Irrespective of the fact that 50,000 of 5,000,000 is 1% rather than 0.1%, here's a v short selection of data that might help to clarify some of the differences between flu and COVID-19.
12% increase in people getting tested which is good (now 1.74m in a week(!)), but note from 6th Nov, pillar 2 now includes people having the rapid lateral flow tests (e.g. Liverpool pilot) and this will only increase in numbers.
The knock-on impact is lower P2 positivity rates.
The implications of this is that it makes it far harder to interpret positivity rates, esp if you don't separate out test device, or asymptomatic vs symptomatic testing.
Latest PHE flu & COVID surveillance report, up to 15th Nov.
- ⬆️Case rates in over 70yrs.
- ⬆️hospitalisations, ICU admissions & deaths.
- Big variation by region, ethnicity, age, and deprivation.
- (+ some good news on flu & flu jabs)
Confirmed cases of COVID plateaued this week, and positivity rates dropping.
Still probably a little early to see results of 6th Nov restrictions, but local restrictions likely important. And new use of lateral flow tests (pillar 2) may be contributing to lower positivity rates.
And case rates falling across most aged but crucially NOT among age 70yrs+
Lots happened during this week
- schools back after half term
- Liverpool's mass testing started on 6th Nov
- national restrictions (second lockdown-ish) started 5th Nov
Number of cases continued to rise, but overall positivity dipped for the first time suggesting more testing now being done.
As mass testing starts, gets increasingly important to separate asymptomatic from symptomatic testing.
One thing missing is positive predictive and negative predictive values (PPV and NPV) that crucially depend on what proportion of people being tested have disease - the prevalence.
Take recent ONS survey - 1.1% of pop infected: PPV is 73%, meaning around 1 in 4 positive tests are false positives
(NPV is 99.7% - if you test -ve, you are)
Test 1000 people: there will be 8 true positives, 3 false positives, 3 false negatives, and 986 true negatives.
If in NW where prevalence is 2.2%, PPV rises to 84% (about 1 in 6 positive tests are false)
BUT in SE, prevalence is 0.5% meaning PPV is 55%, i.e. every other positive result is a false positive.