R0 for SARS-COV-2: China lowest, Germany, Italy follow


Progress or decline of the Covid-19 epidemic is assessed by the R0 value, the average number of people infected by one infected person. Values known so far are: China (Wuhan) 0.1, Germany 0.7, Italy 0.8. A new generation of infected people according to the R0 value will appear roughly every week. The very small value from Wuhan indicates a rapid extinction of the virus to the point at which containment can be reasserted and any sporadic outbreaks suppressed. With its R0 around 0.8 Italy has only managed to halve the number of disease cases in the four weeks after the peak of infections. So to reduce the disease to a point at which sporadic outbreaks can be suppressed. say 100 cases a day, will take a further 11 weeks. And if the lockdown is loosened then things may go even slower.

The figure from Wuhan was revealed by Harvard Professor Xihong Lin to the Science and Technology Select Committee on 16 April 2020 (starts about 15.45). She had made a detailed study of the patient data from Wuhan. The figure of 0.1 was achieved by interrupting the transmission of the virus within households as well as between households. This was done by placing all persons confirmed to have Covid-19 or showing symptoms of Covid-19 (there was a lack of testing at the time) in field hospitals while all other traced contacts were placed in hotels rooms (common air conditioning disabled) or other special accommodation where cross-infection was less likely. Children went with parents. In China this approach was mandatory, but it is possible that it could be quite effective as a voluntary measure in the UK. The suppression of disease was rapid; the field hospitals were only open from the beginning of February to the 5th March.

The values for Italy and Germany are taken from an interview with Franco Locatelli, president of the health advisory council of Italy, in Corriere della Sera of 18th April.

At present we are closely following Italy in the numbers of cases. So we may also be looking at a 15 week descent from the peak to a manageable state unless we can do better than the Italians in our interruption of disease.