India registered a record 412,262 new coronavirus infections on Thursday and a record 3,980 daily death toll, as a second wave of infections overwhelms the healthcare system and spreads from cities into the vast countryside.

Health ministry data show that COVID-19 cases in the world’s second most populous nation have increased past 21 million, with a death toll of 230,168.

With hospitals scrabbling for oxygen and beds in response to the spike in infections, the World Health Organization said in a weekly report that India accounted for almost half the COVID-19 infections reported worldwide last week and a quarter of the fatalities.

India’s actual tally could be 5 to 10 times the official figures, according to medical experts.

India’s coronavirus crisis has been most acute in the capital, New Delhi, among other cities, but in rural areas – home to around 70% of India’s 1.3 billion people – limited public healthcare is posing more challenges.

“The situation has become dangerous in villages,” said Suresh Kumar, a field coordinator with Manav Sansadhan Evam Mahila Vikas Sansthan, a human rights charity.

In some villages where the charity works in the northern state of Uttar Pradesh – home to nearly 200 million people – “there are deaths in almost every second house”, he said.

“People are scared and huddled in their homes with fever and cough. The symptoms are all of COVID-19, but with no information available many think it is seasonal flu.”

The country’s top scientific adviser has warned of a potential third wave of infections.

The government’s principal scientific adviser, K. VijayRaghavan, told a news briefing on Wednesday that “phase 3 is inevitable, given the high levels of circulating virus.”

“But it is not clear on what time scale this phase 3 will occur… We should prepare for new waves.”

The spike in COVID-19 cases has also coincided with a dramatic drop in vaccinations due to supply and delivery problems, despite India being a major vaccine producer.