Epidemiological Parasite Rate (PR) Calculator
Calculate endemicity levels based on age-specific surveys.
Analysis Results
Calculated Parasite Rate (PR): 0%
Age Group Filter:
Understanding the Parasite Rate (PR)
The Parasite Rate (PR) is a fundamental metric in epidemiology, particularly in malaria research. It represents the proportion of a specific population that is found to be carrying parasites in their peripheral blood at a given point in time.
Which Age Group is the Standard?
While parasite rates can be calculated for any demographic, the 2 to 10-year-old age group (often denoted as PfPR2-10 for Plasmodium falciparum) is the globally recognized standard. This specific group is used because:
- Stable Immunity: Children in this range have lost maternal immunity but have not yet developed the high levels of clinical immunity found in adults.
- Reflective Data: This group provides the most sensitive and stable indication of transmission intensity in a community.
- Comparability: Using a standardized age range allows researchers to compare endemicity levels between different regions and over different time periods.
Endemicity Classifications
Based on the Parasite Rate in the 2-10 year age group, the World Health Organization (WHO) traditionally classifies regions into four levels of endemicity:
| Classification | Parasite Rate (PR) Range | Description |
|---|---|---|
| Hypoendemic | 0% – 10% | Low transmission; limited community impact. |
| Mesoendemic | 11% – 50% | Moderate transmission; common in rural tropical areas. |
| Hyperendemic | 51% – 75% | High transmission; intense seasonal or year-round activity. |
| Holoendemic | Over 75% | Extremely high transmission; nearly everyone is infected. |
How to Use the Calculator
To use this tool, input the total number of individuals tested within your chosen age group and the number of those individuals who tested positive for the parasite (via microscopy or RDT). The calculator will automatically determine the percentage and the endemicity classification based on standard epidemiological thresholds.
Example Calculation
If a survey of 500 children aged 2-10 years in a sub-Saharan village finds that 125 children have detectable parasites in their blood:
Formula: (Positive Cases / Total Sample) × 100 = PR
Calculation: (125 / 500) × 100 = 25%
In this scenario, the region would be classified as Mesoendemic.