FHM: Delta dominerar helt i Sverige om några månader

SARS-CoV-2 Delta variant, also known as lineage B.1.617.2, is a variant of lineage B.1.617 of SARS-CoV-2, the virus that causes COVID-19. It was first detected in India in late 2020. The World Health Organization (WHO) named it the Delta variant on 31 May 2021.It has mutations in the gene encoding the SARS-CoV-2 spike protein causing the substitutions T478K, P681R and L452R, which are known to affect transmissibility of the virus as well as whether it can be neutralised by antibodies for previously circulating variants of the COVID-19 virus. Public Health England (PHE) in May 2021 observed secondary attack rates to be 51–67% higher than the alpha variant. In a June technical briefing the Delta variant was linked to an increased risk in hospitalization.On 7 May 2021, PHE changed their classification of lineage B.1.617.2 from a variant under investigation (VUI) to a variant of concern (VOC) based on an assessment of transmissibility being at least equivalent to B.1.1.7 (Alpha variant), first identified in the UK (as the Kent variant). Subsequently on 11 May 2021, the WHO also classified this lineage VOC, and said that it showed evidence of higher transmissibility and reduced neutralisation. The variant is thought to be partly responsible for India's second wave of the pandemic beginning in February 2021. It later contributed to a third wave in the United Kingdom and South Africa, and the WHO warned in July 2021 it could have a similar effect elsewhere in Europe and Africa.On 7 June 2021, researchers at the National Centre for Infectious Diseases in Singapore posted a paper suggesting that patients testing positive for Delta are more likely to develop pneumonia and/or require oxygen than patients with wild type or Alpha. On 15 June 2021, the Center for Disease Control and Prevention declared Delta a variant of concern.On 25 June 2021, Public Health England issued Technical Briefing 17 on SARS-CoV-2 variants, documenting 32 deaths among 11,250 UK cases of SARS-CoV-2 Delta variant with 28 days follow-up with a fatality rate of 0.3%. This is similar to recent cases of the Alpha variant. These fatality rates are lower than the average fatality rate of 1.9%, presumably due to the now relative high percentage of the more vulnerable in England. However, the real issue is the relative growth rate of 0.93/week, resulting in a per week relative growth factor of exp(0.93)=2.5 with respect to the Alpha variant. This results, under the same infection prevention measures, in a much greater case load over time until a large fraction of people have been infected by it.