THE Delta variant is already the dominant strain of Covid-19 in the US, according to data modelling done by the US Centers for Disease Control and Prevention (CDC).
According to the health agency's estimates, the Delta variant became dominant in the country over the two weeks ended July 3, with 51.7 per cent cases linked to the variant that was first identified in India.
The proportion of cases linked to the Alpha variant which was first identified in Britain and had been dominant in the US so far, fell to 28.7 per cent.
The data, which shows the estimated biweekly proportions of the most common SARS-CoV-2 lineages circulating in the United States, is based on sequences collected through CDC's national genomic surveillance since December 20, 2020.
The Delta variant, which is becoming dominant in many countries, is more easily transmitted than earlier versions of the coronavirus and may cause more severe disease, especially among younger people. It has now been found in every US state, health officials have said.
On Tuesday (6), US President Joe Biden encouraged Americans who have not yet been vaccinated against Covid-19 to get their shots to protect themselves from the widely spreading, highly contagious variant.
So far, preliminary data has shown that vaccines made by Pfizer Inc and BioNTech, AstraZeneca and Moderna are largely protective against Delta, with the concentration of virus-neutralizing antibodies being somewhat reduced.
















Activists and supporters of the Cockroach Janta Party (CJP) clash with police personnel during a protest demanding the resignation of India's Education Minister Dharmendra Pradhan over alleged NEET examination irregularities in New Delhi on July 20, 2026. India's riot police baton-charged protesters in New Delhi as they tried to march to parliament on July 20, escalating a protest over irregularities in major examinations.Getty Images
A police personnel fires tear gas shells to disperse activists and supporters of the Cockroach Janta Party (CJP) during a protest demanding the resignation of India's Education Minister Dharmendra Pradhan over alleged NEET examination irregularities in New Delhi on July 20, 2026. India's riot police baton-charged protesters in New Delhi as they tried to march to parliament on July 20, escalating a protest over irregularities in major examinations.Getty Images
Protesters gather as they take part in a demonstration organised by the Cockroach Janta Party (CJP) at Jantar Mantar during the opening day of Parliament's Monsoon Session on July 20, 2026 in New Delhi, India. A mix of protesters gathered in New Delhi on Monday as discontent bubbled over myriad issues, and as Sonam Wangchuk, an activist who was fasting in protest, was forcibly taken to hospital on Sunday. Getty Images
Opposition leaders of the Indian National Congress (INC) party Rahul Gandhi (C back) and his sister Priyanka Gandhi Vadra (C) stage a sit-in protest calling for Prime Minister Narendra Modi's resignation outside the latter's residence in New Delhi on July 21, 2026, a day after police crackdown against the protesting Cockroach Janta Party (CJP) supporters demanding the Education Minister Dharmendra Pradhan step down over alleged NEET examination irregularities.Getty Images
Protesters stand amid debris strewn across a road during clashes with police at a demonstration organised by the Cockroach Janta Party (CJP) on the opening day of Parliament's Monsoon Session on July 20, 2026 in New Delhi, India. A mix of protesters gathered in New Delhi on Monday as discontent bubbled over myriad issues, and as Sonam Wangchuk, an activist who was fasting in protest, was forcibly taken to hospital on Sunday.Getty Images