Early spread of the 2009 influenza A(H1N1) pandemic in the United Kingdom--use of local syndromic data, May-August 2009.

Abstract

Following the confirmation of the first two cases of pandemic influenza on 27 April 2009 in the United Kingdom (UK), syndromic surveillance data from the Health Protection Agency (HPA)/QSurveillance and HPA/NHS Direct systems were used to monitor the possible spread of pandemic influenza at local level during the first phase of the outbreak. During the early weeks, syndromic indicators sensitive to influenza activity monitored through the two schemes remained low and the majority of cases were travel-related. The first evidence of community spread was seen in the West Midlands region following a school-based outbreak in central Birmingham. During the first phase several Primary Care Trusts had periods of exceptional influenza activity two to three weeks ahead of the rest of the region. Community transmission in London began slightly later than in the West Midlands but the rates of influenza-like illness recorded by general practitioners (GPs) were ultimately higher. Influenza activity in the West Midlands and London regions peaked a week before the remainder of the UK. Data from the HPA/NHS Direct and HPA/QSurveillance systems were mapped at local level and used alongside laboratory data and local intelligence to assist in the identification of hotspots, to direct limited public health resources and to monitor the progression of the outbreak. This work has demonstrated the utility of local syndromic surveillance data in the detection of increased transmission and in the epidemiological investigation of the pandemic and has prompted future spatio-temporal work.

Full text

Page 1

1www.eurosurveillance.org
Surveillance and outbreak reports
Early spread of the 2009 infuenza A(H1N1) pandemic
in the United Kingdom – use of local syndromic data,
May–August 2009
S Smith (sue.smith@hpa.org.uk)1, G E Smith1, B Olowokure2, S Ibbotson1, D Foord3, H Maguire4, R Pebody5, A Charlett4,
J Hippisley-Cox6, A J Elliot1
1. Real-time Syndromic Surveillance Team, Health Protection Agency, Birmingham, United Kingdom
2. West Midlands Regional Epidemiology Unit, Health Protection Agency, Birmingham, United Kingdom
3. NHS Direct, Linford Wood East, Milton Keynes, United Kingdom
4. Health Protection Agency London, Regional Epidemiology Unit, London, United Kingdom
5. Health Protection Agency, Centre for Infections, London, United Kingdom
6. Division of Primary Care, School of Community Health Sciences, University of Nottingham, Nottingham, United Kingdom
Citation style for this article:
Smith S, Smith GE, Olowokure B, Ibbotson S, Foord D, Maguire H, Pebody R, Charlett A, Hippisley-Cox J, Elliot AJ. Early spread of the 2009 infuenza A(H1N1)
pandemic in the United Kingdom – use of local syndromic data, May–August 2009. Euro Surveill. 2011;16(3):pii=19771. Available online: http://www.
eurosurveillance.org/ViewArticle.aspx?ArticleId=19771
Article published on 20 January 2011
Following the confirmation of the first two cases of
pandemic influenza on 27 April 2009 in the United
Kingdom (UK), syndromic surveillance data from the
Health Protection Agency (HPA)/QSurveillance and
HPA/NHS Direct systems were used to monitor the
possible spread of pandemic influenza at local level
during the first phase of the outbreak. During the early
weeks, syndromic indicators sensitive to influenza
activity monitored through the two schemes remained
low and the majority of cases were travel-related. The
first evidence of community spread was seen in the
West Midlands region following a school-based out-
break in central Birmingham. During the first phase
several Primary Care Trusts had periods of exceptional
influenza activity two to three weeks ahead of the
rest of the region. Community transmission in London
began slightly later than in the West Midlands but
the rates of influenza-like illness recorded by general
practitioners (GPs) were ultimately higher. Influenza
activity in the West Midlands and London regions
peaked a week before the remainder of the UK. Data
from the HPA/NHS Direct and HPA/QSurveillance sys-
tems were mapped at local level and used alongside
laboratory data and local intelligence to assist in the
identification of hotspots, to direct limited public
health resources and to monitor the progression of
the outbreak. This work has demonstrated the utility
of local syndromic surveillance data in the detection
of increased transmission and in the epidemiologi-
cal investigation of the pandemic and has prompted
future spatio-temporal work.
Introduction
The first two cases of pandemic influenza in the United
Kingdom (UK) were confirmed in Scotland on 27 April
2009 [1]. Initially UK policy was to contain the spread
of the virus and during the early stages the main focus
of surveillance was on virologically confirmed cases.
This containment policy continued until 2 July when the
Government announced that due to further spread of
the disease the UK was moving to a treatment (mitiga-
tion) phase [2]. A key factor in this decision was the
presence of sustained community transmission. Data
from a range of national surveillance systems, includ-
ing syndromic surveillance data, were used during the
pandemic to assess when the change from sporadic
cases to more widespread community transmission
occurred.
Syndromic surveillance systems monitor generic symp-
toms and/or clinically diagnosed disease in order to
provide timely information at an earlier stage of illness
(compared to laboratory-confirmed diagnosis) [3]. Data
are captured electronically, often using information col-
lected for other purposes, to create large datasets that
can be analysed rapidly, some systems being able to
provide daily data. Some systems are well established,
for example the Royal College of General Practitioners
Weekly Returns Service has many years of historical
data that can be used to monitor longer-term disease
trends [4,5]. Syndromic surveillance can provide early
warning of, for example, seasonal rises in influenza
and norovirus infections and can trigger appropriate
public health action but can also be used to alert to
unexpected events such as an unusual rise in illness
that could indicate an outbreak [6,7].
This paper describes the early spread of influenza-like
illness (ILI) at Primary Care Trust (PCT) level during the
first phase of the 2009 influenza pandemic using data
from national syndromic surveillance systems, with
a particular focus on West Midlands and London, the
areas initially most affected, in order to identify the
point when sustained community transmission began.
Methods
HPA/NHS Direct surveillance system
NHS Direct is a 24-hour nurse-led telephone helpline
that provides health information and advice to the

Page 2

2www.eurosurveillance.org
general public [8]. To handle the calls, nurses use a
computerised clinical decision support system that
uses symptom-based clinical algorithms. Nurses
assign the call to the most appropriate algorithm
and the patient’s symptoms determine the questions
asked and the action to be taken following the call,
which could be guidance on self-care or referral to
their general practitioner (GP) or advice to attend a
hospital emergency department. Anonymised data on
the number of calls for key algorithms are sent to the
Health Protection Agency (HPA) Real-time Syndromic
Surveillance Team every day for surveillance pur-
poses. As the number of daily calls to NHS Direct var-
ies, indicators are expressed as the percentage of calls
for that algorithm using all NHS Direct calls as the
denominator. The algorithms for cold/flu, cough, fever,
and difficulty breathing were monitored during the
2009 influenza pandemic on a daily basis. Due to the
increasing number of calls received by NHS Direct an
additional ‘swine flu’ algorithm was introduced, which
was included in the cold/flu calls in order to capture all
pandemic related calls.
Call data for cold/flu were mapped by postcode district
in the West Midlands region, following an outbreak of
pandemic influenza A(H1N1)2009 in a primary school
[9], and also in London following an increase in the
number of cases in early June.
HPA/QSurveillance system
The HPA/QSurveillance system was set up by the
University of Nottingham and Egton Medical Information
Systems (EMIS; a supplier of general practice compu-
ter systems) in collaboration with the HPA [10,11]. Over
3,400 general practices with over 23 million patients
submit data to the QSurveillance database, covering
about 38% of the UK population. Aggregated data on
GP consultations for a range of indicators are automati-
cally uploaded daily from GP practice systems to a cen-
tral database. Consultation data are based on clinical
diagnoses that are recorded as codes on the practice
system. Indicators, for example ILI, are defined as col-
lections of clinical diagnosis codes. The surveillance
system usually produces weekly reports, but daily
reports were also provided throughout the pandemic
period. Data are available at national, regional and PCT
level.
Daily data for ILI, pneumonia, upper respiratory tract
infection (URTI), lower respiratory tract infection (LRTI),
ILI with antiviral drugs prescribed, and pneumonia with
antibiotics prescribed were monitored during the pan-
demic. Daily ILI data were mapped by PCT, initially only
for the West Midlands and London regions, and later
also for other regions when the local ILI rates increased.
Weekly mapping at PCT level was later extended to all
PCTs in England and continued through the second
pandemic wave during the winter of 2009/10.
Figure 1
NHS Direct cold/flu calls for West Midlands and London, summer 2009
0
5
10
15
20
25
30
35
21 22 23 242526 272829 303132 33 34
Week number in 2009
Percentage of cold/flu calls
NationalLondonWest Midlands

Page 3

3www.eurosurveillance.org
The ILI indicator is a group of clinical diagnosis codes
recorded by GPs during routine consultations and is
widely used as a proxy for community-based influ-
enza activity [12,13]. In order to compare ILI rates with
the seasonal influenza activity experienced in a nor-
mal winter season estimated thresholds for daily and
weekly HPA/QSurveillance data were developed and
used to interpret ILI data included in surveillance bul-
letins and PCT maps [11]. All maps were drawn using
MapInfo Professional version 9.5. In this paper data
are presented from week 21 in 2009 (week commenc-
ing 18 May), when the first school outbreak occurred in
Birmingham, to week 34 in 2009 (week commencing 17
August), when UK ILI rates returned to baseline activ-
ity, to demonstrate the progression of the first wave
of the influenza pandemic in the UK. This period coin-
cides with the treatment only phase of the outbreak
that began on 2 July (in week 27, the week commencing
29 June).
The HPA routinely analyse and monitor syndromic
data throughout the year. From the start of the pan-
demic the HPA Real-time Syndromic Surveillance Team
used daily outputs from the HPA/NHS Direct and HPA/
QSurveillance systems to monitor a range of indicators
that might suggest wider community transmission of
pandemic influenza A(H1N1)2009, and were also used,
along with laboratory data and local intelligence, to
help identify hotspots, areas of particularly high influ-
enza activity and of rapid increase in influenza rates.
Data at national, regional (Strategic Health Authority),
local health district (PCT), and postcode district level
were included in daily bulletins distributed to the HPA,
the Department of Health, the National Health Service
(NHS) and the Government.
Results
The first suggestion of community spread was seen in
the West Midlands region following an outbreak in a
primary school in the Heart of Birmingham PCT where
the first case of pandemic influenza A(H1N1)2009 was
confirmed during week 21, 2009 [9]. The cold/flu call
data from the HPA/NHS Direct system and the PCT
level data from the HPA/QSurveillance system showed
two distinct peaks of pandemic influenza activity in
the West Midlands (Figures 1 and 2). NHS Direct cold/
flu calls for the West Midlands showed an early rise
in calls that peaked in week 26 (week commencing
22 June). There was a second peak in both systems in
week 29 (week commencing 13 July). These peaks were
respectively four weeks and one week ahead of the
national peak in week 30 (week commencing 20 July). In
the HPA/QSurveillance system, GP consultation rates
for ILI showed that the early increase was accounted
for by four PCTs: Heart of Birmingham, where the ini-
tial school outbreak occurred, and the three surround-
ing PCTs, Birmingham East and North, Sandwell, and
South Birmingham. By week 26, all four had reached
exceptional levels of influenza activity (above 130
consultations per 100,000) except South Birmingham
which reached this level in week 27.
Community transmission in London started slightly
later and showed a different pattern, with HPA/NHS
Direct and HPA/QSurveillance systems both showing
a single peak in week 29, the same week as the West
Midlands peak, one week ahead of the national peak
(Figures 1 and 2). HPA/QSurveillance ILI rates reached
exceptional levels in the Tower Hamlets PCT and the
City and Hackney PCT in week 27, and the majority of
Figure 2
HPA/QSurveillance general prctitioner consultation rate
for influenza-like illness in Primary Care Trusts in the
West Midlands (A) and London (B), summer 2009
A
B
HPA: Health Protection Agency; ILI: influenza-like illness.
Indicative estimated thresholds for QSurveillance weekly
influenza-like illness data in the United Kingdom
HPA/QSurveillance system influenza-like illness thresholds
[11]: baseline influenza activity: below 20 per 100,000; normal
influenza activity: 20-70 per 100,000; above average influenza
activity: 70-130 per 100,000; exceptional influenza activity: ≥130
per 100,000
0
100
200
300
400
500
600
700
800
212223 2425
Week number in 2009
2627 2829 3031323334
ILI consultation rate per 100,000
Primary Care TrustsWest Midlands
United Kingdom
Normal seasonal influenza
Above average influenza activity
Exceptional influenza activity
Week number in 2009
ILI consultation rate per 100,000
Primary Care Trusts
London
United Kingdom
0
100
200
300
400
500
600
700
800
21222324252627282930 31323334
Normal seasonal influenza
Exceptional influenza activity
Above average influenza activity

Page 4

4www.eurosurveillance.org
Figure 3
Weekly HPA/QSurveillance consultation rates for influenza-like illness by PCT and cold/flu calls to the HPA/NHS Direct Syndromic Surveillance System by postcode district for West Midlands and London, summer 2009
Week 26 (22-28 June 2009)
West Midlands, QSurveillance
Week 29 (13-19 July 2009)
Week 34 (17-23-August 2009)

Page 5

5www.eurosurveillance.org
Week 26 (22-28 June 2009)
West Midlands, NHS Direct
Week 29 (13-19 July 2009)
Week 34 (17-23-August 2009)