The paper is both well written and well organised. The paper demonstrated that the prospective space-time scan statistic can be used to track both the state/progress of existing clusters but also find emerging clusters at a county level.

The effectiveness of the method can be seen by comparing tables 1 and 2 where the clusters from 22nd of Jan 2020 to the 9th of March 2020 was being compared with the clusters detected from 22nd Jan 202 to 27th March 2020. The evolution of the existing clusters and new emerging clusters can be detected. One of the important aspects of the algorithm is that as new data i.e. cases are added, the same analysis can be systematically carried out on the new set of data also with the existing data.

The paper is significant in that it shows an effective method to track infectious disease. The same kind of analysis might also be used to find the epicentre of infectious disease and could also be applied on a global scale provided the same level of information is available. This could also as a preventative measure by informing people living in areas where new clusters are emerging about precautions that could be taken and thus stop the propagation of the infection.