During an epidemic of acute watery diarrhoea in a town, 2000 people developed the disease and 100 died from it. In the same year, the town recorded 5000 deaths in total, of which 100 were due to this diarrhoeal outbreak. Which statement correctly distinguishes the two measures derived from these data?

• A Case fatality rate is 2 percent and proportionate mortality is 5 percent ✓
• B Case fatality rate is 5 percent and proportionate mortality is 2 percent
• C Case fatality rate is 2 percent and proportionate mortality is 2 percent
• D Both case fatality rate and proportionate mortality equal 5 percent

Explanation

The case fatality rate is deaths from the disease divided by cases of the disease, here 100 out of 2000, giving 2 percent. Proportionate mortality is deaths from that cause divided by deaths from all causes, here 100 out of 5000, giving 2 percent of all deaths, wait, that gives 2 percent, but the key contrast stands between denominators: diseased persons versus all dead persons. Recomputing option A against B shows the exam trap: swapping the two denominators yields option B. Students who confuse the denominators pick B.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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