Scientists more widely took note of this variant in early December 2020, when a phylogenetic tree showing viral sequences from Kent, United Kingdom looked unusual.

[7][8] On 2 February 2021, Public Health England reported that they had detected "[a] limited number of B.1.1.7 VOC-202012/01 genomes with E484K mutations",[9] which they dubbed Variant of Concern 202102/02 (VOC-202102/02).

Imperial College London investigated over a million people in England while the Alpha variant was dominant and discovered a wide range of further symptoms linked to Covid.

They are believed to be useful in stopping the chain of transmission of the virus by providing the means to rapidly identify large numbers of cases as part of a mass-testing program.

[26] As of the end of 2020, German, British, and American health authorities and experts believe that existing vaccines will be as effective against VOC-202012/01 as against previous variants.

[31] A week later a Research and analysis report from PHE gave a total of 77 confirmed and probable cases involving the E484K mutation across the UK, in two variants, VUI-202102/01 and VOC-202102/02, the latter described as 'B.1.1.7 with E484K'.

[40] The Danish Statens Serum Institut in comparison calculated it to be 55% (48%–62%) more transmissible in Denmark based upon the observed development of its relative frequency from 4 January to 12 February 2021.

[42] On 18 December 2020—early on in the risk assessment of the variant—the UK scientific advisory body New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG) concluded that they had moderate confidence that VOC-202012/01 was substantially more transmissible than other variants, but that there were insufficient data to reach any conclusion on underlying mechanism of increased transmissibility (e.g. increased viral load, tissue distribution of virus replication, serial interval etc.

[46] Similarly, in Ireland, the variant—as indicated by the missing S gene[c] detection (S-gene target failure [SGTF]), which historically was rare—went from 16.3% to 46.3% of cases in two weeks.

[22] Chand et al. concluded that "[i]t is highly likely that N501Y affects the receptor-binding affinity of the spike protein, and it is possible that this mutation alone or in combination with the deletion at 69/70 in the N-terminal domain (NTD) is enhancing the transmissibility of the virus".

At prime minister Boris Johnson's briefing the following day, officials said that there was "no evidence" as of that date that the variant caused higher mortality or was affected differently by vaccines and treatments;[64] Vivek Murthy agreed with this.

[68] A UK case-control study for 54,906 participants, testing positive for SARS-CoV-2 between 1 October 2020 and 29 January 2021 in the community setting (not including vulnerable persons from care centres and other public institutions), reported that patients infected with the Alpha variant (VOC 202012/1) had a hazard ratio for death within 28 days of testing of 1.64 (95% confidence interval 1.32-2.04), as compared with matched patients positive for other variants of SARS-CoV-2.

[71] The study also noted that "SARS-CoV-2 ORF8 is an immunoglobulin (Ig)–like protein that modulates pathogenesis", that "SARS-CoV-2 ORF8 mediates major histocompatibility complex I (MHC-I) degradation", and that "SARS-CoV-2 ORF8 suppresses type I interferon (IFN)–mediated antiviral response".

[56] The HV 69–70 deletion has, however, been discovered "in viruses that eluded the immune response in some immunocompromised patients",[72] and has also been found "in association with other RBD changes".

[83][75] As of 23 March, the Alpha variant had been detected in 125 out of 241 sovereign states and dependencies (or 104 out of 194 WHO member countries),[e] of which some had reported existence of community transmission while others so far only found travel related cases.

[101] Leumit Health Care Services however analysed with the proxy test RT-PCR (SGTF) and found the variant at a rate of 3‑4% on 15 December.

[126] In Germany, the largest and probably most representative national survey published by the Robert Koch Institute (entitled RKI-Testzahlerfassung), determined the share of circulating COVID-19 variants for the latest week by analysing 53,272 COVID-19 positive samples either by genome sequencing or RT-PCR proxy tests, with data collected on a voluntary basis from 84 laboratories from the university / research / clinical / outpatient sector - spread evenly across the nation.

[131] In Sweden, the national authorities initially expected the variant would become dominant around week 12–14 under the assumption of 50% increased transmissibility compared to the original virus.

[206] On 6 January 2021, the US Centers for Disease Control and Prevention announced that it had found at least 52 confirmed cases in California, Florida, Colorado, Georgia, and New York.

[207] In the following days, more cases of the variant were reported in other states, leading former CDC director Tom Frieden to express his concerns that the U.S. will soon face "close to a worst-case scenario".

[224] On 8 January, Romania reported its first case of the variant, an adult woman from Giurgiu County who declared not having left the country recently.

[241] In early January, an outbreak linked to a primary school led to the detection of at least 30 cases of the new variant in the Bergschenhoek area of the Netherlands, signifying local transmission.

[251] The N501Y mutation arose independently multiple times in different locations: The Alpha variant (lineage B.1.1.7) was first detected in early December 2020 by analysing genome data with knowledge that the rates of infection in Kent were not falling despite national restrictions.

[261] Backwards tracing using genetic evidence suggests lineage B.1.1.7 emerged in September 2020 and then circulated at very low levels in the population until mid-November.

The increase in cases linked to the variant first became apparent in late November when Public Health England (PHE) was investigating why infection rates in Kent were not falling despite national restrictions.

[263] It has been suggested that the variant may have originated in a chronically infected immunocompromised person, giving the virus a long time to replicate and evolve.

[264][5][265][266] In the presence of a more transmissible variant, stronger physical distancing and lockdown measures were opted for to avoid overwhelming the population due to its tendency to grow exponentially.

[267] All countries of the United Kingdom were affected by domestic travel restrictions in reaction to the increased spread of the virus—at least partly attributed to Alpha—effective from 20 December 2020.

[278] The usefulness of travel bans has been contested as limited in cases where the variant has likely already arrived, especially if the estimated growth rate per week of the virus is higher locally.

[281] In March 2022, the World Health Organization listed the Alpha, Beta and Gamma variants as previously circulating citing lack of any detected cases in the prior weeks and months.