Prevalence

Disease prevalence maps highlight the proportion of people within a population that have a specific disease (both existing and emerging cases), prevalence can be measured at a specific point in time (point prevalence) or over a specific time period (period prevalence). Prevalence maps indicate how widespread a disease is.

Strategic or operational?

Both

Basemap, baseline or situational?

Baseline and Situational

When might it be produced?

Prevalence maps are used to understand how widespread a disease is. They can be created at the beginning of an emergency to understand the underlying disease profile of a population pre-emergency as well as during an emergency to understand how widespread a disease has become.

Intended audience

Invariably health is linked to many other vulnerabilities and is impacted by all eleven clusters in the UN system (sectors of the humanitarian system that help to coordinate a humanitarian response), in particular:

  • Nutrition

  • Water, Sanitation and Hygiene (WASH)

  • Logistics - transport / access

The intended audience includes a variety of actors either directly involved in health, or those supporting health needs:

  • Ministry of Health / Department for Health

  • National Health Care Providers

  • Local Government

  • Civil Society / Community Organisations

  • Affected communities / population

  • National and International health related NGOs

  • National Red Cross / International Federation of Red Cross

  • World Health Organisation

  • Emergency Medical Teams /Emergency Medical Teams Coordination Cell

Influence on humanitarian decisions

Will be dependent on if the maps are strategic, operational or both and will vary by intended audience. To be updated based on planned expert interviews.

Access to timely and accurate data is essential for a health response. It is important to get the best available data although it may not always be perfect. Questions should be asked such as:

When was the data collected? What time period does it cover? When will it next be updated? How accurate is the data? Are the figures actual or estimates? Is it point prevalence or period prevalence? What population was used as the denominator? Is the rate per 1,000, 10,000 or 100,000 population?

Prevalence is calculated as the volume of a population with a specific disease divided by the population, if population data is not available it may also be shown as a volume of people that have a specific disease at a point in time or over a given time period.

Robust information management and governance is essential when accessing, storing and visualising health data. The agreed use of the data must be established and recorded from the outset.

A process of data manipulation may be required to ensure individuals, families or villages can not be identified. A number of methods can be used to achieve this including the suppression of small numbers, aggregation of data to a higher level and minimising the use of other data / detail on a map that could make identification easier. These checks must be in place to ensure patient’s right to privacy and dignity are maintained.

Data

  • Count of cases at a specific point in time

  • Count of cases over a given time period

  • Count of cases at a specific point in time divided by population at risk at the same point in time - often shown as rate per 1,000, 10,000 or 100,000 population

  • Count of cases over a given time period divided by either the average population over the time period or a midpoint population - often shown as rate per 1,000, 10,000 or 100,000 population

Resources

  • Global Health Cluster

  • World Health Organisation

  • Emergency Medical Teams

  • Health Resource Availability Monitoring System (HeRAMS)

  • Early Warning, Alert and Response System (EWARS)

  • The Sphere Handbook - Minimum standards in Health action

  • Multi-Cluster / Sector Initial Rapid Needs Assessment (MIRA)

  • The International Federation of Red Cross and Red Crescent Societies

  • Ministry of Health / Department of Health (country specific)

  • ACAPS

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