Since the start of the epidemic, researchers have been able to establish that it is the elderly who contract the severe forms of Covid-19. But are they also more likely to be infected by the virus? Japanese epidemiologists provide some answers.
Japanese epidemiologists have questioned whether susceptibility to infection varies with age and whether it has a role to play in the current epidemic. For this, they created a mathematical model, the results of which are published in .
Susceptibility to infection does not vary with age
Scientists first used to understand if susceptibility to infection alone could explain the distribution of mortality observed in three countries, Japan, Italy and Spain. These three countries were chosen because they publicly shared their epidemiological data.
According to their model, we can explain the distribution of mortality only with the susceptibility, but this is dependent on the R0, the reproduction rate ofcalculated at a time T of the epidemic. Now the R0 the three countries for the period under review, last May, are quite different. The R0 is between 2.4 and 3.3 for Italy; for Japan, it is 1.7 and 2.9 for Spain. The death rate (number of deaths per 100,000 inhabitants) communicated was also different: 382.3 for Italy; 507.2 for Spain and 13.2 for Japan.
Despite these differences, the distribution of mortality by age group is comparable between the three countries. The researchers conclude that susceptibility to infection does not vary with age. Despite everything, this does not completely rule out that the elderly are more susceptible to infection, but if it is, it does not seem to have a significant influence on the number of patients affected by Covid-19.
Although susceptibility does not seem to vary with age, the severity of the disease, the appearance of symptoms and the mortality are, for their part, well related to the age of the patients. the most important with and the existence of chronic illnesses prior to infection.