Reproduction number (R0)
\riprəˈdʌkʃən\ \nʌmbər\
The reproduction number (R0, generally pronounced “R naught”) of a transmissible disease is the number of people to whom one carrier will transmit the disease during their infectious period.
If R0 is greater than 1, then the number of people with the disease will increase, if it is smaller than 1 then the disease will contract and eventually die out.
R0 depends on how contagious the disease is and how many people come into contact with each infected person. Vaccination can be used to reduce how many people will contract a disease; quarantine, isolation and social distancing policies can all be used to reduce the number of people exposed to potential infection. All of these suppression and mitigation policies have the goal of reducing R0.