Brazilian Coronavirus: Withdrawal of covid-19 in Amazon’s Manaus raises herd immunity issues

The hospital system was fragmented. Coronavirus The patient was turned back. The basic necessities-beds, stretchers, oxygen-were exhausted. There was no place to take patients in the ambulance. People died at home. The grave digger could not catch up.

The destruction of humans at doctor Manaus, Brazil, was “catastrophic” and feared by doctor Gerald Felipe Barbosa.

But then, unexpectedly, it began to settle down, without the interventions found elsewhere.

[These neighbors were hospitalized with coronavirus. Their vastly different journeys show the depths of Brazil’s rich-poor divide.]

Hospitalizations for patients with coronavirus plummeted from more than 1300 at the peak in May to less than 300 in August. Excess deaths in Manaus have been reduced from about 120 per day to virtually zero. The city closed the field hospital.

In countries hit by the new coronavirus, more than 3.6 million people were infected and more than 114,000 were killed. This reversal surprised frontline doctors. Manaus never imposed the blockades and other strict containment measures successfully adopted in Asia and Europe. And many people ignored what policies existed.

In the spring, Amazon cities have become a global symbol of devastation, where diseases can spread in developing countries. But now it’s back to near normal-much faster than many expected-scientists and public health officials are asking why. The question is part of a broader discussion between scientists and public health officials about the mechanism of herd immunity and the level of transmission that must be overcome before the disease begins to recede.

[Brazil reports record infections as coronavirus spreads to all regions]

The stricken European cities have begun to resume without breaking the second wave. Scientists are cautious in Guayaquil, a large Ecuadorian city where the body is left on the streets Guess Reached its collective immunity. Some researchers are now Suggest the same About New York City.

The factors that help keep the virus away from Manaus and other cities remain unknown. Changed behavior and individual community characteristics certainly play a role. Manaus has done much more testing than before. But whatever is dynamic, scientists and health officials are beginning to wonder if the early prognosis for herd immunity may have exceeded standards.

Initially, it was thought that 60-70% of the population needed to develop antibodies to reach collective immunity. However, Guayaquil does not break 33 percent. Manaus, the capital of the state of Amazonas, never exceeds the age of 20.

“Manaus is certainly an interesting case,” said Jarbas Barbosa da Silva, Assistant Director of Pan American Health Organization. “The hypothesis—this is just a hypothesis—is that the peak in Manaus is so strong that the spread of infection from the community may have caused some collective immunity.”

[Video and photos show Brazil’s Bolsonaro defied health guidelines before testing positive for the coronavirus — and after]

Drakonia’s restrictive measures will significantly reduce the disease, said Barcosa. But in Manaus, the decline is gradual, with a steady progression of new cases continuing daily. The curve suggests that the disease was following “natural forces,” Barbosa said.

Manaus said he “paid a very high fee” to get there. During the spring it killed three times more than usual. In total, the 2 million cities along the Amazon River filled about 3,300 more people than usual.

“This was not a strategy,” said Barbosa. “It was a tragedy.”

“It was totally unexpected”

The concept of collective immunity has long been used to justify and explain the purpose of mass vaccination campaigns. Scientists factor in the prevalence of the disease, or how many people a single sick person gets, to determine the percentage of people who should be vaccinated. In the case of particularly infectious diseases such as measles, it reaches 95%. For others, it’s low.

However, researchers say that collective immunity functions differently during life development. Even if you exceed the magic number, this disease will not disappear. Instead, shrinking the pool of potential victims slows down transmission until it disappears. Containment policies can further reduce infection. However, an explosive resurrection is unlikely once the pool of potential victims reaches critical mass, whether or not they are hired. Too many people will have this disease.

“In Italy, it hit the Milan area badly,” said Tom Briton, a mathematician at Stockholm University. “But Rome is not so much. If I had to bet money on the second wave, I would bet all money on Rome, not Milan.”

[Brazil, ravaged by the coronavirus, becomes key testing ground for vaccine]

Briton and other researchers are studying what is known as “susceptibility heterogeneity.” Early herd immunity models, and vaccination campaigns, have worked on the assumption that everyone is the same. But individuals vary. Some are socially active while others are physically vulnerable. Heterogeneity reduces the proportion of infections in which herd immunity can be achieved, according to the researchers. Those who are sick and most likely to be transmitted-the most socially active and most susceptible-get caught first. But once they are out of the pool of potential victims, the risk is less for everyone else.

“Their immune effects will be greater,” Briton said.

In a paper published in Science in June, he and other researchers Estimation The heterogeneity of the population reduces the coronavirus herd immunity to 43%. Others say it may be low.

Gabriella Gomez, a mathematician at Strathclyde University in Glasgow, scrutinized the European cities overwhelmed by the disease. To paper Writing with nine other researchers who have not been peer-reviewed, she has come to the astonishing conclusion: herd immunity may be lower than 20 percent.

“Without immunity, we would have expected cases to start increasing soon after the intervention was lifted,” she said. “That’s what we were saying at the time. “It’s too early to lift the intervention. The incident will begin.” But it wasn’t. And in most cases, they continued to fall. It was totally unexpected. “

[Brazil ignored the warnings. Now, while other countries fret over a second coronavirus wave, it can’t get past its first.]

But the stakes are very high, killing more than 800,000 people worldwide, and the virus is still unknown. Many researchers are reluctant to say whether they believe that the worst has already ended in some of the most devastating cities. No one knows how long your immunity will last. The virus can mutate.

Jeffrey Sherman, an environmental health scientist at Columbia University, said: “I love it too, but the reality is that it is a wishful observation. It’s a confirmation bias. You can’t pick the evidence you want to be true. This is your face very quickly. We need to be very careful about this, as it can explode.”

Cautious optimism

Manaus doctor Pietropinheiro Alves knows how quickly it can happen. Despite being physically separated from the rainforest, Manaus is one of the most international cities in Brazil. Attracted to the free trade zone, companies around the world are rooted in Amazon. As the coronavirus spread throughout the world, strains from China, Europe and the United States were soon distributed and disappeared.

It didn’t take long for the surge of patients to overwhelm the hospital system.

“People are dying at home,” in the worst of circumstances, Pinheiro Alves cried the phone in early May. “They can’t get help at the hospital.”

He felt hopeless. People were still crowded in the street. Authorities did not want to impose a blockade. In many poor Manaus, which are already in crisis, the mayor said it would lead to social turmoil and violence. So Pinheiro Alves spent his rest time locating the ventilator.

“We fought for social isolation,” said Manaus Mayor Arthur Virgilio Neto.

“The attempt failed,” he said. “There was no real social isolation. People were still out, and somehow didn’t understand why. At the most difficult time, I went to a field hospital and was caught in a traffic jam,” Why People don’t go home? What are they doing?”

Doctor Uildéia Galvão saw the results. Every day, ambulances line up outside the central Manaus hospital, each with a patient in need of a bed. Sometimes they sat for hours and waited for someone to die before letting go of the bed.

[In Brazil, a dying man and a desperate search for an open bed]

Depending on how high the city is, there will be three or four. And one day it was two days. then.

“It was the first sign that the number of emergency calls was declining,” said Galvão.

The intensive care unit is starting to empty. Emergency coronavirus calls slowed, dropping from 2,410 in April to less than 180 in July. The screams of the ambulance stopped. Some scientists said the victory was visible.

“Why Manaus will be the first Brazilian city to beat the Covid-19 epidemic,” wrote a group of researchers at the Federal University of Amazonas.

Street activities have returned to pre-pandemic levels. People flocked to the river to swim and have a party. Attractiveness of wearing a mask: Widely ignored. A private school opened. Then publish it. The cases continued to grow to hundreds of people each day, but far fewer were serious enough to justify hospitalization.

“There is no specific explanation,” said Henrik Dos Santos Pereira, a scientist at the Federal University of Amazonas. Maybe there is an invisible biological immunity. Or the city’s relative youth stopped the worst.

[As coronavirus kills indigenous people in the Amazon, Brazil’s government goes missing]

“The problem is that we don’t know how many people are vulnerable,” said Dos Santos Pereira. “At first I thought it was everyone, but I don’t think the whole world is susceptible…. that is what causes us to reconsider the theory of herd immunity.”

Mayor Virgilio wants scientists to be right. The Manaus medical system once failed. If the second wave comes, he has little doubt what will happen.

“Our ability is overwhelming.”

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