Coverage | https://doi.org/10.15585/mmwr.mm7030e2 Effectiveness of COVID-19 vaccines against variants of concern in Ontario, Canada | https://doi.org/10.1101/2021.06.28.21259420 SARS-CoV-2 Delta VOC in Scotland: demographics, risk of hospital admission, and vaccine effectiveness | https://doi.org/10.1016/S0140-6736(21)01358-1 Progressive Increase in Virulence of Novel SARS-CoV-2 Variants in Ontario, Canada | https://doi.org/10.1101/2021.07.05.21260050 Outbreak of SARS-CoV-2 Infections, Including COVID-19 Vaccine Breakthrough Infections, Associated with Large Public Gatherings — Barnstable County, Massachusetts, July 2021 | http://dx.doi.org/10.15585/mmwr.mm7031e2