Covid Scotland: Only 30 per cent of patients ill with virus

However, it also stressed that all Covid admissions, regardless of diagnosis, still "contribute significantly to hospital pressures".

The report highlighted the extent of asymptomatic infections, which have become more common during the Omicron wave.

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It found that between December 2021 and mid-May 2022, 66 per cent of all Covid patients who had probably or definitely been infected while in hospital had no virus symptoms at the point of their positive test.

Mortality patterns due to the virus have also shifted significantly.

From January to the end of April this year, 29% of "Covid deaths" - where a person dies within 28 days of a positive test - were unrelated to the infection.

That compares to just 1% of Covid deaths during the first wave, from March to June 2020.

(Source: Public Health Scotland)

The effect is most pronounced among those aged 19 and under, where 75% of "Covid deaths" were directly caused by the virus during wave one compared to just 9.1% in the Omicron wave.

On hospital admissions, the report pointed to data gathered by NHS Grampian which shows that the proportion of Covid patients who were definitely or probably admitted to hospital "because of" the infection has declined steadily from an average of 68% between June and December 2021, to 30% by April of this year - of whom just 20% were "definitely" due to Covid.

(Source: Public Health Scotland)

In Grampian, between January and April, 71% of the Covid bed occupancy was made up of patients with incidental infections who were in hospital for other reasons.

This is echoed in national data compiled by PHS.

To date, Covid hospital admissions have included anyone who has been admitted to hospital with a positive Covid test if they tested positive 14 days before their admission, upon their admission or during their admission, irrespective of their symptoms and whether or not they were admitted because of Covid.

Separate information on "reason for admission" is recorded in patients' discharge diagnosis on the Scottish Morbidity Record 01 (SMR01), but there is a three-month lag in this data becoming available.

PHS examined trends in Covid admissions based on what percentage were emergency admissions with community-acquired Covid, as a "reasonable indicator" for the impact of the disease on NHS demand.

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It found that in early November 2021, 78% of all Covid admissions were emergency admissions with community-acquired Covid.

By the week ending May 1, this had fallen to 59%.

However, PHS said this was liable to be an overestimate since, from January 2022, only half of these types of admissions actually had Covid listed as a primary diagnosis on discharge, compared to 70-80% in November and December of 2021.

NB: Rapid = data on admission; SMR01 = data on discharge (Source: Public Health Scotland)

This is "repeated across all age-groups" and would suggest that just under 30% of Covid admissions nationally are actually being caused by the disease.

The most recent update for Scotland notes that there were 1,298 Covid positive patients in hospital as of June 26 - suggesting that around 389 will have Covid as their primary diagnosis.

Nonetheless, the virus complicates care delivery due to high numbers of infected staff absent and requirements to cohort Covid and non-Covid patients in separate wards, with knock-on bed losses.

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PHS states: "It should be noted that regardless of admission reason, all admissions with recent COVID-19 diagnosis contribute significantly to hospital pressures in association with the required infection prevention and control measures.

"These patients still require isolation from other patients for infection control purposes and have other resource implications on critical care units and the wider hospital."