|Part of a series on the|
The Delta variant [ when? ]is a variant of SARS-CoV-2, the virus that causes COVID-19. It was first detected in India in late 2020. The Delta variant was named on 31 May 2021 and had spread to over 163 countries by 24 August 2021. The World Health Organization (WHO) indicated that the Delta variant is becoming the dominant strain globally.
It has mutations in the gene encoding the SARS-CoV-2 spike proteincausing 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. It is thought to be one of the most transmissible respiratory viruses known. 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% vis-à-vis 10.2% for the Alpha variant; the case fatality rate for those 386,835 people with Delta is 0.3%, where 46% of the cases and 6% of the deaths are unvaccinated and below 50 years old. Immunity from previous recovery or COVID-19 vaccines are effective in preventing severe disease or hospitalisation from infection with the 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 using May data 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 deadly 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, Australia, and New Zealand.
The Delta variant has mutations in the gene encoding the SARS-CoV-2 spike proteincausing the substitutions D614G, T478K, P681R and L452R. It is identified as the 21A clade under the Nextstrain phylogenetic classification system.
The virus has also been referred to by the term "Indian Variant"as it was originally detected in India. However, the Delta variant is only one of three variants of the lineage B.1.617, all of which were first detected in India. At the end of May 2021, the WHO assigned the label Delta to lineage B.1.617.2 after introducing a new policy of using Greek letters for variants of concern and variants of interest.
There are three sublineages of lineage B.1.617 categorised so far.
B.1.617.1 (Kappa variant) was designated a Variant Under Investigation in April 2021 by Public Health England. Later in April 2021, two other variants B.1.617.2 and B.1.617.3 were designated as Variants Under Investigation. While B.1.617.3 shares the L452R and E484Q mutations found in B.1.617.1, B.1.617.2 lacks the E484Q mutation. B.1.617.2 has the T478K mutation, not found in B.1.617.1 and B.1.617.3.Simultaneously, the ECDC released a brief maintaining all three sublineages of B.1.617 as VOI, estimating that a "greater understanding of the risks related to these B.1.617 lineages is needed before any modification of current measures can be considered".
|Sources: CDC Covariants.org|
The Delta/ B.1.617.2 genome has 13 mutations (15 or 17 according to some sources,[ which? ] depending on whether more common mutations are included) which produce alterations in the amino-acid sequences of the proteins it encodes. Four of them, all of which are in the virus's spike protein code, are of particular concern:
The E484Q mutation is not present in the B.1.617.2 genome.
As of August 2021, Delta have been subdivided in the Pango lineage designation system into variants from AY.1 to AY.38. However, there are no information on whether such classification correlate with biological characteristic changes of the virus.It is said that, as of August 2021, AY.4 to AY.11 are predominant in the UK, AY.12 in Israel, AY.2, AY.3, AY.13, AY.14, AY.25 in the US, AY.20 in the US and Mexico, AY.15 in Canada, AY.16 in Kenya, AY.17 in Ireland and Northern Ireland, AY.19 in South Africa, AY.21 in Italy and Switzerland, AY.22 in Portugal, AY.24 in Indonesia, and AY.23 in Indonesia, Singapore, Japan, and South Korea.
As of 30 August 2021, the AY.4 variant accounted for approximately 59% of cases in the United States.
Delta with K417N corresponds to lineages AY.1 and AY.2and has been nicknamed "Delta plus" or "Nepal variant". It has the K417N mutation, which is also present in the Beta variant. The exchange at position 417 is a lysine-to-asparagine substitution.
As of mid-October 2021, the AY.3 variant accounted for a cumulative prevalence of approximately 5% in the United States, and 2% worldwide.In mid-October the AY.4.2 Delta sublineage was expanding in England, and being monitored and assessed. It contains mutations A222V and Y145H in its spike protein, not considered of particular concern. It has been suggested that AY.4.2 might be 10-15% more transmissible than the original Delta variant, but this would not lead to a large increase in cases.
The most common symptoms may have changed from the most common symptoms previously associated with standard COVID-19. Infected people may mistake the symptoms for a bad cold and not realize they need to isolate. Common symptoms reported have been headaches, sore throat, a runny nose or a fever. [ medical citation needed ] In the United Kingdom, where the Delta variant makes up 91 percent of new cases, one study found that the most reported symptoms were headache, sore throat, and runny nose.
|Disease or infection||Severe: protection retained|
Symptomatic: possibly reduced protection
|Severe disease||: AstraZeneca-Vaxzevria(1), Moderna(1), Pfizer-BioNTech(2)|
|Symptomatic disease|| to : Pfizer-BioNTech(3) |
|Infection||: AstraZeneca-Vaxzevria(1), Pfizer-BioNTech(1)|
Symbols indicate the magnitude of vaccine effectiveness (VE) reduction. Note that VE reduction doesn't mean loss of protection, because original high protection rate (such as 95%) with some reduction (such as 10%) would still retain protection (such as 85%). Enclosed in parentheses is the number of studies supporting the indication. Studies vary in population, outcome definitions, study design, etc., which may explain differences in VE estimates for a product in different studies. Also, the reductions represent VE estimates and do not represent uncertainties around the estimates which may vary substantially across studies. The VE reductions should be interpreted with these limitations.
: VE reduces <10%, or VE >90% without comparator
|Effects on Neutralization (fully vaccinated)|
| to : Anhui-ZIFIVAX(2), Covaxin(3) |
: Janssen(3), Moderna(3), Covishield(2)
to : AstraZeneca-Vaxzevria(4), Pfizer-BioNTech(8)
:Moderna & Pfizer-BioNTech(1)*
to : Coronavac(2)
|Symbols indicate the magnitude of neutralization reduction with full vaccination. Enclosed in parentheses is the number of studies supporting the indication.|
: Neutralization reduces <2-fold
WHO has not issued preventative measures against Delta specifically; non-pharmaceutical measures recommended to prevent wild type COVID-19 should still be effective. These would include washing hands, wearing a mask, maintaining distance from others, avoiding touching the mouth, nose or eyes, avoiding crowded indoor spaces with poor ventilation especially where people are talking, going to get tested if one develops symptoms and isolating if one becomes sick.Public Health authorities should continue to find infected individuals using testing, trace their contacts, and isolate those who have tested positive or been exposed. Event organizers should assess the potential risks of any mass gathering and develop a plan to mitigate these risks. See also Non-pharmaceutical intervention (epidemiology).
ICMR found that convalescent sera of the COVID-19 cases and recipients of Bharat Biotech's BBV152 (Covaxin) were able to neutralise VUI B.1.617 although with a lower efficacy.
Anurag Agrawal, the director of the Institute of Genomics and Integrative Biology (IGIB), said the study on the effectiveness of the available vaccines on lineage B.1.617 suggests that post-vaccination, the infections are milder.
Anthony Fauci, the Chief Medical Advisor to the President of the United States, has also expressed his confidence regarding the preliminary results. In an interview on 28 April, he said:
This is something where we're still gaining data daily. But the most recent data was looking at convalescent sera of COVID-19 cases and people who received the vaccine used in India, the Covaxin. It was found to neutralise the 617 variants.
Another study by the Centre for Cellular and Molecular Biology (CCMB) in Hyderabad found Covishield (Oxford–AstraZeneca) vaccinated sera offers protection against lineage B.1.617.
A study conducted by the Public Health England, has found that compared to those who were unvaccinated those who were vaccinated with either the Pfizer-BioNTech or AstraZeneca-Oxford had 33% less instances of symptomatic disease caused by the variant after the first dose. Among those who were two weeks after the receiving their second dose of the Pfizer-BioNTech vaccine 88% less subjects had symptomatic disease from the Delta variant versus those that were unvaccinated. Among those who were two weeks after the receiving their second dose of the AstraZeneca-Oxford vaccine 60% less subjects had symptomatic disease from the Delta variant versus those that were unvaccinated.
A study by a group of researchers from the Francis Crick Institute, published in The Lancet , shows that humans fully vaccinated with the Pfizer-BioNTech vaccine are likely to have more than five times lower levels of neutralizing antibodies against the Delta variant compared to the original COVID-19 strain.
In June 2021, Public Health England announced it had conducted a study which found that after two shots, the Pfizer-BioNTech vaccine and the AstraZeneca vaccine are respectively 96% and 92% effective at preventing hospitalisation from the Delta variant.
On July 3, researchers from the universities of Toronto and Ottawa in Ontario, Canada, released a preprint study suggesting that the Moderna vaccine may be effective against death or hospitalization from the Delta variant. [ unreliable medical source? ]
In a study of the University of Sri Jayewardenepura in July 2021 found the Sinopharm BBIBP-CorV vaccine caused seroconversion in 95% of individuals studied that had received both doses of the vaccine. The rate was higher in 20-39 age group (98.9%) but slightly lower in the over 60 age group (93.3%). Neutralising antibodies were present among 81.25% of the vaccinated individuals studied.
On 29 June 2021, the director of the Gamaleya Institute, Denis Logunov, said that Sputnik V is about 90% effective against the Delta variant.
On July 21, researchers from Public Health England published a study finding that the Pfizer vaccine was 93.7% effective against symptomatic disease from Delta after 2 doses, while the Astrazeneca vaccine was 67% effective.
On August 2, several experts expressed concern that achieving herd immunity may not currently be possible because the Delta variant is transmitted among those immunized with current vaccines.
On August 10, a study showed that the full vaccination coverage rate is correlated inversely to the SARS-CoV-2 delta variant mutation frequency in 16 countries (R-squared=0.878). Data strongly indicates that full vaccination against COVID-19 may slow down virus evolution.
In vitro experiments suggest that bamlanivimab may not be effective against Delta on its own.At high enough concentrations, casirivimab, etesevimab and imdevimab appear to still be effective. A preprint study suggests that sotrovimab may also be effective against Delta. Doctors in Singapore have been using supplemental oxygen, remdesivir and corticosteroids on more Delta patients than they did on previous variants.
|Transmissibility||Increased transmissibility and secondary attack rate, similar transmissibility between vaccinated and unvaccinated individuals.|
|Virulence||Increased risk of hospitalization|
|Reinfection||Decreased neutralizing activity|
|Diagnostics||No impacts yet reported|
|*Generalized finding compared to other strains, based on evidence including non-peer-reviewed publications.|
UK scientists have said that the Delta variant is between 40% and 60% more transmissible than the previously-dominant Alpha variant, which was first identified in the UK (as the Kent variant). – basic reproduction number, or the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection –for the first detected SARS-CoV-2 virus is 2.4-2.6, whereas Alpha's reproduction number is 4-5 and Delta's is 5–9. These basic reproduction numbers can be compared to MERS (0.29-0.80 ), seasonal influenza (1.2-1.4 ), Ebola (1.4-1.8 ), common cold (2-3 ), SARS (2–4 ), smallpox (3.5-6 ), and chickenpox (10-12 ). Due to Delta's high transmissibility even those that are vaccinated are vulnerable, albeit to a lesser extent.Given that Alpha is already 150% as transmissible as the original SARS-CoV-2 strain that emerged in late 2019 in Wuhan, and if Delta is 150% as transmissible as Alpha, then Delta may be 225% as transmissible as the original strain. BBC reported that
A studypublished online (not peer-reviewed) by Guangdong Provincial Center for Disease Control and Prevention may partly explain the increased transmissibility: people with Delta infection had 1,000 times more copies of the virus in the respiratory tracts than those with Wuhan strain infection; and it took on average 4 days for people infected with Delta for the virus to be detectable compared to 6 days with the Wuhan strain.
Surveillance data from the U.S., Germany and the Netherlands indicates the Delta variant is growing by about a factor of 4 every two weeks with respect to the Alpha variant.
In India, the United Kingdom,Portugal, Russia, Mexico, Australia, Indonesia, South Africa, Germany, Luxembourg, the United States, the Netherlands, Denmark, France and probably many other countries, the Delta variant had become the dominant strain by July 2021. There is typically a three-week lag between cases and variant reporting. As of July 20, this variant had spread to 124 countries, and WHO had indicated that it was becoming the dominant strain, if not one already.
In the Netherlands, the virus was still able to propagate significantly in the population with over 93.4% of blood donors being tested positive for Sars-Cov-2 antibodies after week 28, 2021. Many people there are not fully vaccinated, so those antibodies would have been developed from exposure to the wild virus or from a vaccine.
A preprint found that the viral load in the first positive test of infections with the variant was on average ∼1000 times higher than with compared infections during 2020.Preliminary data from a study with 100,000 volunteers in the UK from May to July 2021, when Delta was spreading rapidly, indicates that vaccinated people who test positive for COVID-19, including asymptomatic cases, have a lower viral load in average. Data from the US, UK, and Singapore indicate that vaccinated people infected by Delta may have viral loads as high as unvaccinated infected people, but might remain infectious for a shorter period.
Surveillance data from the Indian government's Integrated Disease Surveillance Programme (IDSP) shows that around 32% of patients, both hospitalised and outside hospitals, were aged below 30 in the second wave compared to 31% during the first wave, among people aged 30–40 the infection rate stayed at 21%. Hospitalisation in the 20-39 bracket increased to 25.5% from 23.7% while the 0-19 range increased to 5.8% from 4.2%. The data also showed a higher proportion of asymptomatic patients were admitted during the second wave, with more complaints of breathlessness.
A few early studies suggest the Delta variant causes more severe illness than other strains.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 June 11, Public Health England released a report finding that there was "significantly increased risk of hospitalization" from Delta as compared with Alpha; the risk was approximately twice as high for those infected with the Delta variant. On June 14, researchers from Public Health Scotland found that the risk of hospitalization from Delta was roughly double that of from Alpha. On July 7, a preprint study from epidemiologists at the University of Toronto found that Delta had a 120% greater – or more than twice as large – risk of hospitalization, 287% greater risk of ICU admission and 137% greater risk of death compared to non-variant of concern strains of SARS-COV-2. However, on July 9, Public Health England reported that the Delta variant in England had a case fatality rate (CFR) of 0.2%, while the Alpha variant's case fatality rate was 1.9%, although the report warns that "case fatality rates are not comparable across variants as they have peaked at different points in the pandemic, and so vary in background hospital pressure, vaccination availability and rates and case profiles, treatment options, and impact of reporting delay, among other factors." James McCreadie, a spokesperson for Public Health England, clarified "It is too early to assess the case fatality ratio compared to other variants."
A Canadian study released on 5 October, 2021 revealed that the Delta variant caused a 108 percent rise in hospitalization, 235 percent increase in ICU admission, and a 133 percent surge in death compared to other variants. is more serious and resulted in an increased risk of death compared to previous variants, odds that are significantly decreased with immunization.
By 22 June 2021[ needs update ], more than 4,500 sequences of the variant had been detected in about 78 countries. Reported numbers of sequences in countries with detections are:
|Cases by country|
|Country/Area||Confirmed Delta variant cases:|
(PANGOLIN) as of 2 September
(GISAID) as of 15 September
|Cases (other sources)|
as of 29 September 2021
|United Kingdom||239,594||418,611||669,401||22 February 2021|
|United States||86,350||302,001||99.4% of cases||23 February 2021|
|Fiji||-||-||47,639||19 April 2021|
|India||15,693||24,877||5 October 2020|
|Denmark||23,365||44,372||8 March 2021|
|Canada||1,411||14,476||80,560||15 March 2021|
|Japan||1,374||12,840||1,583 L452R: 7,143||28 March 2021|
|Germany||9,252||36,505||1 March 2021|
|Italy||8,027||15,031||2 April 2021|
|Spain||6,443||15,332||22 April 2021|
|France||10,063||28,077||21 February 2021|
|Belgium||4,942||12,265||25 March 2021|
|Portugal||4,151||6,908||5 April 2021|
|Sweden||5,587||19,887||26 March 2021|
|The Netherlands||7,886||16,028||6 April 2021|
|South Africa||2,582||6,175||4||30 April 2021|
|Mexico||3,110||7,537||5 April 2021|
|Ireland||4,461||10,559||26 February 2021|
|Singapore||2,727||4,573||26 February 2021|
|Russia||1,468||2,469||16||21 April 2021|
|Indonesia||1,623||2,613||3 April 2021|
|Switzerland||5,150||13,105||29 March 2021|
|Israel||2,460||3,375||41||16 April 2021|
|Australia||3,504||9,118||9,325||16 March 2021|
|Turkey||5,489||40,511||5||28 April 2021|
|Austria||1,578||3,622||17 April 2021|
|Norway||1,241||4,273||1||15 April 2021|
|Botswana||196||468||2||28 April 2021|
|Bangladesh||283||702||9||28 April 2021|
|Qatar||121||179||19 April 2021|
|DR Congo||19||228||5||3 May 2021|
|Finland||1,570||4,217||2,876||18 March 2021|
|Poland||491||1,690||16||26 April 2021|
|Thailand||236||420||2||24 April 2021|
|Nepal||100||138||9||28 April 2021|
|Luxembourg||1,153||1,227||15 April 2021|
|China||86||307||24 April 2021|
|Bahrain||117||618||5 April 2021|
|New Zealand||92||1,008||107||9 March 2021|
|Angola||6||28||14 January 2021|
|Hong Kong||153||10||22 April 2021|
|South Korea||706||2,426||26 March 2021|
|Jordan||5||19||21 April 2021|
|Czech Republic||787||1,859||24 April 2021|
|Greece||17||800||23 March 2021|
|Guadeloupe||-||149||10 March 2021|
|Argentina||4||77||2||24 April 2021|
|Morocco||3||3||2||3 May 2021|
|Sint Maarten||-||896||19 March 2021|
|Algeria||17||18||6||28 July 2021|
|Aruba||90||1,285||16 April 2021|
|Cambodia||171||243||5 April 2021|
|Curacao||-||234||23 April 2021|
|Cyprus||-||1||4||19 May 2021|
|Haiti||-||1||(number unreported)||27 July 2021|
|Iran||11||11||3||11 May 2021|
|Kenya||256||694||5||17 July 2021|
|Kyrgyzstan||-||-||(number unreported)||16 May 2021|
|Malaysia||146||763||10 April 2021|
|Nigeria||36||250||1||7 August 2021|
|Romania||294||504||26 April 2021|
|Reunion||54||112||4 May 2021|
|Slovenia||-||2,973||20 April 2021|
|Sri Lanka||117||467||1||30 April 2021|
|Uganda||134||163||1||26 March 2021|
|Philippines||11||12||3,366||11 May 2021|
|Uzbekistan||30||47||(number unreported)||25 June 2021|
|Vietnam||54||188||12||18 April 2021|
|Brazil||437||2,688||1051||20 May 2021|
|Guam||-||14||26 April 2021|
|Ghana||101||267||20 April 2021|
|Pakistan||49||199||16 May 2021|
|Lithuania||899||3,911||1||17 June 2021|
|Croatia||479||1,434||11 June 2021|
|Monaco||34||48||15 May 2021|
|Malawi||5||114||30 April 2021|
|Slovakia||353||1,360||15 June 2021|
|Myanmar||12||18||1 June 2021|
|Barbados||3||23||24 May 2021|
|Kuwait||108||161||5 June 2021|
|Georgia||19||39||15 May 2021|
|Malta||42||63||23 June 2021|
|Senegal||13||33||6 May 2021|
|Peru||6||104||10 June 2021|
|Mauritius||15||17||8 May 2021|
|Chile||64||231||13 June 2021|
|Taiwan||3||5||14 June 2021|
|Bulgaria||231||783||5 April 2021|
|Anguilla||-||7||20 April 2021|
|Albania||11||11||13 July 2021|
|Azerbaijan||-||1||14 July 2021|
|Bosnia and Herzegovina||31||31||26 July 2021|
|Bonaire||-||116||13 July 2021|
|Burundi||3||3||31 May 2021|
|Colombia||-||21||3 July 2021|
|Costa Rica||35||174||7 July 2021|
|Crimea||-||21||1 July 2021|
|Ecuador||89||115||20 July 2021|
|Gambia||42||82||12 July 2021|
|French Guiana||53||132||22 July 2021|
|Kosovo||-||30||2 May 2021|
|Latvia||22||22||27 May 2021|
|Lebanon||-||80||3 July 2021|
|Maldives||6||168||31 July 2021|
|Moldova||11||11||6 July 2021|
|North Macedonia||6||38||11 July 2021|
|Oman||8||113||17 May 2021|
|Paraguay||4||8||8 July 2021|
|Serbia||5||5||6 July 2021|
|Södermanland||-||1||7 July 2021|
|South Sudan||-||29||7 June 2021|
|Tunisia||-||1||21 May 2021|
|United Arab Emirates||-||28||23 June 2021|
|Ukraine||13||34||24 June 2021|
|Västra Götaland||-||86||19 July 2021|
|Zambia||82||82||29 May 2021|
|East Timor||-||-||12||8 August 2021|
|Venezuela||-||1||7 July 2021|
|Northern Mariana Islands||2||19||7 July 2021|
|Republic of Congo||-||1||15 July 2021|
|Dominican Republic||-||1||3 May 2021|
|Iraq||2||2||27 April 2021|
|Rwanda||91||98||9 July 2021|
|Liechtenstein||-||20||15 July 2021|
|Estonia||-||460||21 July 2021|
|Guatemala||4||86||29 July 2021|
|Andorra||-||12||17 July 2021|
|Suriname||-||17||3 August 2021|
|Hungary||-||-||14||22 July 2021|
|Martinique||8||69||10 August 2021|
|Iceland||-||3,767||30 August 2021|
|Gibraltar||-||848||5 September 2021|
|Mozambique||-||66||16 July 2021|
|Montenegro||-||93||8 August 2021|
|Jamaica||-||10||23 July 2021|
|Ethiopia||-||8||16 August 2021|
|Papua New Guinea||-||8||10 August 2021|
|Honduras||-||2||31 July 2021|
|Egypt||-||1||15 July 2021|
|Montserrat||-||1||1 August 2021|
|Liberia||-||44||10 July 2021|
|Antigua and Barbuda||-||34||6 August 2021|
|Armenia||-||50||5 August 2021|
|Brunei||-||28||17 August 2021|
|British Virgin Islands||-||1||27 July 2021|
|Cayman Islands||-||11||30 July 2021|
|Central African Republic||-||17|
|Gabon||-||7||2 August 2021|
|Grenada||-||3||26 July 2021|
|Saint Lucia||-||4||26 July 2021|
|Saint Vincent and the Grenadines||-||2||8 August 2021|
|Togo||-||130||31 July 2021|
|Trinidad and Tobago||-||2||3 August 2021|
|Turks and Caicos Islands||-||4||12 July 2021|
|Zimbabwe||-||96||26 July 2021|
|Burkina Faso||-||21||21 April 2021|
|Afghanistan||-||20||24 May 2021|
|Belize||-||22||30 June 2021|
|Saint Barthelemy||-||3||17 August 2021|
|Mali||-||2||11 August 2021|
|Benin||-||47||23 July 2021|
|Equatorial Guinea||-||14||30 August 2021|
|U.S. Virgin Islands||-||184||18 August 2021|
|Puerto Rico||-||1,081||9 September 2021|
|Sierra Leone||-||8||8 September 2021|
|World (167 countries)||Total: 471,067|
The first cases of the variant outside India were detected in late February 2021, including the United Kingdom on 22 February, the United States on 23 February and Singapore on 26 February.
British scientists at Public Health England redesignated the B.1.617.2 variant on 7 May 2021 as "variant of concern" (VOC-21APR-02),after they flagged evidence in May 2021 that it spreads more quickly than the original version of the virus. Another reason was that they identified 48 clusters of B.1.617.2, some of which revealed a degree of community transmission. With cases from the Delta variant having risen quickly, British scientists considered the Delta variant having overtaken the Alpha variant as the dominant variant of SARS-CoV-2 in the UK in early June 2021. Researchers at Public Health England later found that over 90% of new cases in the UK in the early part of June 2021 were the Delta variant; they also cited evidence that the Delta variant was associated with an approximately 60% increased risk of household transmission compared to the Alpha variant.
Canada's first confirmed case of the variant was identified in Quebec on 21 April 2021, and later the same day 39 cases of the variant were identified in British Columbia.Alberta reported a single case of the variant on 22 April 2021. Nova Scotia reported two Delta variant cases in June 2021.
Fiji also confirmed its first case of the variant on 19 April 2021 in Lautoka, and has since then climbed up to 47,000 cases and counting.The variant has been identified as a super-spreader and has led to the lockdowns of five cities (Lautoka, Nadi, Suva, Lami and Nausori), an area which accounts for almost two-thirds of the country's population.
On 29 April 2021, health officials from Finland's Ministry of Social Affairs and Health (STM) and the Finnish Institute for Health and Welfare (THL) reported that the variant had been detected in three samples dating back to March 2021.
The Philippines confirmed its first two cases of the variant on 11 May 2021, despite the imposed travel ban of the country from the nations in the Indian subcontinent (except for Bhutan and Maldives). Both patients have no travel history from India for the past 14 days, but instead from Oman and UAE.
North Macedonia confirmed its first case of the variant on 7 June 2021 after a person who was recovering from the virus in Iraq was transported to North Macedonia. In a laboratory test, the variant was detected in the person. On 22 June 2021, the country reported its second case of the Delta variant in a colleague of the first case who had also been in Iraq and who subsequently developed symptoms.
The detection of B.1.617 was hampered in some countries by a lack of specialised kits for the variant and laboratories that can perform the genetic test.For example, as of 18 May, Pakistan had not reported any cases, but authorities noted that 15% of COVID-19 samples in the country were of an "unknown variant"; they could not say if it was B.1.617 because they were unable to test for it. Other countries had reported travellers arriving from Pakistan that were infected with B.1.617.
In June 2021, scientist Vinod Scaria of India's Institute of Genomics and Integrative Biology highlighted the existence of the B.1.617.2.1 variant, also known as AY.1 or Delta plus, which has an additional K417N mutation compared to the Delta variant.B.1.617.2.1 was detected in Europe in March 2021, and has since been detected in Asia and America.
On 9 July 2021, Public Health England issued Technical Briefing 18 on SARS-CoV-2 variants, documenting 112 deaths among 45,136 UK cases of SARS-CoV-2 Delta variant with 28 days follow-up with a fatality rate of 0.2%.Briefing 16 notes that "[M]ortality is a lagged indicator, which means that the number of cases who have completed 28 days of follow up is very low – therefore, it is too early to provide a formal assessment of the case fatality of Delta, stratified by age, compared to other variants." Briefing 18 warns that "Case fatality is not comparable across variants as they have peaked at different points in the pandemic, and so vary in background hospital pressure, vaccination availability and rates and case profiles, treatment options, and impact of reporting delay, among other factors." The most concerning issue is the logistic growth rate of 0.93/week relative to Alpha. This means that per week, the number of Delta samples/cases is growing by a 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.
After the rise in cases from the second wave, at least 20 countries imposed travel bans and restrictions on passengers from India in April and May. UK prime minister Boris Johnson cancelled his visit to India twice, while Japanese Prime Minister Yoshihide Suga postponed his April trip.
In May 2021, residents of two tower blocks in Velbert, Germany, were quarantined after a woman in the building tested positive for the Delta variant.
In May, Delhi Chief Minister Arvind Kejriwal said that a new coronavirus variant from Singapore was extremely dangerous for children and could result in a third wave in India.
From 16 May to 13 June 2021, as well as 22 July 2021 to 10 August 2021; Singapore entered lockdowns, known as "Phase 2 Heightened Alert", similar to 2020.
On 14 June, the British prime minister Boris Johnson announced that the proposed end of all restrictions on 21 June in the United Kingdom was delayed for up to four weeks and vaccination roll-out was accelerated following concerns over the Delta variant, which accounted for the vast majority (90%) of new infections.UK scientists have said that the Delta variant is between 40% and 60% more transmissible than the previously-dominant Alpha variant, which was first identified in the UK (as the Kent variant).
On 23 June, the province of Ontario in Canada accelerated 2nd dose vaccine appointments for people living in Delta hot spots such as Toronto, Peel and Hamilton.
On 25 June, Israel restored their mask mandate citing the threat of Delta.
On 28 June, Sydney and Darwin in Australia went back into lockdown because of Delta outbreaks.South Africa banned indoor and outdoor gatherings apart from funerals, imposed a curfew, and banned the sale of alcohol.
On 3 July, the islands of Bali and Java in Indonesia went into emergency lockdown.
On 8 July, Japanese Prime Minister Yoshihide Suga announced that Tokyo would once again enter a state of emergency, and that most spectators would be barred from attending the Olympics set to start there on 23 July.
On 9 July, Seoul, South Korea ramped up restrictions urging people to wear masks outdoors, and limiting the size of gatherings.
On 12 July, French President Emmanuel Macron announced that all health care workers will need to be vaccinated by 15 September and that France will start using health passports to enter bars, cafés, restaurants and shopping centres from August.
Los Angeles announced it will require masks indoors starting 17 July 2021.
The United Kingdom lifted most COVID-19 restrictions on 19 July, despite a surge in cases as the Delta variant became dominant. The government cited the protection and wide coverage of the COVID-19 vaccination programme, although health experts expressed concern at the move.
On 23 July, Vietnam extended its lockdown of Ho Chi Minh City to 1 August, and announced lockdown restrictions would be put in place in Hanoi, affecting a third of the country's population. The Delta variant had brought upon the country's largest outbreak to date, after mostly successful containment measures throughout 2020.
On 17 August, New Zealand went into an alert level 4 lockdown, following a positive case being reported in Auckland. More cases soon followed in the Coromandel Peninsula.This was the first reported community transmission case in the country in 170 days (since February 2021).
The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identified in the Chinese city of Wuhan in December 2019; a lockdown in Wuhan and other cities in surrounding Hubei failed to contain the outbreak, and it quickly spread to other parts of mainland China and around the world. The World Health Organization (WHO) declared a Public Health Emergency of International Concern on 30 January 2020, and a pandemic on 11 March 2020. Multiple variants of the virus have emerged and become dominant in many countries since 2021, with the Alpha, Beta, and Delta variants being the most virulent. As of 20 October 2021, more than 241 million cases and 4.91 million deaths have been confirmed, making it one of the deadliest pandemics in history.
Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), also known as the coronavirus, is the virus that causes COVID-19, the respiratory illness responsible for the ongoing COVID-19 pandemic. The virus was previously referred to by its provisional name, 2019 novel coronavirus (2019-nCoV), and has also been called human coronavirus 2019. First identified in the city of Wuhan, Hubei, China, the World Health Organization declared the outbreak a Public Health Emergency of International Concern on 30 January 2020, and a pandemic on 11 March 2020. SARS‑CoV‑2 is a positive-sense single-stranded RNA virus that is contagious in humans. As described by the US National Institutes of Health, it is the successor to SARS-CoV-1, the virus that caused the 2002–2004 SARS outbreak.
The COVID-19 pandemic in the United States is part of the worldwide pandemic of coronavirus disease 2019. Since January 2020, 45,132,148 confirmed cases have been reported with 728,192 deaths, the most of any country, and the twentieth-highest per capita worldwide. As many infections have gone undetected, the Centers for Disease Control and Prevention (CDC) estimated that, as of May 2021, there could be a total 120.2 million infections in the United States, or more than a third of the total population. COVID-19 is the deadliest pandemic in U.S. history; it was the third-leading cause of death in the U.S. in 2020, behind heart disease and cancer. From 2019 to 2020, U.S. life expectancy dropped by 3 years for Hispanic Americans, 2.9 years for African Americans, and 1.2 years for white Americans. These effects have persisted as U.S. deaths due to COVID-19 in 2021 exceeded those in 2020.
The COVID-19 pandemic in the United Kingdom is part of the worldwide pandemic of coronavirus disease 2019. The virus reached the UK in late January 2020. As of 13 October 2021, there have been 8,581,278 confirmed cases and 139,265 deaths among people who had recently tested positive – the world's 22nd highest death rate by population, and with the most overall cases and second-highest death toll in Europe after Russia. There has been some disparity between the outbreak's severity in England, Scotland, Wales and Northern Ireland – health-care in the UK is a devolved matter. Each constituent country has its own publicly-funded healthcare system operated by devolved governments.
A COVID‑19 vaccine is a vaccine intended to provide acquired immunity against severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), the virus that causes coronavirus disease 2019 (COVID‑19). Prior to the COVID‑19 pandemic, an established body of knowledge existed about the structure and function of coronaviruses causing diseases like severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). This knowledge accelerated the development of various vaccine platforms during early 2020. The initial focus of SARS-CoV-2 vaccines was on preventing symptomatic, often severe illness. On 10 January 2020, the SARS-CoV-2 genetic sequence data was shared through GISAID, and by 19 March, the global pharmaceutical industry announced a major commitment to address COVID-19. The COVID‑19 vaccines are widely credited for their role in reducing the spread, severity, and death caused by COVID-19.
"Cluster 5", also referred to as ΔFVI-spike by the Danish State Serum Institute (SSI), is a variant of SARS-CoV-2, the virus that causes COVID-19, that is believed to be extinct. It was discovered in North Jutland, Denmark, and is believed to have been spread from minks to humans via mink farms. On 4 November 2020, it was announced that the mink population in Denmark would be culled to prevent the possible spread of this mutation and reduce the risk of new mutations happening. A lockdown and travel restrictions were introduced in seven municipalities of North Jutland to prevent the mutation from spreading, which could compromise national or international responses to the COVID-19 pandemic.
Covaxin is an inactivated virus-based COVID-19 vaccine developed by Bharat Biotech in collaboration with the Indian Council of Medical Research.
The Alpha variant, also known as lineage B.1.1.7, is a variant of SARS-CoV-2, the virus that causes COVID-19. One of several variants of concern, the variant is estimated to be 40–80% more transmissible than the wild-type SARS-CoV-2. It was first detected in November 2020 from a sample taken in September in the United Kingdom, and began to spread quickly by mid-December, around the same time as infections surged. This increase is thought to be at least partly because of one or more mutations in the virus' spike protein. The variant is also notable for having more mutations than normally seen.
Beta variant, also known as lineage B.1.351, is a variant of SARS-CoV-2, the virus that causes COVID-19. One of several SARS-CoV-2 variants believed to be of particular importance, it was first detected in the Nelson Mandela Bay metropolitan area of the Eastern Cape province of South Africa in October 2020, which was reported by the country's health department on 18 December 2020. Phylogeographic analysis suggests this variant emerged in the Nelson Mandela Bay area in July or August 2020.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), has many variants; some are believed, or have been believed, to be of particular importance due to their potential for increased transmissibility, increased virulence, or reduced effectiveness of vaccines against them.
Gamma variant, also known as lineage P.1, is one of the variants of SARS-CoV-2, the virus that causes COVID-19. This variant of SARS-CoV-2 has been named lineage P.1 and has 17 amino acid substitutions, ten of which are in its spike protein, including these three designated to be of particular concern: N501Y, E484K and K417T. This variant of SARS-CoV-2 was first detected by the National Institute of Infectious Diseases (NIID) of Japan, on 6 January 2021 in four people who had arrived in Tokyo having visited Amazonas, Brazil, four days earlier. It was subsequently declared to be in circulation in Brazil. Under the simplified naming scheme proposed by the World Health Organization, P.1 has been labeled Gamma variant, and is currently considered a variant of concern.
The following is a timeline of the COVID-19 pandemic in the United States during 2021.
The term variant of concern (VOC) for severe acute respiratory syndrome coronavirus 2 is a category used when mutations in Receptor Binding Domain (RBD) substantially increase binding affinity in RBD-hACE2 complex, while also being linked to rapid spread in human populations.
Theta variant, also known as lineage P.3, is one of the variants of SARS-CoV-2, the virus that causes COVID-19. The variant was first identified in the Philippines on February 18, 2021, when two mutations of concern were detected in Central Visayas. It was detected in Japan on March 12, 2021, when a traveler from the Philippines arrived at Narita International Airport in Tokyo.
Kappa variant is a variant of SARS-CoV-2, the virus that causes COVID-19. It is one of the three sublineages of Pango lineage B.1.617. The SARS-CoV-2 Kappa variant is also known as lineage B.1.617.1 and was first detected in India in December 2020. By the end of March 2021, the Kappa sub-variant accounted for more than half of the sequences being submitted from India. On 1 April 2021, it was designated a Variant Under Investigation (VUI-21APR-01) by Public Health England.
Lineage B.1.617 is a lineage of SARS-CoV-2, the virus that causes COVID-19. It first came to international attention in late March 2021 after the newly established INSACOG performed genome sequencing on positive samples throughout various Indian states. Analysis of samples from Maharashtra had revealed that compared to December 2020, there was an increase in the fraction of samples with the E484Q and L452R mutations. Lineage B.1.617 later came to be dubbed a double mutant by news media.
Lambda variant, also known as lineage C.37, is a variant of SARS-CoV-2, the virus that causes COVID-19. It was first detected in Peru in August 2020. On 14 June 2021, the World Health Organization (WHO) named it Lambda variant and designated it as a variant of interest. It has spread to at least 30 countries around the world and is known to be more resistant to neutralizing antibodies compared to other strains. There is evidence that suggests the Lambda variant is both more infectious and resistant to vaccines than the Alpha and/or Gamma variant.
Epsilon variant, also known as CAL.20C and referring to two PANGO lineages B.1.427 and B.1.429, is one of the variants of SARS-CoV-2, the virus that causes COVID-19. It was first detected in California, USA in July 2020.
COVID-19 vaccine clinical research is the clinical research on COVID-19 vaccines, including their efficacy, effectiveness and safety. There are 24 vaccines authorized for use by national governments, with six vaccines being approved for emergency or full use by at least one WHO-recognised stringent regulatory authority; and five of them are in Phase IV. 204 vaccines under clinical trials that have not yet been authorized. There are also nine clinical trials on heterologous vaccination courses.
The Mu variant, also known as lineage B.1.621 or VUI-21JUL-1, is one of the variants of SARS-CoV-2, the virus that causes COVID-19. It was first detected in Colombia in January 2021 and was designated by the WHO as a variant of interest on August 30, 2021. The WHO said the variant has mutations that indicate a risk of resistance to the current vaccines and stressed that further studies were needed to better understand it. Outbreaks of the Mu variant were reported in South America and Europe. The B.1.621 lineage has a sublineage, labeled B.1.621.1 under the PANGO nomenclature, which has already been detected in more than 20 countries worldwide.
|journal=(help) The study in Israel tracked 46035 unvaccinated recovered and 46035 vaccinated people of the same age distribution, to compare their infection occurrence in the follow-up period. 640 infections and 21 hospitalization in the vaccinated group and 108 infections and 4 hospitalizations in the recovered group were recorded.
Collectively, our study reveals that antibody evasion of B.1.617 may contribute to the rapid spread of this variant... ...The RBD of the B.1.617 S protein harbors two mutations associated with (L452R) or suspected (E484Q) of antibody evasion... ...Moreover, E484K present the B.1.351 and P.1 variants confers antibody resistance (Li et al., 2021) and one could speculate that exchange E484Q might have a similar effect.
The reproduction number across influenza seasons and countries lied in the range 0.9–2.0 with an overall mean of 1.3, and 95% confidence interval (CI) 1.2–1.4.
The median of the R0 mean estimate for the ongoing epidemic (overall) is 1.78 (interquartile range: 1.44, 1.80)
A number of researchers have estimated the basic reproduction number by fitting models to the initial growth of epidemics in a number of countries. Their observations indicate that the SARS-CoV is less transmissible than initially thought with estimates of Ro in the range of 2-4.
The Delta variant is now in more than 111 countries and we expect it to soon be the dominant COVID-19 strain circulating worldwide, if it isn’t already.
New Zealand reported 35 new cases of COVID-19, bringing the number of current infections to 107.
The strict level 4 lockdown across New Zealand has been extended as the country's Delta outbreak climbs to more than 100 cases.
Tests by the National Public Health Centre (NNK) showed the presence of the Delta variant of the coronavirus in 14 new cases and the gamma variant in one new case, the prime minister's chief of staff said on Thursday.