USA extends border restrictions with Canada until Sept. 21

CBC News shows that the USA Department of Homeland Security said that the delta variant and case counts are the reasons for keeping the country's land border closed.

The so-called SARS-CoV-2 Delta variant, also known as lineage B.1.617.2, or "Indian variant" 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.

The virus variant 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. In August 2021, Public Health England (PHE) reported secondary attack rate in household contacts of non-travel or unknown cases for Delta to be 10.8% versus 10.2% for the alpha variant; the case fatality rate for those 300,010 with Delta is 0.2%, where half of the cases and one third of the deaths are unvaccinated. COVID-19 vaccines are effective in preventing severe disease or hospitalisation from infection with the dangerous virus variant.

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); the UK's SAGE subsequently estimated a "realistic" possibility of being 50% more transmissible. On 11 May 2021, the WHO also classified this lineage VOC, and said that it showed evidence of higher transmissibility and reduced neutralisation. On 15 June 2021, the Centers for Disease Control and Prevention (CDC) declared Delta a variant of concern.

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 Fiji, the United Kingdom and South Africa, and the WHO warned in July 2021 that it could have a similar effect elsewhere in Europe and Africa. By late July it had also driven an increase in daily infections in parts of Asia, the United States, and Australia.

As of 20 July 2021, the dangerous virus variant had spread to 124 countries, and the WHO indicated that it was certainly becoming the dominant strain globally.