Period prevalence is the number of individuals identified as cases during a specified period of time, divided by the total number of people in that population.

**Formula to calculate period prevalence.**

**Example:**

Suppose in the month of July the Covid-19 cases were 600 in Nairobi County, if the Nairobi’s population in July was 2 million, calculate the period prevalence.

Thus, the period prevalence is 0.03%.