Thousands of migrant workers are fleeing Bangladesh’s capital Dhaka to escape an imminent lockdown and a surge in Covid-19 cases linked to the Delta variant that is threatening to overwhelm health systems.

Authorities are imposing curbs, including a ban on public transport from Monday, ahead of a “complete” nationwide lockdown for seven days from Thursday that will bar all but essential activity. Security forces will be deployed to enforce the rules.

A wave of infections fuelled by the Delta variant has wreaked havoc in south Asia since it erupted in India this year. The latest surge is believed to have seeped into Bangladesh through the neighbours’ extensive land border.

Bangladesh is reporting more than 5,000 cases a day and on Sunday recorded its highest official Covid-19 death toll of 119. The national test positivity rate is at 22 per cent, according to the Dhaka Tribune.

But experts question the official figures, which they say fail to capture the full extent of the surge. Public health experts warn that neglected health systems across swaths of the country — including border districts and poor rural areas — have already been overwhelmed.

“Not all district hospitals have ICUs,” said Mushtaque Chowdhury, convener of civil society group Bangladesh Health Watch and a public health professor at Columbia University, forcing sick patients to travel long distances for treatment. “There’s an overflow of people seeking admission . . . There’s huge pressure.”

While Bangladesh had introduced other lockdowns, Chowdhury said they had been ineffectually enforced.

“There’s no choice [this time]. We have to implement this very strictly and enforce it if we’re to contain the disease, which is just getting worse and worse.”

India faced a catastrophic wave of Covid-19 infections in April and May linked to the Delta variant, sparking the country’s worst crisis in decades as it swamped health systems in both rural and urban areas. While cases have fast receded, India is still recording about 50,000 new infections a day.

Nepal was also plunged into crisis by a surge in cases as migrants returned from India.

Bangladesh’s National Technical Advisory Committee on Covid-19 last week warned that health systems were at grave risk without robust measures to halt transmission of infections.

Complicating matters is Bangladesh’s sluggish vaccination drive, with only about 3 per cent of the population fully immunised. The country was initially dependent on Indian-made Oxford/AstraZeneca jabs, and was forced to find alternatives after its neighbour stopped exporting shots.

Bangladesh is now procuring jabs from China and Russia, as well as through the World Health Organization’s Covax programme.

But the prospect of tough lockdown restrictions in a country where millions live in poverty has prompted alarm about the potentially dire economic and humanitarian consequences.

Over the weekend migrant labourers thronged ferry terminals in Dhaka — one of the world’s largest urban areas with more than 20m people — to return to their rural homes and avoid being stuck in the city without jobs. Chowdhury said this exodus risked turning into a “super spreader” event if the labourers were carrying the virus.

“I am heading home. What would we do during this lockdown? It’s better to starve with my family in the village,” Mohammad Masum, a migrant worker, told Agence France-Presse while waiting for a ferry.