‘American Covid’ strain cases rise in UK, hospital admissions surge by 50%. Cases of XFG variant of SARS-CoV-2, also known as the “American Covid” strain, are rising in the UK, with increases in positive tests and hospital admissions reported. The rate of positive Covid-19 tests in UK hospitals rose from 5.9% to 7.0%, while hospital admission rates surged by nearly 50%. Hospital admissions were highest in London, where they increased by 79%.