How the coronavirus spread undetected in the UK

How the virus spread undetected

By Feb. 23, when most British schools had ended their half-term holidays, Reuters estimates there were thousands of COVID-19 infections across the country. In areas such as Birmingham and nearby communities, there were already hundreds of infections, Reuters calculates*. Within a few weeks, the virus had taken hold and was rapidly spreading across the country.

How we estimated COVID-19 infections from deaths

For every COVID-19-related death, Reuters estimated there were at least 100 new infections on average three weeks prior*.

Deaths x 100 = Estimated infections

Estimated infections

Deaths

3 weeks prior

Weekly COVID-19 infections and deaths in the UK

Infections estimated by Reuters

COVID-19 deaths

Positive cases reported

A peak of 8,990

deaths reported

3 weeks prior

20k

0

Jan 26

Feb 23

Mar 22

Apr 19

May 17

Jun 14

A peak of 899,000

weekly infections estimated

800k

600k

400k

End of UK

half-term holiday

A peak of 30,231

cases reported

Lockdown begins

200k

0

Jan 26

Feb 23

Mar 22

Apr 19

May 17

Jun 14

PERCENTAGE OF ESTIMATED INFECTIONS confirmed as COVID-19 cases in England, Scotland and Wales

Infections were estimated based on deaths

but there were no reported positive cases

Less than 1% of estimated new infections

tested and confirmed as COVID-19 cases

1%-4% of estimated new infections

tested and confirmed as COVID-19 cases

COVID-19 positive cases were reported but there

were no deaths to estimate infections for that week

February 23

Glasgow

Manchester

Birmingham

London

Infections were estimated based on deaths

but there were no reported positive cases

Less than 1% of estimated new infections

tested and confirmed as COVID-19 cases

1%-4% of estimated new infections

tested and confirmed as COVID-19 cases

COVID-19 positive cases were reported but there

were no deaths to estimate infections for that week

March 8

Glasgow

Manchester

Birmingham

London

Infections were estimated based on deaths

but there were no reported positive cases

Less than 1% of estimated new infections

tested and confirmed as COVID-19 cases

1%-4% of estimated new infections

tested and confirmed as COVID-19 cases

COVID-19 positive cases were reported but there

were no deaths to estimate infections for that week

March 22

Glasgow

Manchester

Birmingham

London

How the virus spread undetected

By Feb. 23, when most British schools had ended their half-term holidays, Reuters estimates there were thousands of COVID-19 infections across the country. In areas such as Birmingham and nearby communities, there were already hundreds of infections, Reuters calculates*. Within a few weeks, the virus had taken hold and was rapidly spreading across the country.

How we estimated COVID-19 infections from deaths

For every COVID-19-related death, Reuters estimated there were at least 100 new infections on average

three weeks prior*.

Deaths x 100 = Estimated infections

Estimated infections

Deaths

3 weeks prior

Weekly COVID-19 infections and deaths in the UK

COVID-19 deaths

A peak of 8,990 deaths reported

3 weeks prior

20k

0

Jan 12

Jan 26

Feb 9

Feb 23

Mar 8

Mar 22

Apr 5

Apr 19

May 3

May 17

May 31

Jun 14

Positive cases reported

A peak of 899,000 weekly infections estimated

Infections estimated by Reuters

800k

600k

400k

A peak of 30,231 cases reported

200k

Lockdown begins

End of UK half-term holiday

0

Jan 12

Jan 26

Feb 9

Feb 23

Mar 8

Mar 22

Apr 5

Apr 19

May 3

May 17

May 31

Jun 14

PERCENTAGE OF ESTIMATED INFECTIONS confirmed as COVID-19 cases

in England, Scotland and Wales

Infections were estimated based on deaths but there were no reported positive cases

COVID-19 positive cases were reported but there were no deaths to estimate infections for that week

Less than 1% of estimated new infections tested and confirmed as COVID-19 cases

1%-4% of estimated new infections

tested and confirmed as COVID-19 cases

February 23

March 8

March 22

Glasgow

Manchester

Birmingham

London

*Methodology

To get a broad estimate of infections that went undetected, Reuters used mortality statistics. Researchers have found that, on average, COVID-19 kills 0.5% to 1% of people infected. So, using the upper limit to be conservative, Reuters backdated infections using official COVID-19 death counts for local areas.

The method is not exact. For example, not everyone dies exactly three weeks after infection. And the fatality rate will vary with the age distribution of people infected. But the estimate may also be an undercount because it does not take into account the large numbers of people whose death was likely linked to COVID-19 but this was not reflected on death certificates.

Note: Maps show local authorities for England and Wales, health board areas for Scotland. No local testing data available for Northern Ireland. Infection estimates until May 24, 2020.

Sources: Reuters analysis; Office of National Statistics; National Records of Scotland; Northern Ireland Statistics and Research Agency; Public Health England; Public Health Wales; Scottish government; Northern Ireland Department of Health

How the virus spread undetected

By Feb. 23, when most British schools had ended their half-term holidays, Reuters estimates there were thousands of COVID-19 infections across the country. In areas such as Birmingham and nearby communities, there were already hundreds of infections, Reuters calculates*. Within a few weeks, the virus had taken hold and was rapidly spreading across the country.

How we estimated COVID-19 infections from deaths

For every COVID-19-related death, Reuters estimated there were at least 100 new infections on average

three weeks prior*.

Deaths x 100 = Estimated infections

Estimated infections

Deaths

3 weeks prior

Weekly COVID-19 infections and deaths in the UK

COVID-19 deaths

A peak of 8,990 deaths reported

3 weeks prior

20k

0

Jan 12

Jan 26

Feb 9

Feb 23

Mar 8

Mar 22

Apr 5

Apr 19

May 3

May 17

May 31

Jun 14

Positive cases reported

A peak of 899,000 weekly infections estimated

Infections estimated by Reuters

800k

600k

400k

A peak of 30,231 cases reported

200k

Lockdown begins

End of UK half-term holiday

0

Jan 12

Jan 26

Feb 9

Feb 23

Mar 8

Mar 22

Apr 5

Apr 19

May 3

May 17

May 31

Jun 14

PERCENTAGE OF ESTIMATED INFECTIONS confirmed as COVID-19 cases

in England, Scotland and Wales

Infections were estimated based on deaths but there were no reported positive cases

COVID-19 positive cases were reported but there were no deaths to estimate infections for that week

Less than 1% of estimated new infections tested and confirmed as COVID-19 cases

1%-4% of estimated new infections

tested and confirmed as COVID-19 cases

February 23

March 8

March 22

Glasgow

Manchester

Birmingham

London

*Methodology

To get a broad estimate of infections that went undetected, Reuters used mortality statistics. Researchers have found that, on average, COVID-19 kills 0.5% to 1% of people infected. So, using the upper limit to be conservative, Reuters backdated infections using official COVID-19 death counts for local areas.

The method is not exact. For example, not everyone dies exactly three weeks after infection. And the fatality rate will vary with the age distribution of people infected. But the estimate may also be an undercount because it does not take into account the large numbers of people whose death was likely linked to COVID-19 but this was not reflected on death certificates.

Note: Maps show local authorities for England and Wales, health board areas for Scotland. No local testing data available for Northern Ireland.

Infection estimates until May 24, 2020.

Sources: Reuters analysis; Office of National Statistics; National Records of Scotland; Northern Ireland Statistics and Research Agency; Public Health England; Public Health Wales; Scottish government; Northern Ireland Department of Health

Deaths x 100 = Estimated infections

Estimated infections

Deaths

3 weeks prior

Weekly COVID-19 infections and deaths in the UK

COVID-19 deaths

Positive cases reported

Infections estimated by Reuters

A peak of 8,990

deaths reported

3 weeks prior

20k

0

Jan 26

Feb 23

Mar 22

Apr 19

May 17

Jun 14

A peak of 899,000 weekly infections estimated

800k

600k

400k

End of UK

half-term holiday

A peak of 30,231

cases reported

Lockdown begins

200k

0

Jan 26

Feb 23

Mar 22

Apr 19

May 17

Jun 14

PERCENTAGE OF ESTIMATED INFECTIONS confirmed as COVID-19 cases in England, Scotland and Wales

Infections were estimated based on deaths

but there were no reported positive cases

Less than 1% of estimated new infections

tested and confirmed as COVID-19 cases

1%-4% of estimated new infections

tested and confirmed as COVID-19 cases

COVID-19 positive cases were reported but there

were no deaths to estimate infections for that week

February 23

Glasgow

Manchester

Birmingham

London

Infections were estimated based on deaths

but there were no reported positive cases

Less than 1% of estimated new infections

tested and confirmed as COVID-19 cases

1%-4% of estimated new infections

tested and confirmed as COVID-19 cases

COVID-19 positive cases were reported but there

were no deaths to estimate infections for that week

March 8

Glasgow

Manchester

Birmingham

London

Infections were estimated based on deaths

but there were no reported positive cases

Less than 1% of estimated new infections

tested and confirmed as COVID-19 cases

1%-4% of estimated new infections

tested and confirmed as COVID-19 cases

COVID-19 positive cases were reported but there

were no deaths to estimate infections for that week

March 22

Glasgow

Manchester

Birmingham

London

*Methodology

To get a broad estimate of infections that went undetected, Reuters used mortality statistics. Researchers have found that, on average, COVID-19 kills 0.5% to 1% of people infected. So, using the upper limit to be conservative, Reuters backdated infections using official COVID-19 death counts for local areas. The method is not exact. For example, not everyone dies exactly three weeks after infection. And the fatality rate will vary with the age distribution of people infected. But the estimate may also be an undercount because it does not take into account the large numbers of people whose death was likely linked to COVID-19 but this was not reflected on death certificates.