Many theories have been developed to model epidemics mathematically, and Tangente has previously reported on them. But much remains unknown about the virus behind the current epidemic, SARS-CoV-2, which belongs to the coronavirus family. The fact that some people, including children, may be asymptomatic carriers obscures crucial data, such as the number of people who have been infected and subsequently become immune.
Models have been developed to study how the pandemic spreads through a given region. But because so little was known about the disease, the initial results did not really match observations on the ground.
As early as January 24, Vittoria Colizza's team at Inserm (Institut national de la santé et de la recherche médicale) presented a study estimating the risk that the epidemic would be imported into Europe. It drew on passenger flows before lockdown from affected regions of China to major European cities, estimating the probability that a passenger was carrying the virus and would transmit it upon arrival.
Data needed for the models -------------------------------
The distribution of cases over time produces an "epidemic curve." Its shape can reveal certain features: a curve with a peak followed by a downward phase is characteristic of a point source of infection. A "plateau" indicates a persistent source. A curve with several "waves" points to person-to-person transmission.