The pandemic is receding into the worst hotspots. Will it last?

LONDON – A month ago, the pandemic looked bleak. More than 750,000 cases of coronavirus were discussed worldwide in one day. Infections have increased throughout the United States. New variants identified in the United Kingdom, Brazil and South Africa have threatened the rest of the world.

But the last month has brought a surprisingly rapid, if partial turnaround. New cases worldwide have declined to half their peak, driven mainly by steady improvements in some of the same places that have endured devastating outbreaks this winter.

Cases are an imperfect measure, and uneven records and tests hide the extent of outbreaks, especially in parts of Africa, Latin America and South Asia. But fewer patients show up in hospitals in many countries with the highest infection rates, giving experts the confidence that the decline is real.

“This is a great moment of optimism, but it is also very fragile in many ways,” said Wafaa El-Sadr, an epidemiologist at Columbia University’s Mailman School of Public Health. “We see the light at the end of the tunnel, but it’s still a long tunnel.”

The silence in many of the worst outbreaks in the world creates a critical opportunity to hold back the virus as vaccinations take effect. Experts believe that vaccines have so far done little to slow down most outbreaks, but a small group of countries, mainly affluent ones, plan to vaccinate vulnerable groups again by spring.

The positive signs involve a number of reservations and risks.

Many countries are still struggling. Brazil is struggling with a severe boom in light of a new variant being discovered in the country. Hospitalizations in Spain are higher than ever before, although official counts show a decline in new cases. And in a number of European countries – the Czech Republic, Estonia and Slovakia – the infection rate is getting worse.

More contagious variants – or just decay in social distance and other control measures – can still cause new infections that can outweigh the positive effects of vaccination. A variant first found in Britain is spreading rapidly in the United States and has been implicated in congestion in Ireland, Portugal and Jordan.

And while most countries have seen a decline in cases over the past month, the overall global decline has been driven primarily by just six countries with huge epidemics.

There is no single cause behind the slowdown, and the factors may differ in different places. Public health experts in the worst-affected countries attribute the progress to a combination of increased compliance with social removal and mask wearing, the seasonality of the virus and the build-up of natural immunity among groups with a high number of existing infections .

Each factor may not be enough on its own. For example, it is believed that natural immunity is much less than the levels needed to stop the epidemic. But the factors may work together to slow down the rate at which the virus spreads.

Although the United States has not instituted a national exclusion, voluntary behavioral changes coupled with some immunity in severely affected communities may have helped prevent a worse outcome after the holidays, said Caitlin Rivers, an epidemiologist. at Johns Hopkins University, said. .

“During the winter, when things got really bad, I think people saw how bad things were going in their community, and they made different choices,” said Dr. Rivers said. “They canceled the meetings, they stayed more at home, they stabbed at the mask, and these things really help reduce the transmission.”

The decline in South Africa had many causes, but the biggest cause was the infection rate last month, said Marc Mendelson, head of infectious diseases and HIV medicine at the University of Cape Town.

“At some point, the virus hits a barrier because it can not find new people to infect, and it can no longer continue to increase its transmission,” he said.

British experts attribute the decline to a strict national exclusion imposed after the holiday season. Vaccines do not explain this: Although a quarter of the population was vaccinated, only the earliest recipients had significant protection on January 10 when the cases there began to decline. These early doses mostly went to health workers and elderly patients who were already in the hospital.

And some of the worst outbreaks across the Americas, South Africa and Europe have peaked during or just after the holidays, says Dr. El-Sadr, a University of Columbia researcher. ‘For a few months there were all the opportunities for people to mingle, mingle and travel with family and friends. I think it probably caused that boom too. ”

The challenge of keeping infections until vaccines take effect will be significantly greater in countries with slower vaccination programs.

Vaccination has not yet started in 130 countries earlier this month, according to the World Health Organization, and more than three-quarters of the vaccine doses administered were in just ten countries. Many rich countries are stopping doses and ordering enough to repeatedly immunize their people, while poorer countries have not yet received them.

And a finding from South Africa that the AstraZeneca vaccine had little effect on a rapidly spreading variant dealt another blow to countries that intended to switch to the relatively inexpensive vaccine, which could be easily stored. rely.

“We have just started our vaccination campaign in South Africa, and it is going to be incredibly slow and not nearly where we wanted to be,” said Dr. Mendelson said. “For countries with vaccines, it’s a slightly different landscape.”

Experts believe that vaccines will play a critical role in preventing infections, preventing hospitalizations and deaths and even reducing the chance of future mutations if countries are able to vaccinate large sections of their population. But the next period will be critical to prevent another wave of infection.

“We have a small opportunity here to take advantage of the declining number of new infections,” said Bruno Ciancio, head of disease surveillance at the European Center for Disease Prevention and Control. “We need to continue with public health measures and vaccinate as many people as possible.”