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 11,081,000spread 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.

A partner in crime in facemasked China?

On Monday, the Chinese Centre for Disease Control and Prevention (CCDC) published the results of a study on COVID-19 outbreak analyzing all cases diagnosed as of February 11, 2020 in Mainland China. The total of 72,314 patient records analyzed included 44,672 confirmed cases, 16,186 suspected cases and 10,567 clinically diagnosed cases.

The demographic characteristics of the confirmed cases and the associated outcomes clearly shows the differential effect of the disease on various age groups. While 46.5% of confirmed cases represent patients younger than 40, only 6.3% of total deaths have been reported within that age group and only a single death below 20 was among those. On the other hand, those who are older than 60 represent only 31.1% of confirmed cases but 81.0% of total deaths. Why COVID-19 is hitting the elderly hard?

Until February 11, only the confirmed cases were associated with COVID-19 in official statistics but suddenly China started to count the clinically diagnosed cases too. With this change, the number of cases jumped up by nearly a third. A disease is what we define and so is the cause of death. When a definition changes, many healthy individuals become sick and vice versa. In November 2017, the US clinical guidelines on the threshold defining high blood pressure was lowered from 140/90 mm Hg to 130/80 mm Hg. Consequently, the percentage of US adults with hypertension increased immediately from 32% to 46%.

Economists explain life and death using the health capital model. In the widely used model introduced by Michael Grossman in 1972, individuals inherit an initial stock of heath that depreciates with age. They can invest in inputs such as medical care, diet, exercise and living environment to increase this stock while various diseases act as random shocks to decrease the stock of health capital. Death occurs when the stock falls below a certain minimum level.

Based on the Grossman model a disease can cause death when the initial endowments are very low, when most of the health stock has gradually depreciated or when the magnitude of an adverse health shock is very large. The COVID-19 does not appear to cause a huge health shock itself. Many people have mild symptoms and most of them recover easily. The fatality rate is very low among the young, so it can’t be due to low initial endowments. Most likely, COVID-19 can be the last fatal punch on those who have a limited residual stock of health capital.

COVID-19 does not kill itself. The immune response to the virus destroys lung tissue and cause inflammation ultimately cutting off the oxygen supply to the body causing death. Lung health of a person can deteriorate due to various other causes- smoking and air pollution are examples. Yet, when a person has been tested positive for COVID-19, we solely attribute that death to the virus.

In many media reports during the past month, we saw Chinese people with their faces covered with masks to protect themselves from COVID-19. Facemasks, however, are not new to most Chinese cities. At least for two decades, people living in smog-filled large Chinese cities have been routinely wearing facemasks to minimize the health risks of air pollution.

The great economic prosperity and urban growth in China during the recent past have also resulted in the deterioration of the quality of air in most parts of China, Beijing-Tianjin-Hebei and surrounding areas in particular. An assessment by the United Nations Environmental Programme (UNEP) just before the 2008 Summer Olympics in Beijing noted that addressing Beijing’s poor air quality was a top priority in planning for the Games. By that time health concerns among athletes and officials over air quality in Beijing had attracted wide international media coverage. Due to various regulatory measures implemented prior to the Olympic games by Chinese authorities, Beijing smog cleared after many years in 2008. These “Olympic Blues”, however, didn’t last long since most of the regulatory measures implemented were temporary.

China has been fighting air pollution aggressively since 2013 and a recent report by UNEP shows that annual average concentration of PM10 in Beijing has decreased by 55.3% during 1998-2017. Yet, Beijing’s ambient air still exceeds China’s air quality standards and the World Health Organization’s recommended “safe” levels. China still is one of the countries with most polluted air.

According to a study published in 2016 which analyzed the effects of temporary improvement in air quality in Beijing in 2008 on mortality, 285,000 premature deaths in urban China could be averted annually if PM10 concentrations were to decrease by 10 percent. Another study published in 2017 shows that that the air quality related deaths in China from stroke, ischemic heart disease and lung cancer increased from approximately 800,000 cases in 2004 to over 1.2 million cases in 2012.

As data show air quality in Wuhan and the surrounding area has been as poor as in Beijing during the past decades. If we go back to Grossman’s health capital model, this should have affected the health stock of most people living in this part of the country, particularly the elderly. When you just have a small health stock left, you don’t need a large shock to exhaust it. Is that what happened with COVID-19? If so, can we call COVID-19 the sole culprit? Is bad air quality in China a partner in crime?