Wealthy countries in Europe and North America hit first by the pandemic are training armies of contact tracers to hunt down cases, designing tracking apps and planning virus-free air travel corridors.

In many poor regions in the developing world, where crowded slums and streets mean even basic measures like hand-washing and social distancing are difficult, the coronavirus is exploding now that restrictions are being removed.

Last week, Brazil, Mexico, South Africa, India and Pakistan all saw one-day records of new infections or deaths as they reopened public spaces and businesses without detailed surveillance and testing system in place.

Boys wearing protective masks to help curb the spread of the coronavirus, look out the window of a train at a railway station, in Karachi, Pakistan, Saturday, Jan. 6, 2020. (AP Photo/Fareed Khan)

Boys wearing protective masks to help curb the spread of the coronavirus, look out the window of a train at a railway station, in Karachi, Pakistan, Saturday, Jan. 6, 2020. (AP Photo/Fareed Khan)

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Clare Wenham of the London School of Economics described the situation in Brazil as “terrifying,” noting the government’s decision to stop publishing a running total of COVID-19 cases and deaths.

“We’ve seen problems with countries reporting data all over the world, but to not even report data at all is clearly a political decision,” she said. That could complicate efforts to understand how the virus is spreading in the region and how it’s affecting the Brazilian population, Wenham said.

Cemetery workers in a protective gear shovel dirt over the gravesite of a COVID-19 victim at the Panteón de San Lorenzo Tezonco Iztapalapa cemetery, in a section for victims of the new coronavirus, in the Iztapalapa neighborhood of Mexico City, Tuesday, June 2, 2020. Mexico is passing through the pandemic’s most critical moment with a dramatically increasing number of confirmed and suspected infections. (AP Photo/Marco Ugarte)

Cemetery workers in a protective gear shovel dirt over the gravesite of a COVID-19 victim at the Panteón de San Lorenzo Tezonco Iztapalapa cemetery, in a section for victims of the new coronavirus, in the Iztapalapa neighborhood of Mexico City, Tuesday, June 2, 2020. Mexico is passing through the pandemic’s most critical moment with a dramatically increasing number of confirmed and suspected infections. (AP Photo/Marco Ugarte)

Johns Hopkins University numbers showed Brazil recorded more than 36,000 coronavirus deaths Monday, the third-highest in the world, just ahead of Italy. There were nearly 692,000 cases, putting it second behind the U.S.

Rio de Janeiro allowed surfers and swimmers back in the water but small numbers of beach-goers were defying a still-active ban on gathering on the sand.

Relaxing restrictions “is dangerous because we’re still at the peak, right? So it’s a little dangerous,” said Alessandra Barros, a 46-year-old cashier on the sidewalk next to Ipanema Beach. “Today it’s calm, but this weekend will be crowded.”

Workers move the body of a COVID-19 victim to the crematorium inside the Panteón San Nicolás Tolentino cemetery in the Iztapalapa neighborhood of Mexico City, Tuesday, June 2, 2020. Funeral parlors and crematoriums in Iztapalapa, a borough of 2 million people, say they have seen their work multiplied with the surging number of dead of COVID-19 in the capital's hardest-hit corner by the new coronavirus. (AP Photo/Marco Ugarte)

Workers move the body of a COVID-19 victim to the crematorium inside the Panteón San Nicolás Tolentino cemetery in the Iztapalapa neighborhood of Mexico City, Tuesday, June 2, 2020. Funeral parlors and crematoriums in Iztapalapa, a borough of 2 million people, say they have seen their work multiplied with the surging number of dead of COVID-19 in the capital's hardest-hit corner by the new coronavirus. (AP Photo/Marco Ugarte)

Loosened coronavirus lockdowns could ultimately have devastating consequences, health experts warn.

“Politicians may be desperate to get their economies going again, but that could be at the expense of having huge numbers of people die,” said Dr. Bharat Pankhania, an infectious diseases expert at the University of Exeter in Britain.

He said re-imposing recently lifted lockdown measures would be equally dangerous.

Indian Muslims offer prayers after Jama Mosque opened after lockdown in New Delhi, India, Monday, June 8, 2020. India is reopening its restaurants, shopping malls and religious places in most of its states after a more than 2-month-old lockdown even as the country continues to witness a worrying rise in new coronavirus infections. (AP Photo/Manish Swarup)

Indian Muslims offer prayers after Jama Mosque opened after lockdown in New Delhi, India, Monday, June 8, 2020. India is reopening its restaurants, shopping malls and religious places in most of its states after a more than 2-month-old lockdown even as the country continues to witness a worrying rise in new coronavirus infections. (AP Photo/Manish Swarup)

“Doing that is extremely worrying because then you will build up a highly resentful and angry population, and it’s unknown how they will react,” Pankhania said. And as nearly every developed country struggles with its own outbreak, there may be fewer resources to help those with long overstretched capacities.

Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, said Monday the pandemic was “worsening” globally in under-developed regions with shaky health systems, noting that countries on Sunday reported the biggest-ever one-day total: more than 136,000 cases. Among those, nearly 75 percent of the cases were from 10 countries in the Americas and South Asia.

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Across Latin America, countries that cracked down early and hard, like El Salvador and Panama, have done relatively well, although some of that has come at the expense of human rights and civil liberties, Wenham said.

Disinfection team disinfect a classroom at Ivory Park Secondary School east of Johannesburg, South Africa, Thursday, May 28, 2020, ahead of the June 1, 2020, re-opening of Grade 7 and 12 learners to school.(AP Photo/Themba Hadebe)

Disinfection team disinfect a classroom at Ivory Park Secondary School east of Johannesburg, South Africa, Thursday, May 28, 2020, ahead of the June 1, 2020, re-opening of Grade 7 and 12 learners to school.(AP Photo/Themba Hadebe)

“Countries willing to take the short-term hit are the ones coming out better,” she said, adding that poor countries weren’t entirely without options, noting early, pre-emptive actions by Sierra Leone and Liberia.

“They learned from the Ebola outbreak and moved quickly when they decided their economy couldn’t cope with community transmission,” she said.

So far, numbers have been relatively low in both countries in West Africa.

Some experts say lockdowns were always “panic measures” and not designed to be sustainable, particularly in developing countries.

A health worker collects a sample from a man at a drive-through testing and screening facility for the coronavirus, in Islamabad, Pakistan, Saturday, June 6, 2020. (AP Photo/Anjum Naveed)

A health worker collects a sample from a man at a drive-through testing and screening facility for the coronavirus, in Islamabad, Pakistan, Saturday, June 6, 2020. (AP Photo/Anjum Naveed)

“The strategy has its roots in China, in the desire to eliminate the disease, but that clearly went out the window a couple of months ago,” said Mark Woolhouse, a professor of infectious disease epidemiology at the University of Edinburgh.

“Many countries are now deciding that the cure could turn out to be worse than the disease,” he said.

Woolhouse suggested that countries unable to lock down their populations could focus instead on targeted interventions to protect those most at risk, such as people over 60 or those with underlying medical conditions.

“Countries are simply not following World Health Organization advice to lock down and are saying they need another strategy,” Woolhouse said.

He noted the relatively younger demographics of many developing countries might help them avoid the high death rates seen in Italy, Spain and Britain.

An employee of a shop disinfects the showroom at a mall that reopened in New Delhi, India, Monday, June 8, 2020. India is reopening its restaurants, shopping malls and religious places in most of its states after a more than 2-month-old lockdown even as the country continues to witness a worrying rise in new coronavirus infections. (AP Photo/Shonal Ganguly)

An employee of a shop disinfects the showroom at a mall that reopened in New Delhi, India, Monday, June 8, 2020. India is reopening its restaurants, shopping malls and religious places in most of its states after a more than 2-month-old lockdown even as the country continues to witness a worrying rise in new coronavirus infections. (AP Photo/Shonal Ganguly)

Even tiny Panama, once Latin America’s fastest-growing economy, is struggling to maintain some of the region’s tightest controls amid simultaneous economic slowdown and disease spread.

“It’s impossible to maintain a quarantine for all of 2020,” said Dr. Xavier Sáenz-Llorens, a government adviser on the disease response. “The country would sink.”

The Associated Press contributed to this report.