Experts say Indian coronavirus variant 'may not be as contagious as thought'

Surge could be linked to 'founder effect', where a small number of people infect a higher proportion than normal

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  Health workers talk to attendants of a patient at a hospital meant for treating COVID-19 patients in New Delhi, India. AP

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  An Indian doctor displays collected samples before conducting COVID-19 routine testing at a hospital in Bangalore, India. EPA

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  Members of the Mira Bhayander Municipal Corporation (MBMC) fire brigade spray disinfectant at residential areas during the coronavirus emergency lockdown in Mira Road near Mumbai. EPA

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  An Indian health official gives a nasal swab to his colleague inside a COVID-19 mobile testing van before collecting samples from people, as India remains under an unprecedented extended lockdown. Getty

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  People stand inside marked circles maintaining social distancing to get groceries distributed by police personnel during a government-imposed nationwide lockdown in Faridabad. AFP

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  A worker sprays disinfectant on a gas station during a government-imposed nationwide lockdown as a preventive measure against the Covid-19 coronavirus, in Siliguri. AFP

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  A girl reacts as a doctor wearing protective gloves takes a swab from her to test for the coronavirus disease at a residential area in Ahmedabad, India, Reuters

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  President of Tejendra Swaha Sahai Sakhi Mandal women's association, Varshaben Mali checks the quality of facemasks made for Ahmedabad Municipal Corporation. AFP

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  Indian paramilitary soldiers patrol a closed wholesale market in the old quarters of Delhi during a nation wide lockdown to control the spread of the coronavirus in New Delhi, India. AP

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  A man gets his body temperature checked as he queues to receive relief material during a lockdown in Kolkata. AFP

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  People queue to receive relief material during a government-imposed nationwide lockdown, Kolkata. AFP

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  A man cleans his hands with sanitiser before collecting relief material during a government-imposed nationwide lockdown, in Kolkata. AFP

The Indian variant of Covid-19 may not be as transmissible as first thought, according to some experts.

The B1617.2 strain, a sublineage of a new variant of concern, is growing rapidly in the UK, as it did in India, where it was first detected.

However, some scientists said the surge may actually be the result of a phenomenon called the "founder effect".

That happens when a small number of people infect a higher proportion than normal.

Experts suspect this is because cases are increasing in the UK in areas with high numbers of large, multi-generational households but are now levelling off in some parts.

Prof Carl Heneghan, director of the Centre for Evidence-Based Medicine at the University of Oxford, said numbers were “falling off at speed” in India.

"We could be looking at a founder effect and where you've got a small number of people having a bigger impact," he told The Telegraph.

“India is actually looking more like the natural curve which happens in winter and has a high drop-off, as opposed to flattening the curve.”

Speaking from Downing Street on Wednesday evening, Prof Jonathan Van-Tam, the UK's deputy chief medical officer, said that the additional transmissibility fell within in a wide range.

"We have a credible range which goes from a few per cent through to 50 per cent more transmissible," he said.

"I think most people feel it’s going to be in the middle, but it is just too early."

Opinion divided over strength of variant

Other experts, however, do not agree, citing models that suggest the strain has a significant growth advantage.

Tom Wenseleers, a biology and biostatistics professor at KU Leuven in Belgium, said the latest data showed B1617.2 was still "spreading like wildfire and outcompeting the Kent variant, B117".

He pointed to a model which showed the Indian variant had a growth advantage of 11 per cent a day over the Kent strain.

“Assuming a constant and unaltered generation time of 4.7 days, a growth advantage of 10 per cent a day would translate to a 60 per cent transmission advantage,” he wrote on Twitter.

He said that could be because of several reasons.

“In practice, a mix of increased contagiousness, longer duration of infectiousness and/or some immune escape could explain this growth advantage. This remains to be studied further.”