Unraveling the mystery of Europe’s uneven covid surges

A year ago this week, the European Union banned nonessential travel from outside the bloc, as the first coronavirus wave caused increasing havoc on the continent. In Italy, Europe’s initial epicenter, cases had already begun to spiral, which other countries took as a grim portent.

But the wave broke unevenly, smashing, pulling back and surging again into different countries at different times, in a confounding sequence experts are still scrambling to untangle.

More than a year into the pandemic, as some countries struggle yet again with surging cases, it still often seems there is little rhyme or reason to which countries get hit hardest, and when.

In the Czech Republic, just a half day’s drive from the Italian border, the expected wave didn’t arrive last spring. The country was hailed as a European success story. In Prague, people held a street party in July to say “farewell” to the virus.

Months later, case numbers spiked. In the space of a few weeks in fall, the Czech Republic went from being one of the least affected countries in Europe to the most.

Despite more than a year of study, experts are not sure how to explain why countries in the same region saw such drastically divergent outbreaks at different times. But they have developed theories — sometimes only to see them turned on their heads.

“I think what we’re looking at is something that is highly multidimensional,” said Maarten van Smeden, a medical statistician at University Medical Center Utrecht in the Netherlands. “

The virus hits hardest among the elderly and in densely populated areas. Measures such as shutdowns and border closures play a role in determining the spread. In some places, vaccines have begun to have an impact. In parts of Europe and elsewhere, variants are driving new surges.

But these factors tell only part of the story.

The early first wave

After the initial coronavirus outbreak in Wuhan, China, in late 2019, it didn’t take long for the virus to reach Europe.

On Jan. 31, 2020, two Chinese tourists in Rome tested positive. A cluster of cases were detected in Lombardy and Veneto on Feb. 21. The first death was recorded the next day. By March, Italy had imposed Europe’s first lockdown.

The initial seeding of the virus in Europe may have been stochastic, said Francois Balloux, director of the University College London’s Genetics Institute, which means the first cases dotted the continent at random.

“If you have thousands of introductions at the same time, the risk is that none of them go extinct and you get overwhelmed,” he said.

As travelers returning from conferences and ski vacations crossed borders, the virus made its entrance to new countries in a barrage of separate initial transmissions. Balloux said that the minimum estimate for the number of cases introduced to Britain in March is 1,000. The first outbreaks to balloon may simply be a matter of dumb luck.

Last spring, the virus was surging across much of Western Europe. With hospitals overwhelmed, deaths spiked. By May, Belgium had the highest mortality rate in the world among confirmed cases, at 16.4 percent.

But the country may not have been as much of an outlier as it appeared.

Belgium took pains to record all covid-19 deaths, while other countries had less exact accounts, and across Europe differences in testing availability led to disparities in the accuracy of case counts. “

“Everybody records things at least a little bit differently. And this was particularly bad in the first wave,” said Rowland Kao, a professor of veterinary epidemiology and data science at the University of Edinburgh in Scotland.

“This is the ugly summary of dirty data,” Van Smeden said, “and a virus that is not very easily modeled.”

The deferred first wave

While the virus wrought havoc across Western Europe in the spring, some countries saw only limited outbreaks.

Germany recorded its first cases in January and a sizable outbreak in Baden-Württemberg state the following month, but was able to delay the bulk of its initial surge, shutting borders and imposing lockdowns in some states. By April, Chancellor Angela Merkel praised “fragile intermediate success,” and some restrictions were lifted.

For Van Smeden in the neighboring Netherlands, the difference appeared stark. “If you’d have asked me at the start of the pandemic, I’d have said the Germans are just much better” in their response, he said.

But it wasn’t so simple. Sweden, which took a controversial, relaxed view of restrictions, also had avoided much of the initial worst effects of the wave. But after summer, both countries saw cases climb.

In hindsight, it appears that neither Germany’s strict measures nor Sweden’s laissez faire restrictions protected them from an eventual onslaught. But why were they spared, in relative terms, in the spring? “The real issue is that we don’t seem to know,” Van Smeden said.

The latecomers

[Some countries that avoided initial coronavirus surge see first spike in cases]

Prague residents declared an end to the crisis in July. The Czech Republic, a country of 10 million, has recorded just 12,000 infections.

But within a few months, cases soared. By mid-October, the country reported 492 new cases per 100,000 people over seven days, according to a Washington Post analysis, suggesting one of the fastest-escalating outbreaks in the world.

The Czech Republic wasn’t unique: In Europe, a noticeable geographic split between east and west had begun to emerge.

At the time, there seemed to be links to policy decisions. Many countries that had shut down initially had relaxed measures as case numbers subsided in summer. In countries including the Czech Republic, Poland and Hungary, lockdowns became a political issue for right-wing governments.

“As the months dragged on, populist leaders responded to public pressure to reopen economies and societies, and sure enough, the virus found its way in,” Judyth Twigg, a professor at Virginia Commonwealth University who specializes in global health, told The Post at the time.

[Biden’s promise of widespread vaccinations by summer prompts frustration in slower-moving Europe]

Often, the waves that hit countries such as the Czech Republic and Poland that avoided an initial surge were even deadlier for the lack of even a low percentage of immunity in the population, according to some experts.

“We’re nowhere near herd immunity, but there does seem to be some reduction in the number of cases because of more immune people,” Kao said of Britain, adding that in some areas of the country more than a third of the population may have some level of immunity.

And while real progress has been made in some countries — in large part because of successful immunization programs, with rollouts unfolding at different speeds across the continent — countries that saw early spikes and later ones alike are battling the spread of more transmissible variants.

Cases are surging again in the Czech Republic, Hungary and Poland that missed last spring’s wave, but also in Italy.

Estimates from the Economist Intelligence Unit indicate that most of Europe is expected to reach widespread vaccination coverage before the end of the year. But the virus may still continue to spread, and could thrive in poorer parts of the world for years.

More waves could lie ahead. “One fundamental, underlying driver of these waves is seasonality,” Balloux said. “It’s very typical behavior for the flu rhinoviruses or the other four coronaviruses; they have highly seasonal peaks.”

In the future, however, the waves may be smaller — what Balloux dubs “wavelets.” Exactly how and where these will hit is hard to say, he adds, but “we’ve been through the worst now in most places.”

Maps by Atthar Mirza. Photo editing by Chloe Coleman.