Public Health Evidence Bulletin

17th July 2020, no. 295

Characteristics of people testing positive for Covid-19

National picture
The Office for National Statistics release results from the Covid-19 Infection Survey weekly. This survey samples individuals from private residential households and invites them to test for infection using home testing swab kits. A report on Covid-19 infections in the community that utilises results from the Covid-19 Infection Survey has recently been released. It looks at potential risk factors (age, sex and ethnicity) for those testing positive for SARS-CoV-2, with or without symptoms, between 26th April and 27 June 2020. The following key messages emerged:

  • There was no evidence of differences in estimated infection rates among males and females, or different age groups over the study period.
  • Infection rates were lower for home workers than for those working outside of the home.
  • Infection rates were higher among patient- and resident-facing health and social care roles than other occupations.
  • There was some evidence to suggest that infection rates are lower for those living in households of fewer people.
  • Infection rates are higher for those reporting evidence of symptoms of COVID-19.
  • Only around one-third of individuals testing positive for COVID-19 on a swab test reported having symptoms.
  • Individuals coming into recent contact with people suspected of having COVID-19 are much more likely to test positive for COVID-19 than those with no contact with suspected cases.
  • The estimated number of people testing positive in the survey with an ethnic group other than White were too small to draw conclusions on ethnic variation.

Prevalence of suspected Covid-19 infections in primary care by ethnic group 
A recent study of over 1.3 million people registered with 157 practices across  City and Hackney, Waltham Forest, Newham and Tower Hamlets CCGs examined characteristics of those with and without suspected COVID-19 codes from the first January to the end of April 2020. After accounting for age, sex, deprivation quintile, BMI and count of long-term conditions, the study found that patients from South Asian and Black ethnic groups were at a significantly higher risk of a suspected COVID-19 diagnosis in primary care. These results add to the findings from the national survey (above).

Local testing data
As at 11th July,  808 Covid-19 cases were confirmed in Hackney, and 18 in the City of London. Of 12,994 tests so far done, 83% of confirmed cases were done under Pillar 1 and 17% were done under Pillar 2. Between March and late April, the majority of cases in City and Hackney were identified through Pillar 1. More recently the majority of cases have been detected through Pillar 2 testing.

Age, sex, and postcode data were available for 825 of the 826 total positive cases in City and Hackney. Local analyses suggest no difference between the crude rate of positive cases per 100,000 population among males and females. Whilst there was a similar count of tests among the age groups 20 to 49, 50 to 69 and 70 and over, the crude rate of positive cases per 100,000 population among these age groups differed significantly with the highest rates among the residents aged 70 and over (Figure 1). 

Fig 1 Number and crude rate of COVID-19 cases in City and Hackney by age, 6th March to 11th July 2020

Data source: Public Health England daily cases, Greater London Authority 2018 housing-led population projections 2020

No significant differences in the crude rate of positive cases per 100,000 population by area deprivation quintile, which can be determined using the postcode, were observed. No other socio-demographic data are available for the cases at present.

The Department of Health and Social Care define testing methods as follows:
Pillar 1: swab testing in Public Health England labs and NHS hospitals for those with a clinical need, and health and care workers
Pillar 2: swab testing for the wider population which includes tests carried out at care homes, mobile testing units and home swab testing kits delivered by post.
Copyright © 2020 City & Hackney Public Health Team, All rights reserved.

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