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Influenza change in the admission rate of critical patients compared with previous 7 days

Last updated on Monday, 1 July 2024 at 10:26am

Summary

Topic
Influenza
Category
headline
API name
influenza_headline_ICUHDUadmissionRatePercentChange

Rationale

Seasonal influenza occurs every year and is a key driver for winter pressure on the NHS. The impact of influenza on the NHS depends on several factors: which strains of the virus are circulating and who is most likely to be affected, how effective the annual vaccine is, how many people are immunised, and winter temperatures. Understanding rates and patterns of hospital admissions can help to inform planning around hospital pressures including beds and staffing.

Definition

This metric shows the percentage change in the rate per 100,000 people of the total number of people with confirmed influenza admitted to a hospital Intensive Care Unit (ICU) or High Dependency Unit (HDU) in the last 7 days compared to the previous 7 days.

Methodology

Updates from SARI Watch are published in the UKHSA National Influenza and COVID-19 Surveillance Report on a Friday (weekly during influenza season and fortnightly in the summer months), and contains data up to the previous Sunday. This metric shows the percentage change in rate per 100,000 people in the NHS trust catchment population who were admitted to ICU or HDU with laboratory-confirmed influenza in the last 7 days. It is calculated by subtracting the rate per 100,000 people in the 7 days prior to the last 7 days from the rate people 100,000 people in the last 7 days, then dividing by the rate per 100,000 people in the 7 days prior to the last 7 days. The rate is calculated by counting the number of influenza-related admissions to ICU or HDU in the 7 day period, dividing by the catchment population of the NHS trust and then multiplying by 100,000.

Caveats

Hospital provider trusts do not have geographically defined boundaries for their client population nor do they have all encompassing lists of registered patients. OHID has adopted a proportionate flow method to calculate catchment populations. Using this method, Hospital Episode Statistics (HES APC) data was used to count the number of patients admitted to hospital from every small geographical area in England (based on middle super output area (MSOSA), which are standard geographies of 7,200 people). For each MSOA, the number of patients admitted to each hospital trust was calculated as a proportion of all patients from that MSOA admitted to hospital. this proportion was then applied to the resident population of each MSOA and the resulting population counts added to give an overall hospital catchment population. The catchment year applies to the year of mid-year population estimates used to calculate the population.

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