In February, health-care workers and epidemiologists in India puzzled over their good fortune. Coronavirus case counts had gone down, demand for ventilators was manageable and experts predicted that the country would be spared a major second wave.

In April, events have taken a different turn. Images that have gone viral on social media show bodies heaped in makeshift crematoriums. Hospital beds and oxygen are scarce. Desperate patients and relatives have turned to the black market for medicine, while others die in hospitals amid oxygen shortages. Recent days have seen repeated record infection figures, which are likely undercounts. The death toll from the virus surpassed 200,000 on Wednesday, as India again reported a record number of fatalities and experts cautioned that those numbers, too, were an underestimate.

As the pandemic surges — and as hospitals buckle under the strain — some have blamed their government, and the wider world, for failing to stem the cataclysmic spike.

Here’s what you need to know about the coronavirus surge in India:

How did the outbreak get so bad?

That question continues to puzzle experts. Back in early February, hospitalization numbers had plummeted, and India was reporting about as many new cases per day as New York state, despite being 50 times as populous. The only likely explanation was widespread immunity, epidemiologists said at the time.

India is now the epicenter of the global pandemic and a focal point of international concern. The country reported more than 350,000 new cases on Monday alone, breaking daily infection records for the fifth straight day.

Experts are starting to think that immunity in India may not have been as widespread as previously believed. Some scientists argue that earlier waves of infections primarily affected the poor, but the current surge is reaching wealthier people who had just started socializing again after staying home during the first wave.

Large group gatherings may have also played a role: Indian Prime Minister Narendra Modi has been criticized for lifting virtually all restrictions and holding massive political rallies, and a religious festival that drew tens of thousands of Hindu pilgrims from all over the country has been linked to more than 100 cases.

“There was a public narrative that India had conquered covid-19,” Ramanan Laxminarayan, an epidemiologist in Princeton University, told Nature. People also began to relax more after India launched its vaccination campaign in January, he added. As a result, many let their guard down and went back to socializing, traveling and holding large weddings.

Are new variants making the situation worse?

It is not yet clear if the presence of highly infectious new variants is the key factor that made India’s outbreak go from bad to worse. Scientists generally agree that it is likely that these variants played a role, but how much of a role is up for debate.

What we do know is that the variant B.1.1.7, which was first identified in the United Kingdom, is now the dominant variant in the Indian state of Punjab. That is significant because multiple studies have found that B.1.1.7 is between 40 percent to 70 percent more contagious than earlier iterations of the virus, and also appears to be more lethal.

Another variant, B. 1.617, has become the dominant variant in the state of Maharashtra, according to Nature. That variant is sometimes referred to as the “double mutant” variant because it contains two key mutations that were found in two other highly infectious strains. So far, however, there is no hard data that suggests that B. 1.617 is more transmissible than other variants, and India does not perform enough genome sequencing to determine whether B. 1.617 is driving the current outbreak.

Variants first identified in Brazil and South Africa have also been identified in India, the country’s Ministry of Health and Family Welfare said last month.

What has the government done about it?

India is making coronavirus vaccines available to anyone over age 18 starting May 1. It is also curbing the number of coronavirus vaccines that it exports and focusing on distributing those doses to citizens.

Some cities and states have announced new lockdown restrictions, including curfews and bans on travel and nonessential activities. Modi, meanwhile, has said that lockdowns should be a last resort and declined to institute one nationwide.

With hospitals in India turning away patients and supplies running low, young tech-savvy volunteers are providing salvation for some. (Reuters)

Modi’s administration is sending oxygen tankers on “Oxygen Express” trains to parts of the country that are facing urgent shortages, and freeing up military stockpiles of medical equipment. Armed forces have been deployed to hospitals. But the government has also ordered social media platforms to take down critical posts that call attention to the catastrophic state of affairs in India, which many see as a case of misplaced priorities.

Why are there oxygen shortages?

Typically, India’s hospitals and medical clinics use only about 15 percent of the liquid oxygen produced in the country. Recently, however, nearly 90 percent of the country’s total supply has been diverted to health-care facilities, Rajesh Bhushan, a senior health official, told the BBC.

Since some Indian states do not have plants where they can produce their own liquid oxygen, they have to wait for supplies to be trucked in from other parts of the country. Filling up an oxygen tanker takes two hours, according to the BBC, which has led to lengthy lines outside oxygen plants. Once full, the tankers can only drive at 25 mph and travel during daylight hours.

As demand soars in crowded hospitals, some critics say that the government should have been better prepared. In October, India’s health ministry announced a plan to build more oxygen plants, but so far only 33 out 162 have been constructed. Modi announced plans for another 551 oxygen plants — one for each district — on Sunday. The prime minister has ordered that those “be made functional as soon as possible,” a news release from his office stated, but it may already be too late for many of the patients who are dying due to oxygen shortages at hospitals across India right now.

“We have been telling authorities that we are willing to increase our capacity, but we need financial aid for that,” Rajabhau Shinde, who runs a small oxygen plant in Maharashtra, told the BBC. “This should not have happened. As the saying goes, dig the well before you’re thirsty. But we didn’t do that.”

How has the world responded?

Countries across the world have stepped up to help.

Singapore, Germany and the United Kingdom dispatched oxygen-related materials to India over the weekend. France, Russia and Australia will send medical aid, and China and Pakistan have offered help.

The European Union is coordinating with member states to provide oxygen and medicine, and World Health Organization Director General Tedros Adhanom Ghebreyesus said Monday that the WHO would send additional staff and supplies to India.

As other countries offered aid, pressure mounted over the weekend for the United States to do more.

On Sunday, the Biden administration said it would send raw vaccine materials, ventilators, personal protective equipment, oxygen-related supplies and therapeutic medicines to India. It is also mobilizing an American “strike team” of health experts, as well as funding for “a substantial expansion” of Indian vaccine manufacturing capability.

In a phone call with Modi on Monday, Biden pledged to support India’s efforts to beat back the virus surge. The White House also announced Monday that the United States will share up to 60 million doses of the Oxford-AstraZeneca coronavirus vaccine with other countries after they undergo a safety check — a process that could take weeks or months. It is unclear how many of those doses will go to India.

Awash in vaccines, the United States has faced criticism for hoarding doses and maintaining policies that have curbed the export of vaccines and raw materials. Doctors Without Borders praised the United States’ decision to donate Oxford-AstraZeneca doses in a statement Monday evening, but urged the U.S. government to demand that pharmaceutical companies “share technologies and know-how” with manufacturers across the world. Pharmaceutical companies have rebuffed such requests.