Measurements of prevalence do have their limitations though, not least because they are influenced by many other factors of the disease. To account for this, an estimate of incidence is derived which uses the assumption (from the University of Southampton) that there are 1.3 individuals infected for every laboratory confirmed case. Many terms that were unknown to the average person before 2020 have, through the COVID-19 pandemic, become commonplace. We have used the analogy of water entering and leaving a bathtub to try and explain these terms and their limitations. Decisions made during this pandemic have relied on both the incidence and estimated prevalence of the disease and will continue to be used to inform the provision of appropriate public health advice and support measures such as either relaxing or strengthening local restrictions. Public Health Agency With that in mind, there’s still a lot of terminology used daily in news reports and online articles that are difficult to understand. It is more often used for chronic diseases, such as diabetes, because of the challenges of monitoring recovery and deaths for infectious diseases. Sarah Arnold, Senior Surveillance and Information Scientist in Health Protection, Dr Lynsey Patterson, Head of Health Protection Surveillance, and Dr Claire Neill, Specialty Registrar, Public Health Agency. Turning to COVID-19, the prevalence of COVID-19 in Northern Ireland is the total number of active cases in the country at a specific time. resources such as facilities and personnel. The design and planning of outcome focused children’s services. For this reason, both measures are necessary to give a better understanding of the disease. Often these words are used interchangeably however, when it comes to surveillance and epidemiological analyses these words have both distinct meanings and purpose. As with the prevalence, to facilitate comparisons we express this number as a rate per 100,000 population (an incidence proportion). To opt-out click for more information. We have used the analogy of water entering and leaving a bathtub to try and explain these terms and their limitations. BT2 8BS, ©2020 Public Health Agency The most recent estimate of the incidence rate is 20.3 per 100,000 population. Let’s take the term prevalence first and define it in the context of disease. Analogy of prevalence and incidence: The water flowing down the waterfall symbolizes incidence and water collecting in the pool at the base symbolizes prevalence. The former is commonly used in surveillance as we often don’t have access to detailed individual level data that would be available, for example, in a specialised cohort study. Prevalence and incidence are two highly important measures of disease used in epidemiology. Prevalence and incidence are two highly important measures of disease used in epidemiology. To help understand the difference between incidence and prevalence, epidemiologists often refer to the familiar concept of water entering and leaving a bath. If the incidence is high, the water will be gushing into the bathtub whereas if it’s low, water may enter the bathtub a drip at a time. The Relationship Between Incidence and Prevalence - YouTube In the latest weekly report, as of 16 August 2020, the prevalence of active cases is estimated to be 31 per 100,000 population assuming 50% of cases have no symptoms. that occur in a group during a certain time, – Time = the period during which the cases, – the effects of exposure to a hypothesized, are under observation for different lengths, Number of new cases during the time period. Notable examples of this include incidence and prevalence. 12-22 Linenhall Street Linenhall Street Unit Belfast The prevalence is an extremely useful measure in public health, particularly for service planning, as it allows us to understand the burden on the health and social care system at a particular point in time. This is where the incidence can be extremely useful. If we refer to our bathtub, the prevalence is the amount of water in the bathtub at a specified point in time. Therefore, the prevalence of a disease in a population is influenced by a number of parameters: the number of new cases (turning on the tap), the speed of recovery – which is influenced by disease severity and treatment options (evaporation) and the number of people that lose their lives to the disease (releasing the plug). Therefore, the prevalence of COVID-19 in Northern Ireland is estimated using different assumption about the proportion of the population reporting symptoms. As we all know, this quantity is not static and we can easily add more water, by turning on the tap, as well as lose water through evaporation or by opening the plug. 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