Infection rates fell through August and the first part of September but have been rising for
the past although they remain within the normal winter baseline. As anticipated,
rates are rising mainly in the 5-15 age group and figures suggest the early stages of a
second wave of A/H1N1sw (swine lineage). There were 9000 total cases in England last
week and 5200 the week before. There have been 70 fatalities since the outbreak began.
The vast majority of circulating flu in the UK is swine flu strain, and there have been just two
antiviral resistant cases in the UK.
This update provides the latest advice on influenza type A/H1N1sw, referred to as H1N1.
Advice includes:
New UK planning assumptions (Section 2)
Vaccination programme (Section 3)
General advice on H1N1 (Section 4)
Antiviral medication (Section 5)
Advice for workplaces (Section 6)
New UK Planning Assumptions
These were published at the beginning of September by the DoH and contain projections for
the 'reasonable worst case scenario'.
Planning assumptions to mid-May 2010
Clinical attack rate: up to 30% of the population
Peak clinical attack rate: 4.5 to 8% of population per week
Case complication ratio: up to 15% of clinical cases
Case hospitalization ratio:
up to 1% of clinical cases, of whom up to 25% could require
intensive care treatment
Case fatality ratio: up to 0.1% of clinical cases
Peak absence rate: up to 12% of the workforce
Roodlane Medical Limited
Tuesday 29 September 2009
2
It is anticipated that 30% of the population will be infected with A/H1N1sw in total (over the
course of the current outbreak) with as many as 5% of the population being affected at any
one time. For closed environments like schools and offices, this figure could be higher with
an estimate of up to 12% of workforces being affected at any one time. The figures have
been significantly revised downwards from initial assumptions.
Case fatality rates of up to 1:1000 are similar to seasonal flu although we know that younger
children are at increased risk of severe illness from this virus compared to seasonal flu.
Pregnant women are at increased risk from seasonal and H1N1 flu and the risk from H1N1
per se
is not greater on a case by case basis.
Vaccination Programme
The European medicines agency (EMEA) has authorized the Glaxo SmithKline vaccine
Pandemrix© and given a positive opinion on a second vaccine called Focetria© produced by
Novartis. This is expected to get full authorisation within days. A third vaccine, Celvapan©,
produced by the drug company Baxter is still under review, although stockpiles of vaccine
have been available in the UK for over a month now.