the average number of secondary infected individuals generated from one primary infected individual in a population where all individuals are equally susceptible to a disease. In a basic model of social distancing, where a proportion of the population engages in social distancing to decrease their interpersonal contacts to a fraction of their normal contacts, the new effective reproduction number is given by: Where the value of can be brought below1 for sufficiently long, containment is achieved, and the number infected should decrease. For any given period of time, the growth in the number of infections can be modeled as: where: is the number of infected individuals after incubation periods (5 days, in the case of COVID-19) Using COVID-19 as an example, the following table shows the infection spread given: A: No social distance mitigation B: 50% reduction in social interaction C: 75% reduction in social interaction Effectiveness An empirical study published in July 2020 in The BMJ (British Medical Journal) analyzed data from 149 countries, and reported an average of 13% reduction in COVID-19 incidence after the implementation of social distancing policies. Another study found that four social distancing interventions combined resulted in a reduction of the infection rate from 66% to less than 1%. See also COVID-19 party Civil inattention Herd immunity Lockdown Pest house Stay-at-home order References External links CDC Social Distancing American Red Cross: How to Social Distance Johns Hopkins: Social and Physical Distancing Infectious diseases Quarantine Epidemics Epidemiology Medical hygiene