Case-fatality rate

Statistical measure of the severity of a disease

Template:Medical statistics

The case-fatality rate (CFR) is a measure used in epidemiology to assess the severity of a disease by calculating the proportion of individuals diagnosed with a particular disease who die from that disease within a specified period. It is expressed as a percentage and is a crucial metric in understanding the impact of infectious diseases, especially during outbreaks.

Definition

The case-fatality rate is defined as:

\[ \text{CFR} = \left( \frac{\text{Number of deaths from a disease}}{\text{Number of diagnosed cases of the disease}} \right) \times 100 \]

This formula provides the percentage of cases that result in death, offering insight into the lethality of the disease.

Calculation

To calculate the CFR, accurate data on both the number of deaths and the number of diagnosed cases is required. The time frame for these measurements should be consistent to ensure the reliability of the CFR.

Factors Affecting CFR

Several factors can influence the case-fatality rate, including:

• Age and Health of the Population: Older populations or those with pre-existing health conditions may have higher CFRs.
• Quality of Healthcare: Access to and quality of medical care can significantly affect outcomes.
• Virulence of the Pathogen: More virulent strains of a pathogen can lead to higher CFRs.
• Timeliness of Diagnosis and Treatment: Early detection and treatment can reduce the CFR.

Applications

The CFR is used by public health officials to:

• Assess the severity of an outbreak.
• Allocate resources effectively.
• Inform public health policies and interventions.

Limitations

While the CFR is a useful measure, it has limitations:

• Underreporting: Not all cases or deaths may be reported, leading to inaccurate CFRs.
• Time Lag: The CFR can change over time as more data becomes available.
• Differences in Case Definitions: Variations in how cases are defined can affect the CFR.

Examples

During the COVID-19 pandemic, the CFR was a critical metric for understanding the impact of the virus. However, it varied widely between countries and over time due to differences in testing, healthcare systems, and population demographics.

Also see

• Mortality rate
• Infectious disease
• Epidemiology
• Pandemic
• Public health