Epidemiology module of practical skills for mbbs student

When the disease is occurring?

Compare the number of cases and deaths with previous weeks/ months/ years to see if there are any seasonal or cyclic trends. Table, bar or line diagrams are tools that enable analysis across time (temporal). These tools will help you to understand any increase or decrease in the incidence of a disease or the number of deaths for a particular reporting unit (as compared to other reporting units). Figure 10.1 shows yearly trend of measles cases and deaths in a tabular and graphic form.

The above data could be interpreted in the following manner. The increasing number of cases from 1999 onwards indicates a potential outbreak, improved reporting or a change in the detection and reporting protocols. The decreasing number of cases from 2002 onwards indicates improved control measures, under-reporting due to incomplete reports or change in the detection and reporting protocols. The plateau in the graph from 2006 onwards indicates either a stable situation or under reporting because of incomplete reports.