How contagious is a disease?

How contagious is a disease?

The reproduction number, or R0, describes how many additional cases of a disease each infected person will cause during their infectious period. 

Source: J. Eisenberg, R0: How Scientists Quantify the Intensity of an Outbreak Like  Coronavirus and Its Pandemic Potential

Basic protective measures against the COVID-19: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public

Guide to prevent the spread if you are a confirmed or suspected patient of COVID-19: https://www.cdc.gov/coronavirus/2019-ncov/hcp/guidance-prevent-spread.html