If 39 meningitis cases are reported in a population of 780,000, what is the incidence rate per 100,000 population?

If 39 meningitis cases are reported in a population of 780,000, what is the incidence rate per 100,000 population?

• A. 5/100,000
• B. 0.5/100,000
• C. 50/100,000
• D. 0.5/1,000

Answer: (A)

Incidence rate per 100,000 shows how many new cases occur in a population standardized to 100,000 people. Calculate by (new cases / population) × 100,000. Here: (39 / 780,000) × 100,000 = 0.00005 × 100,000 = 5. So there are 5 new meningitis cases per 100,000 people. This standardization helps compare disease occurrence across populations of different sizes. The other numbers don’t fit because they correspond to different counts: 0.5 per 100,000 would require about 3.9 cases; 50 per 100,000 would require about 390 cases; 0.5 per 1,000 equals 50 per 100,000, which also doesn’t match the given 39 cases.

Incidence rate per 100,000 shows how many new cases occur in a population standardized to 100,000 people. Calculate by (new cases / population) × 100,000.

Here: (39 / 780,000) × 100,000 = 0.00005 × 100,000 = 5. So there are 5 new meningitis cases per 100,000 people.

This standardization helps compare disease occurrence across populations of different sizes. The other numbers don’t fit because they correspond to different counts: 0.5 per 100,000 would require about 3.9 cases; 50 per 100,000 would require about 390 cases; 0.5 per 1,000 equals 50 per 100,000, which also doesn’t match the given 39 cases.