Why is the death rate of new coronary pneumonia difficult to determine?

  Of the people infected by the new coronavirus, how many will die? To be honest, it is not easy to give an exact figure, especially because the death rate will vary depending on the medical conditions and handling of the epidemic.
  So, can you give an estimate? On March 17, 2020, the World Health Organization said: “Globally, the death rate of new coronary pneumonia is about 3.4%.”
  This data is correct, but please don’t get me wrong. This is just a theoretical death rate, not The real death rate. The death rate is defined as the number of deaths divided by the number of confirmed cases. However, in theoretical calculations, the death toll is only counted as the number of people who have died, not including those who are not dead but who may still die. Therefore, the mortality rate obtained in this way is lower than the real situation. But on the other hand, because many mild patients may not be diagnosed, the number of confirmed diagnoses may be underestimated, so the theoretical mortality rate may be higher than the real situation. It can be seen that there are great uncertainties in both the numerator and denominator in the calculation of mortality.
  In addition, the death rate of new coronary pneumonia is also related to the age composition of the population. Age is an important factor in determining mortality. This is because the immune system of the elderly is low, and most of them suffer from chronic inflammation, which can speed up the replication of the virus. According to data from my country, the death rate begins to rise from around 50 years old, reaching 15% over 80 years old. This also means that for countries with an aging population, the mortality rate will be higher. Recently, Italy has become the country with the highest mortality rate outside China, which is closely related to the country’s severe aging of the population.