Wuhan and Lombardy: Covid-19 Dynamics

As I write this, confirmed Covid-19 case count has passed the 420,000-mark recording close to 19,000 casualties. China still leads the case count chart despite being successful in containing the disease within its boundaries. Overtaking China by the US and Italy in terms of confirmed Covid-19 cases, clearly, is a matter of time.

Among many puzzles surrounding Covid-19, the most important is finding out the parameters needed to calibrate the epidemic curve. While more statistics are available than we had for many other diseases, the usefulness of these numbers is limited due to various non-medical interventions that were implemented from time to time in various countries and regions.

In fact, understanding the dynamics of the disease spread is vital to evaluate the efficacy of these non-medical interventions, many are already skeptical of. Many western governments have already followed China and implemented various measures that would cause huge damages not only to the economy and the society but also to the health of people. Needless to say that the cost of cure shouldn’t exceed the cost of disease. Therefore, it is of paramount importance to estimate the cost of the disease as accurately as possible and as early as possible.

One huge mistake often done is comparing countries ignoring their relative sizes. For example, the number of cases per one million of population in China is only 56 while the same number for Italy is now a staggering 1,114. This comparison, however, is highly misleading. The Chinese number is diluted heavily by its 1.4 billion population compared to the 60 million living in Italy. Therefore, I wanted to focus on Wuhan, the original epicenter of the disease and Lombardy, the current epicenter.

Wuhan has a population of 11,081,000 spread in 3,280 square miles. In Lombardy region 10,078,000 individuals are spread in 9,206 square miles. Even though Wuhan has a denser spread of its population compared to the Lombardy region the two places are comparable in terms of their population. Over 50,000 of the Covid-19 cases identified in China were reported within Wuhan. That amounts to 4,509 cases per one million of population. As of now the total number of confirmed cases in Lombardy region is 30,703 which represent 44.4% of the case count in Italy. That translates to 3,502 cases per one million of population. This shows that the situation in Lombardy can be worse even under the extreme assumption that none of the non-medical interventions in Wuhan were effective.

Wuhan was locked down on January 23 and by the end of next day 572 cases have been reported within the area. The number increased rapidly to reach 19,558 on February 11, nineteen days after the lock down. On February 12, Chinese authorities started to count clinically diagnosed cases too, in addition to the cases confirmed through laboratory testing. As a result, the case count jumped to 32,994. Around the same time, the epidemic curve was seen to hit its peak and the new cases started to drop. By mid-March, Wuhan was practically free from the disease.

It has been reported that the first Covid-19 cases in Wuhan were observed in late December. If so, the span of the epidemic curve was 80 days with its peak observed after around 40 days. Not clear is how the curve changed due to non-medical interventions. In addition to that, the numbers before February 12 are inaccurate. Underreporting is a common problem with Covid-19 statistics in all regions due to limited testing facilities and self-selection into testing even when testing facilities were not a constraint. The case in Wuhan, however, is something beyond this “usual” underreporting and we need to pay attention to this when we compare these numbers with statistics from any other region.

The first Covid-19 cases in Lombardy were reported on February 21 when 15 cases were confirmed. Probably, there was a delay in identifying these first cases but that can’t be a long one. It’s reasonable to assume that the epidemic curve in Lombardy lags that of Wuhan by approximately 40 days.

By end of March 24, there were 3,052 confirmed Covid-19 cases in Lombardy per million. On February 12, just after starting to count clinically diagnosed cases, the number of Covid-19 cases per million in Wuhan was 2,978. The density of identified Covid-19 cases in Lombardy region is now close to the number in Wuhan 41 days ago.

Can we expect that the curve for Lombardy to behave as Wuhan did with a 41 days lag? If so, Lombardy has now already passed its peak and the number of new cases should start to decrease gradually in coming days. The total number of cases in Lombardy should converge to around 45,500 by the third week of April. If this happens so, the policies implemented in Wuhan have been no more effective than the policies implemented in Lombardy. If the number of cases in Lombardy continues to rise surpassing this number, the difference will represent the effect of the policies implemented by Chinese authorities.