Prevelancd Incidence

Question 1

Explain why hospital admission for leptospirosis is not an appropriate calculation of incidence of the disease.

Answer 1

Why Hospital Admissions ≠ Incidence: Using hospital admissions to calculatethe incidence of Leptospirosis is inappropriate because:○ It only captures cases severe enough to require hospitalization.○ Mild or moderate cases treated in outpatient seings or not seeking medicalcare are missed.○ Asymptomatic infections are not captured.○ Access to healthcare and hospitalization practices can vary, aecting whogets admied.○ It represents only a fraction (oen the “tip of the iceberg”) of the total newcases occurring in the community.

Question 2

Explain why the incidence and prevalence for Leptospirosis are almost thesame for a year.

Answer 2

Incidence vs. Prevalence for Leptospirosis:○ The question notes incidence (315/100,000) and prevalence (332/100,000)were almost the same for a year. This occurs when the disease has a relatively short duration.○ Prevalence ≈ Incidence × Duration. If the average duration of illness (from onset to recovery or death) is short (e.g., a few weeks), the number of existing cases at any point (prevalence) will be close to the number of new cases occurring over a period (incidence). People either recover or die relatively quickly, so they don’t remain prevalent cases for long. The small difference(332 vs 315) represents the few cases existing from the previous year or those with slightly longer illness duration carrying over.

Question 3

Prevalence:

Answer 3

Measures the proportion of individuals in a population who havethe disease (new and existing cases) at a specic point in time (pointprevalence) or over a period (period prevalence). Reects the burden of thedisease in the population. Does not require follow-up. Numerator = all existingcases; Denominator = total population. Depends on both incidence andduration of the disease (Prevalence ≈ Incidence × Duration). Used forestimating population burden, planning health services.

Question 4

Incidence:

Answer 4

Measures the rate at which new cases of a disease occur in apopulation at risk during a specied period. It reects the risk of developingthe disease. Requires following a disease-free population over time.Numerator = new cases; Denominator = population at risk (or person-time atrisk). Less dependent on disease duration. Used for studying cause & eect,evaluating prevention measures. Types: Cumulative Incidence, IncidenceDensity/Rate.