The public health people know that the diagnosis of SF is very hit and miss now - this is from last week's HPA epidemiological update:
"Interpretation of data to produce estimates on the number of new cases continues to be subject to a considerable amount of uncertainty with the move to the National Pandemic Flu Service (NPFS). HPA modelling gives an estimate of 53,000 (range 27,000 – 115,000) new cases in England in week 42. The estimated number of new cases has increased in all regions and age groups."
And this:
"The number of pandemic influenza (H1N1) 2009 cases is estimated using a statistical model. The model
relies on data from various surveillance systems and studies. The key surveillance systems that are used
consist of the primary care based Q Surveillance® scheme, the RCGP and HPA Regional Microbiology
Network sentinel surveillance scheme and latterly data from the NPFS. To provide an estimate of the number
of pandemic cases that present to their GP the estimated number of primary care attendances with influenza
like illness is multiplied by the positivity rates from testing within sentinel GP schemes. To estimate the
number of pandemic (H1N1) 2009 that present to NPFS, the number of NPFS antiviral collections are
multiplied by positivity rates from testing from people contacting NPFS. To provide an overall estimate of
number of cases in the population, these two estimates are combined and scaled up to allow for a range of
30% to 70% of pandemic (H1N1) 2009 cases contacting either NPFS or a GP."
(NPFS is the pandemic hotline/website). I assume that means that if they end up estimating that the H1N1 positivity rate from testing of people contacting NPFS was 10%, then they would divide the total number of Tamiflu prescriptions from the hotline by 10 to get a guess at the number of real H1N1 cases. Then they combine that with estimates based on extrapolating from the 'sentinel' GP practices that have always report their consultation rates and sent samples off for testing, all year round, for tracking seasonal flu.
I suppose eventually as they get more data they might tweak the criteria for Tamiflu so it can be targeted more accurately at real H1N1 cases.
It's going to be a bad winter to get more than one respiratory bug with a temperature .