The pandemic is receding in the worst hot spots. Will it last?

LONDON – A month ago the pandemic looked grim. More than 750,000 cases of coronavirus have been recorded worldwide in a single day. Infections have jumped across the United States. New variants identified in the UK, Brazil and South Africa threaten the rest of the world.

But the past month has brought a surprisingly rapid, albeit partial, turnaround. New cases have halved at their peak globally, largely thanks to steady improvements in some of the same places that have weathered devastating epidemics this winter.

Cases are an imperfect measure, and uneven records and testing obscure the scope of outbreaks, particularly in parts of Africa, Latin America and South Asia. But fewer patients are presenting to hospitals in many countries with the highest infection rates, giving experts confidence the drop is real.

“It’s a great moment of optimism, but it’s also very fragile in many ways,” said Wafaa El-Sadr, 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 lull of many of the world’s worst epidemics creates a crucial opportunity to keep the virus on the decline as vaccinations begin to take effect. Experts say vaccines have done little to slow most epidemics so far, but a small group of countries, mostly wealthy ones, plan to vaccinate vulnerable groups by spring.

With the positive signs come a number of caveats and risks.

Many countries are still struggling. Brazil is battling a serious resurgence in the face of a new variant discovered in the country. Hospitalizations in Spain are higher than ever before, although official counts show a drop in new cases. And in a number of European countries – the Czech Republic, Estonia and Slovakia – the infection rate is worsening.

More contagious variants – or simply loopholes in social distancing and other control measures – could still lead to new spikes in infections that could outweigh the positive effects of the vaccination. A variant first discovered in Britain is spreading rapidly in the United States, and it has been implicated in outbreaks in Ireland, Portugal and Jordan.

And while most countries have seen a drop in cases over the past month, the overall global reduction has been largely attributable to just six countries with huge epidemics.

There is no single cause behind the slowdowns and the factors can differ in different locations. Public health experts in worst-affected countries attribute the progress to a combination of increased adherence to social distancing and mask-wearing, seasonality of the virus, and a build-up of natural immunity among groups with high rates. high levels of existing infection.

Each factor may not be sufficient on its own. Natural immunity, for example, would be well below the levels required to stop the epidemic. But the factors can combine to slow the speed of the virus spread.

While the United States has not imposed a national lockdown, voluntary behavioral changes, along with a degree of immunity in hard-hit communities, may have helped prevent an even worse outcome after the holidays. , said Caitlin Rivers, an epidemiologist at Johns Hopkins University. .

“During the winter when things were really bad, I think people saw how bad things were in their community and made different choices,” said Dr. Rivers. “They canceled gatherings, they stayed more at home, they looked for the mask, and these things are really helping, to set up, to reduce transmission.

The decline in South Africa has had many causes, but the main driver has been the sheer intensity of the infection rate last month, said Marc Mendelson, head of infectious diseases and HIV medicine at the University of Cap.

“At some point the virus hits a barrier because it cannot find new people to infect, and it cannot continue to increase its transmission,” he said.

British experts attribute the decline to a strict national lockdown put in place after the holiday season. Vaccines don’t explain it: even though a quarter of the population has been vaccinated, only the first recipients had significant protection as of January 10, when cases started to decline. These first doses were mainly intended for health workers and elderly patients already in hospital.

And some of the worst epidemics across the Americas, southern Africa and Europe peaked during or just after the holidays, said Dr. El-Sadr, a researcher at Columbia University. “In those few months, there have been all these opportunities for people to mingle, mingle and travel with their family and friends. I think that’s also probably the source of this surge.

The challenge of limiting infections until vaccines take effect will be considerably greater in countries with slower immunization programs.

Vaccinations had not started at all in 130 countries at the start of this month, according to the World Health Organization, and more than three-quarters of vaccine doses given were in just 10 countries. Many rich countries are piling up doses, ordering enough to vaccinate their residents multiple times, while poorer countries have yet to receive any.

And a finding from South Africa that the AstraZeneca vaccine had little effect on a fast-spreading variant dealt another blow to countries that planned to rely on the relatively cheap and easy-to-store vaccine. as part of their deployment.

“We’re just starting our vaccination campaign in South Africa, and it’s going to be incredibly slow and far from where we wanted to be right now,” Dr Mendelson said. “For countries that have vaccines, it’s a slightly different landscape.”

Experts believe vaccines will play a critical role in reducing infections, preventing hospitalizations and deaths, and even reducing the risk of future mutations if countries are able to immunize large parts of their populations. But the next period will be critical to avoid a new wave of infection.

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