How Europe's second wave is proving less deadly than the first

New coronavirus cases in Europe are now eclipsing the daily totals seen when the pandemic first took hold - and yet a surge in deaths from the disease has not followed in the second wave's wake.

Last week European countries together announced 41,000 fresh cases a day on average, which is not only 28,000 more than the best week in July - right before the second wave of infections hit the continent over the summer - but five thousand more than the worst week of April.

Deaths, on the other hand, remain relatively low. There were on average just 360 deaths announced each day across Europe last week, which stands not too far from a low of 274 in July and is dwarfed by a peak of 4,012 in April.

One explanation for this discrepancy could be the fact that coronavirus deaths tend to lag infections by nearly a month, with a recent review by Public Health England reporting that around 88 per cent of deaths from Covid-19 in the UK occurred within 28 days of a positive test.

But even when this lag is accounted for, Telegraph analysis shows that the number of so-called 'at risk' cases in Europe has  now climbed rapidly to over 30,000 a day - a rate on par with that seen at the beginning of the pandemic.

This chart - and its clear second upswing - stands in marked contrast to a chart of daily new deaths in Europe, the line of which only indicates a small uptick in deaths from the summer onwards, in contrast to the sharp spike in the spring, when coronavirus cases last rose to this extent.

A way to express this relationship between confirmed cases and deaths is through a measure known as the case fatality ratio (CRF), which Telegraph analysis has found to be falling both across Europe and within the UK.

At the start of July around 2.4 per cent of confirmed cases were leading to deaths, but in the most recent few weeks the rate has fallen to around 1.4 per cent.

This decline is even more stark in the case of the UK, where the case fatality ratio has fallen from around 6 per cent at the beginning of July to around 1 per cent.

However, the CRF can only tell us so much - it doesn't account for the possibility of  confirmed cases becoming more or less severe.

Hospital occupancy beginning to climb

Given an average of 28 days from diagnosis to death in fatal cases, and the likelihood of hospitalisation among those cases, the best measure to typically watch after cases rise is the hospitalisation rate.

It's the best indicator of whether deaths are likely to follow, or whether the new cases being detected are less severe.

For weeks hospital wards have been largely free of Covid patients compared to the most difficult days of the pandemic, implying less serious or asymptomatic cases have been those being picked up.

But many European countries are now beginning to see a reversal of that trend, with upticks in hospital occupancy rates of those with Covid-19.

Though the levels are not yet a cause for concern, the rise indicates new cases are becoming more severe.

Younger cases driving rise - but beginning to spread

One of the main factors behind the low death rates as the second wave of infections begins to cement itself across the continent is they have largely been contained among the young.

After the first wave decimated care homes and tore through the most vulnerable, most new infections have been detected in younger age groups as lockdowns lift and communities return to work, pubs and other people's homes.

According to data from Public Health England's (PHE) surveillance reports, the rate of confirmed cases among 20 to 29-year-olds in England are now at rates similar to those seen at the height of the pandemic in the country - at 46 per 100,000.

It has risen 169 per cent in four weeks, up from 17.1 per 100,000 in the week ending August 6.

It is a fraction of the rate of confirmed cases among older populations at its peak, which reached 232 per 100,000 among the over 80s in the week ending April 5.

But new cases are beginning to leak into the more vulnerable communities as people continue to mingle - a reason to urge caution.

The rate among the over 80s has risen 65 per cent in two weeks, from 7.8 to 12.9 per 100,000, after weeks of decline.

A similar picture is emerging among the 70 to 79 age group, almost doubling from 3.7 to 7.3 cases per 100,000 - the highest level since late June.

If the virus continue to cross generations and age groups, it increases the chance deaths will follow.

And according to the latest data on hospitalisations, the rates are slowly beginning to climb, albeit still significantly below the levels seen when the virus first peaked.

At the outset of the pandemic, health professionals had to contend with a new, unknown virus, so the number of deaths as a proportion of hospital occupancy was significantly higher - peaking at around 5.4 per cent in the early days of the virus' spread.

As doctors became better at treating the disease that rate fell dramatically, down to around 0.8 per cent in late August.

In recent days the rate has begun to climb once more, up to 1.3 per cent according to the latest data from PHE.