Monday 23 March 2020

Covid-19 and Vitamin D – air pollution and mortality in Italy

Satellite image showing hot-spot of air pollution in northern Italy

The pandemic of Covid-19 is a serious world-wide problem at present. It is due to a coronavirus related to SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East acute Respiratory Syndrome), and like them it originated in animals.

Covid-19 started in the Chinese city of Wuhan. The spread of the virus in Wuhan was extremely rapid, but effective closure of the city minimised spread elsewhere in China. Air transport enabled the virus to spread rapidly world-wide.

The virus has caused major problems in Iran and in Europe, and within Europe Italy has suffered most in terms of disease and deaths.

It is deaths that are most important. It is easy to forget that in 1968-69, during period of only about two months, 80,000 people died in the UK alone as the result of the pandemic of what we call Hong Kong flu. I was working as a young doctor in the front line at that time. We were taken by surprise by the pandemic, and of course there were no intensive care units in those days.

In the present pandemic "cases" can include people who are ill and test positive for Covid-19, and people who are perfectly well and test positive. As testing becomes more widespread the number of "cases" will increase as more well people are tested.  The numbers of deaths will change more slowly.

Its is considered that:

Death rate (%) = Total deaths x 100 / Total cases

When the denominator (total cases) increases at a greater rate than the numerator (total deaths), the death rate will appear to reduce. This will be a misleading health indicator, and it is a mathematical aberration.

It is much better to use as a health indicator the total number of deaths as proportion of the total population, that is total deaths per million. This is generally robust, but in some nations, for example Switzerland, the resident population might be significantly higher than the official population.

I have constructed a spreadsheet to collect and analyse the data concerning Covid-19 in a number of countries. The data, up-to-date on March 23rd 2020, can be seen below.

The variations within Europe are particularly interesting. 

The death rate as proportion of "cases" who die is remarkable low in Ireland (0.4%), Germany, (0.4%) and Norway (0.3%). Is this due to a large number of well people who have tested positive? If not is it the result of exceptionally good medical services? Or perhaps a common factor that cannot yet be identified.

The same countries have a low number of deaths per million population, Ireland 0.8, Germany 1.3, Norway 1.3. The numbers are greater but still comparatively low. There seems to be a real factor in these countries responsible for the low mortality. 

The low mortality in Germany in particular has been discussed widely in the media but no explanation is forthcoming.

The UK is experiencing 4.9 deaths per million, and 84.2 cases per million, relatively low. Cases per million are much higher in Ireland (184.9), Germany (313.3). and Norway (441.7), but this could be a result of extensive testing of the well population. 

Numbers tested in different countries are available:

It can be seen that Norway has conducted far more tests per million population than other European countries. This will explain the high cases per million (441.7) with few deaths per million (0.3). The testing rates in Germany and Ireland are not exceptional.

The testing rate in Italy is second to Norway in the European countries shown, but Italy has an exceptional problem. The Italian people and the health services are struggling. To date there have been almost 60,000 cases and 5,500 deaths. This represents a 9.3% mortality of cases, and an astonishingly high 90.5 deaths per million population.

Many people in Italy have thought long and hard about why this is, as indicated to me by my friend Dr Luca Mascitelli. No explanation is at hand.

However, it is on the Lombardy plain in northern Italy that the epidemic has been most serious and with the highest fatality. The major city of Bergamo has been identified as the epicentre of the epidemic. An inspection of a pre-epidemic image of Europe identifies the Lombardy plain as the area of Europe with greatest air pollution.

Copernicus satellite image showing northern Italy, February 2020.

The Lombardy plain sits at the foot of the Alps, which rise very steeply on the south side. The River Po runs through the plain. The main cities are Bergamo and Milan. Turin is a short distance to the west, in Piedmont. It is a place of motor cars, and restrictions have been suggested in Milan in recent months. It is one of the areas in the world with the least wind.

Lombardy, Italy
The man pollutant detected by the Copernicus satellite has been nitrogen dioxide, but in general air pollution blocks the transmission of sunlight through the atmosphere to ground level. The sunlight is essential for the synthesis in the skin of Vitamin D from 7-dehydrocholesterol. After its activation in the liver and kidneys to Calcitriol, Vitamin D combines with and activates the Vitamin D Receptor enzymes in the cells, in turn switching on a chain of genetic events, stimulated at the DNA level by Vitamin D Response Elements that enhance T-cell activation and the defensive inflammatory cascade.

Activation of intracellular and genetic processes by vitamin D

Enhancement of defensive T-cell activation by vitamin D following micro-organism invasion

It is was established in the early years of the 20th century that vitamin D is essential not just for bone health but for defensive immunity. At that time it was the disease tuberculosis that was particularly important, and for which air quality was so critical. The immune suppression caused by lack of sunlight and vitamin D in the activation of tuberculosis, so obvious in industrial cities, was met again in the late 20th century during the epidemic of AIDS. This was another acquired immunodeficiency syndrome that led to activation of tuberculosis and other conditions.

It is no coincidence that Wuhan, China, also experienced very serious air pollution before the epidemic. Also, it is now the time of the year when immunity and body stores of vitamin D are at their lowest, and it has been noted that this is the time when tuberculosis is most likely to present as an illness. 

And so perhaps this is the explanation as to why northern Italy is suffering so badly at present.

A public health initiative should be to supply vitamin D in large bolus doses to the people of Italy, and other countries where death rates are high. In fact, it is what we all need to help with protection against Covid-19.

The pandemic in Germany is causing surprisingly few deaths. This, the German paradox, is the subject of the next Blog post:


  1. Vitamin D Supplementation Could Prevent and Treat Influenza, Coronavirus, and Pneumonia Infections
    To be updated by March 26, hopefully

  2. Former CDC Chief Dr. Tom Frieden: Coronavirus infection risk may be reduced by Vitamin D - March 23

  3. I must mention thanks for sharing such vital information. Acceptable daily exposure