Coronavirus : Update 13 from the Epicenter

Posted by in Coronavirus

So, when can we relax the lockdown and get the global economy started again?

Well, first of all, every country is on its own trajectory, so there’s no single answer to that question, but let’s look at Italy and extrapolate from there. ..

What we really need to know is “have enough people been infected for us to have acquired any level of herd immunity?” Back in Update 6 we discussed the true number of infections in Italy at the time the lockdown was announced on March 9th. We calculated half a million, verses the published figures of 9,172. Had the epidemic been left free reign, that number would have doubled every few days, however, the lockdown ‘flattened the curve’ and slowed the infection rate non-linearly – making predictions extremely difficult.

Once the peak of an exponential epidemic is past then it becomes easier to make calculations, and Italy passed the peak in terms of deaths a few days ago :

If the rate of change in the number of deaths in Italy continues on its current trajectory, we’ll be close to zero daily deaths within three weeks. The numbers in orange are not official projections – just my best guess :

From total fatalities we can back-calculate total infections following the logic in this study published in The Lancet. They estimate the average global mortality rate to be 1.38% and report that it remains fairly stable between countries. This is far lower than the 12% generally reported in Italy, because it considers the entire pyramid of untested infected people :

At the top of the pyramid, those meeting the WHO case criteria for severe or critical cases are likely to be identified in the hospital setting, presenting with atypical viral pneumonia. These cases will have been identified in mainland China and among those categorised internationally as local transmission. Many more cases are likely to be symptomatic (ie, with fever, cough, or myalgia), but might not require hospitalisation. These cases will have been identified through links to international travel to high-risk areas and through contact-tracing of contacts of confirmed cases. They might also be identified through population surveillance of, for example, influenza-like illness. The bottom part of the pyramid represents mild (and possibly asymptomatic) cases. These cases might be identified through contact tracing and subsequently via serological testing

The graphs predict total deaths in Italy to be about 24,350. If they represent 1.38% of those infected, then total survivals (tested and un-tested) will be about 1.73 million, which is only about 3% of the population – far below the 60% required for herd immunity.

However, we should consider the discussion from Update 9 during which we took a look at the distribution of cases and fatalities across the nation and found wild disparities in terms of numbers and mortality rates. The reality is that 76% of all deaths in Italy are confined to just 3 regions : Lombardia, Emilia Romagna, and Piemonte :

…and of course not every region has the same population, so we end up with a tiny cluster of regions with more significant levels of immunity, and the rest of the country where the vast majority of people are still susceptible. This is similar to Berlin in Germany, London in the UK and NY in the US :

The scale here is logarithmic, with only Lombardia reaching 10% immunity

Still, it doesn’t look like we’re close to actionable community immunity levels anywhere in Italy. This conclusion matches the objective results of a study done on a town in norther Germany where carnival was celebrated and social distancing regulations were ignored. A significant Covid-19 outbreak followed, however subsequent rigorous testing showed only 14% of the town’s population finally contracted the disease.

Add to this, the fact that early surveys are showing anomalies in antibody development for those who survived an infection, and it’s clear that for at least 90% of us in some regions (and ~100% in many) we will be still be ‘at risk’ – protected not by herd immunity, but only by our closed borders :

A team from Fudan University analysed blood samples from 175 patients discharged from the Shanghai Public Health Clinical Center and found that nearly a third had unexpectedly low levels of antibodies, and not sufficient to guarantee protection against reinfection. In 10 cases, antibodies could not be detected at all. Fortunately his phenomenon appeared to be skewed towards the younger, healthier patients. Severe illness in the elderly generated a stronger acquired immune response.

Still, with curves flatlining, the Italian government has announced that certain additional businesses (children clothing stores, computer production, forestry supplies) will be able to open on Tuesday 14th April as long as they are able to observe social distancing and sanitary guidelines during operation. I would expect the rest of the country to follow in early May.

Every country’s timeline is slightly different as the graph above shows, but with some exceptions the overall picture is likely to match Italy’s – a tragic death toll but little to show for it in terms of acquired immunity. What is sure is that seeing the lockdown through to the end at least gives a country the chance to catch its breath and restart commercial activity – albeit under the umbrella of ongoing restrictions to movement and social contact. Jump the gun and the epidemic will restart.

There remain open a couple of key unknowns :

  1. Can we expect a second wave of? If so, what will provoke it?
  2. If it comes, will it hit hard like the 1918 Spanish Flu, and what can we do to prepare?
UK fatalities during 3 waves of the Spanish Flu

We’ll look at those questions next time.

Stay safe, stay resolute, and stay positive.