NEW DELHI — India overtook Brazil to become the country with the second-highest number of coronavirus cases in the world as infections continue to accelerate in this country of more than 1.3 billion people.

India added 90,802 cases — a fresh global record in the pandemic — in the last 24 hours, pushing its total past 4.2 million. Only the United States, with 6.2 million cases, has recorded more. Brazil had 4.1 million cases as of Sunday evening.

More than 71,000 people in India have died of covid-19, the disease caused by the novel coronavirus, making it the worst-affected nation in Asia.

Unlike the United States and Brazil, where the number of new cases have eased in recent weeks, India’s outbreak shows no sign of peaking. Since early August, India has been reporting the highest daily increases in cases in the world.

Infections have spread from major cities to every corner of the country, including to rural areas that are poorly equipped to test and treat patients.

Earlier this spring, India instituted the world’s largest lockdown to try to stem the pandemic. But the restrictions caused economic devastation and failed to reverse the trajectory of the outbreak. In early June, the government changed course.

Jayaprakash Muliyil, a leading Indian epidemiologist, predicted that India’s daily reported cases will continue to rise in coming weeks. He estimates that the daily cases could double over the next month before retreating.

He criticized the government for implementing a harsh nationwide lockdown, calling it a “waste” that hurt the economy and people’s livelihoods. The lockdown “was a cruel joke played on our poor in the name of covid,” he said.

Now, nearly all the prior shutdown measures have been lifted, although schools remain closed and large gatherings are still prohibited. On Monday, the subway system in New Delhi, India’s capital, started transporting passengers again for the first time in more than five months.

As the country has reopened, coronavirus cases have surged. Testing has also expanded significantly, although the number of tests remains low on a per capita basis compared to other countries.

The coronavirus is only one of several battles India is fighting. Crippled by the lockdown, India’s economy shrank by 24 percent in the second quarter over the same period a year earlier, the largest drop ever recorded and the worst contraction of any major economy.

Meanwhile, India is also grappling with a major crisis on its border with China. In June, the two countries engaged in their deadliest clash in nearly 50 years. Thousands of troops from both countries remain deployed at the disputed frontier and talks have failed to lower tensions.

Indian government officials say that as testing increases, so too will cases. They point out that India fares well compared to some countries on measures of mortality from the coronavirus. India has recorded about 50 deaths per million people due to covid-19, far lower than in either Brazil or the United States, where the same figure is more than 500.

Experts believe that India’s lower death toll may be partly the result of its predominantly youthful population. Others speculate that some immunological factor might be making the disease less severe. The official figures also understate the true death toll, because an unknown number of deaths from covid-19 are being missed or misreported.

Some doctors caution that India’s outbreak is entering a more dangerous phase as the virus spreads to smaller towns and villages. Containing and addressing coronavirus cases “is going to be much more difficult and challenging” in such areas, said SP Kalantri, a professor of medicine at the Mahatma Gandhi Institute of Medical Sciences. Health-care infrastructure is weak, access to medical care is difficult and diagnostic tests are lacking, he said.

“If this trend continues,” Kalantri said, “the worst is yet to come.”