On 26 November 2021, the South African National Institute for Communicable Diseases announced that 30,904 COVID-tests (in one day) detected 2,828 new COVID infections (a 9.2% positivity rate). One week later, on 3 December 2021, the NICD announced that 65,990 COVID tests had found 16,055 new infections (5.7 times as many as seven days before; positive rate 24.3%) and that 72 percent of them were found in Gauteng. This province of South Africa is densely populated at about 850 inhabitants per km2. Gauteng's capital Johannesburg is a megacity (about 5.5 million inhabitants in the city itself plus 9.5 million in the urban region). In November 2021, the transmissibility of the<unk><unk> , as compared to the Delta<unk>  or other<unk> s of the COVID-19 virus, was still uncertain.<unk>  is frequently able to infect previously Covid-positive people. It has been estimated the<unk><unk>  diverged in late September or early October 2021, based on<unk>  genome comparisons. Sequencing data suggests that<unk>  had become the dominant<unk>  in South Africa by November 2021, the same month where it had been first identified in the country. Phylogeny suggests a recent emergence. Data from South Africa suggests that<unk>  has a pronounced growth advantage there. However, this may be due to transmissibility or immune escape related, or both." Also the serial interval plays a role in the growth. Detectable changes in levels of COVID-19 in wastewater samples from South Africa's Gauteng province were seen as early as 17–23 October (week 42). The National Institute for Communicable Diseases reports that children under the age of 2 make up 10% of total hospital admissions in the<unk>  point of discovery Tshwane in South Africa. Data on the S gene target failure (SGTF) of sampled cases in South Africa indicates a growth of 21% per day relative to Delta, generating an increased reproduction number by a factor of 2.4.<unk>  became the majority strain in South Africa around 10 November. Another analysis showed 32% growth per day in Gauteng, South Africa, having become dominant there around 6 November. In the UK, the logarithmic growth rate of<unk> -associated S gene target failure (SGTF) cases over S gene target positive (SGTP) cases was estimated at 0.37 per day, which is exceptionally high. Furthermore, by 14 December it appears to have become the most dominant strain. Without presuming behavior change in response to the<unk> , a million infections per day by December 24 are projected for a 2.5 days doubling time. In Denmark, the growth rate has been roughly similar with a doubling time of about 2–3 days, it having become the most prevalent strain on 17 December. Switzerland is not far behind. In Germany<unk>  became the most prevalent<unk>  on January 1. In Scotland,<unk>  apparently became the most prevalent<unk>  on 17 December. In the Canadian province of Ontario it became the most prevalent strain on 13 December. In the US, the<unk>  appears to have become the most prevalent strain on December 18, growing at 0.24 per day. In Portugal,<unk>  had reached 61.5% of cases on 22 December. In Belgium, the strain has become the most prevalent on 25 December, and in the Netherlands on 28 December. In Italy, it had reached 28% of cases on 20 December and was doubling every two days, while it became the dominant<unk>  in Norway on 25 December. In France, it made up about 15% of COVID-19 cases in mid-December, but around 27 December it had increased to more than 60%. Researchers recommend sampling at least 5% of COVID-19 patient samples in order to detect<unk>  or other emerging<unk> s. During January 2022, in Denmark the BA.2<unk>  grew at ~0.10 per day (+11% per day) as a ratio to BA.1 (the legacy<unk><unk> , and became the dominant strain in week 2, 2022. In the United Kingdom, the BA.2<unk>  was growing at ~0.11 per day (+12% per day) as a ratio to BA.1. On 13 January 2022, the BBC reported that the hospitalization rate was higher in the US and Canada than in Europe and South Africa. This was attributed to a combination of a greater number of elderly people than in South Africa, greater prevalence of comorbidities such as hypertension and obesity than in Europe, higher indoor transmission due to the winter, lower vaccination rate in the US than in Europe and Canada, and a possible still high prevalence of the Delta<unk> , which more often leads to hospitalization.
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