Respiratory Archives 2009

Surveillance of influenza and other respiratory viruses in the United Kingdom: October 2008 to April 2009
E McLean , H Murdoch, A Reynolds, F Begum, D Thomas, B Smyth, A Elliot, H Zhao, J Ellis, D Fleming, A Lackenby, J Watson and R Pebody

Summary

Influenza activity in the United Kingdom (UK) started early and reached moderate levels during the 2008/09 season. Clinical indices peaked between late December 2008 and early January 2009 in England, Wales, Scotland and Northern Ireland. In England and Scotland activity exceeded baseline levels for several weeks, in Wales the threshold was not breached but consultation rates were higher than has been seen for several seasons and in Northern Ireland high rates were seen but thresholds were not set. Levels of virological detection reflected clinical activity. Influenza A (H3) was the predominant strain, very few influenza A (H1) or B were detected. During the season, outbreaks, mainly caused by influenza A, were reported in care homes, schools, hospitals and army barracks. A large number of excess deaths were observed, the highest number since 1999/2000.

During the 2007/08 season a strain of influenza A (H1) which is resistant to the anti-viral drug oseltamivir, due to the 274Y mutation, emerged. In the 2008/09 season few influenza A (H1) viruses were detected though the majority (99%) were found to carry this mutation. These viruses were first detected in the south west of England and, although others were detected from all over the UK , the majority (39%) were from the South West. Internationally most influenza A (H1) isolates were shown to be resistant to oseltamivir. In North America influenza A (H1) was the predominant circulating strain; in the USA 99.5% were resistant to oseltamivir.

The proportion of over 65 year olds in England who received the 2008/09 seasonal influenza vaccine reached 74.1%, an increase from 73.5% the previous year. For people aged between 6 months and 65 years who fall into a risk group, the proportion vaccinated increased from 45.3% in 2007/08 to 47.1% in 2008/09. In Scotland, the uptake in the 65 and over group, and those under 65 at-risk, was 76.3% and 48.5%, respectively. In Northern Ireland it was 76.8% and 74%, and in Wales, 59.5% and 40.8%.

In Europe, high levels of influenza were seen in many countries. Activity was first seen in western countries which then spread to eastern countries. The UK was one of the first countries affected, and activity here peaked earlier compared to other European countries. Throughout Europe influenza A (H3) was the predominant circulating strain.

Internationally, the H5N1 avian influenza virus continued to be detected in poultry and wildlife and cause sporadic cases in humans in China, Indonesia, Egypt, Viet Nam and Cambodia. There was an outbreak of low pathogenic influenza A (H6N1) in poultry in the east of England in February 2009.

In April 2009, a novel influenza A (H1N1) virus was recognised in the USA , the same virus was found to be linked to an increase in severe respiratory illness in Mexico. The virus quickly spread across the globe and the first two cases were identified in the UK on 27 April 2009. WHO declared it to be a pandemic on 11 June 2009. This report covers weeks 40/08 to 18/09 (week ending 03 May) and does not include data or information about the pandemic.

Introduction

In the UK, the activity of influenza and other respiratory viruses in humans is monitored throughout the year, but there is a particular focus on the winter season between October (week 40) and May (week 20). Data is collated from a variety of sources to provide information on circulating influenza strains for early detection of strains with epidemic potential, and to contribute towards the decision on influenza vaccine composition for the following year. Surveillance activities also produce timely reports on influenza activity and burden of disease for health professionals, the media and the public.

Methods

Influenza surveillance is dependent on both clinical and virological data collected from across the UK. The information sources have been previously described [1,2]. This season, reporting of surveillance information by several of these sources continued to be via the Department of Health funded Immform website (previously know as the Health Protection Informatics (HPI) website). The aim of submitting influenza surveillance data via the Immform site is to make the data available to relevant groups in a more timely way.

Results

Clinical surveillance data

England and Wales – Royal College of General Practitioners (RCGP)
The weekly General Practitioner (GP) incidence rate for influenza-like illness (ILI) exceeded the baseline level of 30 new episodes per 100,000 population in week 50/08 and peaked at 68.5 per 100,000 in week 51/08. A second peak of 51 per 100,000 was seen in week 01/09; the reduced rate in week 52 was most likely due to the holiday period (figure 1).

Figure 1: Weekly GP consultation rate for influenza-like illness, England and Wales (RCGP) 2008/09 and recent years

The highest rates were seen in people aged over 15 years and the lowest in the less-than-one-year age group. Peaks were seen in week 51/09 in the young and middle-age groups, the highest in the 15 to 44 year age group at 79.7 per 100,000. The rates in the 65 to 74 years (70.2 per 100,000) and over 75 years (65.6 per 100,000) age groups peaked later, in week 01/09 (figure 2).

RCGP ILI rates are also reported by region: north, central and south. The ILI rates started to increase first in the central and southern regions although the peak was observed in week 51/09 in all three regions; the highest rate was in the central region at 81.7 per 100,000, followed by the southern region (67.8 per 100,000) and the north (43.8 per 100,000), the latter had been consistently lower than the previous two for the entire season.

The overall rates for acute bronchitis also peaked in week 51/08 at 218.7 per 100,000. A different pattern was seen in the age groups; the younger age groups peaked earlier in week 47/08 (the under one-year-olds the highest at 694.8 per 100,000), the rates in people aged 15 to 74 peaked in week 51/08 and in the over 75-year-olds it was in week 01/09. The trends in the younger age groups are similar to that of the number of respiratory syncytial virus (RSV)-positive specimens reported by regional laboratories while in the older age groups the trends are similar to the number of influenza-positive specimens reported (data not shown).

Figure 2: Weekly GP consultation rate for influenza-like illness by age group, England and Wales (RCGP) 2008/09 by age group

Scotland - Health Protection Scotland
The Scottish GP Flu Spotter scheme has been collating reports of influenza-like illness during the winter season in Scotland for over 30 years. The scheme currently consists of weekly returns of estimated consultations for influenza-like illness from 90 practices in 13 NHS board areas covering around 7-8% of the Scottish population. In the 2008/9 season, the GP consultation rates within the GP Flu Spotter scheme for Scotland (figure 3) exceeded baseline levels (50/100,000) in week 51/08 and peaked at 92 per 100,000 in week 02/09, this was higher than the previous season's peak of 50/100,000 in week 02/08 but still lower than the peak in the 2006/07 season of 158/100,000 in week 02/07. The GP Flu Spotter rate for the 1999/2000 season is also included within figure 3 and shows a peak of activity of 848 per 100,000 population in week 02.

Figure 3: Weekly consultation GP rate for influenza-like illness per 100,000 population, Scotland (Flu Spotter scheme) 2008/09 and recent years

The Pandemic Influenza Primary Care Reporting (PIPeR) system was designed to meet the surveillance needs in the event of a pandemic of influenza developing. This system has three main components, two of which emulate existing systems for flu surveillance or vaccine monitoring. PIPeR was used over the course of the 2008/2009 season to generate influenza (and pneumococcal) vaccine uptake and provide trend data on clinical presentation with ILI and acute respiratory illness (ARI). In addition PIPeR generates clinical trend data for ILI and ARI presentations by age and clinical risk groups whilst reporting on the laboratory investigation of presentations using multiplex PCR testing of respiratory samples.

The average consultation rate in all ages peaked at around 65 per 100,000 population last winter (figure 4). This figure is similar to the previous year, although the peak consultation rate occurred slightly later in the season.

The peak consultation rates were in the 0-4 year age group with the 5-14 age group being the second highest. Peak consultation rates occurred slightly earlier in the 0-4 year age group than the other age group. The lowest consultation rates overall were in the 15-64 age group (figure 5).

Figure 4: Daily consultation rates (per 100k) for PIPeR practices, Scotland 2008/09 and 2007/08

Figure 5: Consultation rates for PIPeR practices by age group, Scotland 2008/09

Wales - National Public Health Service (NPHS Wales)
Consultation rates in the sentinel GP scheme in Wales remained within baseline levels (<25/100,000) for the duration of the season. The rate peaked a week later than in England, in week 52/08 at 21.5/100,000 (figure 3) which was higher and earlier than the peaks in the previous two seasons; 8.5 per 100,000 in week 01/08 and 17.8 per 100,000 in week 07/07 (figure 6).

Figure 6: Weekly GP consultation rate for influenza in Wales, 2008/09 and recent years

Northern Ireland - Communicable Disease Surveillance Centre (CDSC Northern Ireland)
The combined consultation rate for influenza and ILI showed a peak in week 51/08 at 196.5 per 100,000 and, after dropping in week 52, peaked again in week 01/09 at 204.9 per 100,000 which is higher than the peak of 64.5/100,000 in week 05/08 of the previous season and similar to the 2006/07 season peak of 204/100,000 in week 05/07 (figure 7). This is the ninth year of the enhanced surveillance scheme in Northern Ireland, provisional thresholds for the 2009/10 winter have been established as: <70 per 100,000 corresponding to baseline activity; 70-500 per 100,000 corresponding to 'normal seasonal activity'; and >500 as 'epidemic activity'. These thresholds are provisional and may be subject to change.

Figure 7: Weekly GP consultation rate for influenza/influenza-like illness in Northern Ireland, 2008/09 and recent years

* Provisional threshold proposed for use during 2009/10 winter

QSurveillance ® - HPA and Nottingham University Division of Primary Care
QSurveillance® is a collaborative national surveillance system coordinated by the University of Nottingham Division of Primary Care and the Health Protection Agency Real-time Syndromic Surveillance Team. The system comprises a network of general practitioners based across the UK. Morbidity codes are reported on a daily/weekly basis from each practice, which are aggregated to national/regional level and then reported as a series of clinical and prescribing indicators in the HPA QSurveillance® weekly bulletin (http://www.hpa.org.uk/hpr/infections/primarycare.htm). A regional breakdown of data is presented by Strategic Health Authority and Primary Care Trust (England), Local Health Board (Wales) and Health and Social Care Trust (Northern Ireland). There is currently no coverage of Scotland.

QSurveillance® is currently made up of 3454 practices in the UK, with a population of 23.7 million. The coverage of the QSurveillance® practices across the UK and devolved nations is described in table 1. Although the practices are located across the UK , the majority are based in England and Wales; the similarity of QSurveillance ® trends to those of RCGP (England and Wales) reflects this. Actual reported rates from QSurveillance ® were lower than those of RCGP; the peak in ILI in all ages was in week 51/08 at 42.7 per 100,000 compared to 68.5 per 100,000 from RCGP. Later peaks in week 01/09 in the older age groups were also seen, with the 65 to 74 year group peaking at 37.4 per 100,000 and the over 75 year group at 35.0 per 100,000. Country specific data for Northern Ireland from QSurveillance® showed a similar trend to that of CDSC Northern Ireland but with lower rates. For Wales however, the rates from QSurveillance ® were higher than those reported from the National Public Health Service in Wales, this may be due to a more specific case definition used by NPHS Wales. The country-specific rates for England were virtually indistinguishable from the overall UK rate. Data for Scotland are not used by QSurveillance ® . Thresholds for QSurveillance ® are being established.

Table 1: Demographics of QSurveillance® system across the UK

Country	No. practices	QSurveillance® population (millions)	National coverage (%)
UK	3454	23.7	38.9%
England	3357	23.1	45.2%
Scotland	0	-	-
Wales	42	0.3	10%
Northern Ireland	55	0.32	18.1%

 

Syndromic surveillance data

NHS Direct for England and Wales
The national proportion of NHS Direct 'cold/flu' calls for all ages exceeded the baseline threshold of 1.2% [3] in week 49/08 and peaked in week 51/08 at 2.1% (figure 8). The highest proportions of 'cold/flu' calls were among those aged 15 to 44 years at 2.8% in week 51/08 and 45 to 64 years at 2.7% in weeks 51 and 52/08 which was consistent with the age distribution for ILI incidence rates in the RCGP scheme. The national proportion of 'fever' calls in the 5 to 14 year age group also exceeded the baseline threshold of 9% in week 49/08 and peaked at 12.3% in week 51/08. Both measures exceeded baseline a week earlier than the RCGP consultation level, which provided early evidence for influenza circulation.

Figure 8: Proportions of calls to NHS Direct ( England and Wales ) for fever (5-14 year group) and cold/flu, 2007/08 and 2008/09

NHS 24 for Scotland
The proportions of calls for fever in the 5-14 year age group and for colds/flu in all ages peaked at higher levels in 2008/09 than in previous years; fever in 5-14 years at 15.5% in week 51 and cold/flu at 1.5% in week 52 (figure 9). Thresholds have not yet been set for data from NHS 24.

Figure 9: Proportions of calls to NHS 24 ( Scotland ) for fever (5-14 year group) and cold/flu, 2007/08 and 2008/09

Out-of-hours call centres in Northern Ireland
Enhanced surveillance of influenza/influenza-like illness was established in Northern Ireland in the autumn of 2000 based on a network of sentinel general practices. However unlike other areas of the UK there is no equivalent of NHS Direct/NHS24 to provide additional syndromic information particularly for consultations after hours or at weekends/public holidays.

During the 08/09 influenza season a pilot was undertaken with two of the seven primary care out-of-hours (OOH) centres. Data on total consultations and those for influenza/influenza-like illness, stratified by age, were extracted daily for the previous 24 hours and compared with sentinel consultation rates. This was by an auto-extraction process, with data being imported into a central repository with a front-end reporting function to generate reports.

Trends in OOH consultation data for influenza/influenza-like illness corresponded to those noted from the GP sentinel surveillance programme. As all OOH centres use the same clinical software this process is being rolled out to the other five OOH centres to enable daily reporting. In addition daily information is also being extracted on the type and outcome of consultation.

Virological surveillance data

A total of 1949 influenza viruses were detected at the HPA respiratory virus unit (RVU) at the Centre for Infections (CfI) between week 40/08 and week 16/09. The peak week for positive samples for influenza (combined figures from community and hospital sources submitted to RVU), was week 51/08, with 381 positives (364 of these were A (H3)). This correlates well with the peak week of clinical activity. The detection of influenza B was predominantly after the influenza A peak, though there was not one distinguishable peak: 17 were detected in weeks eight, nine and twelve.   Detections were made from samples from all regions of the UK (table 2).

Table 2: Number of influenza viruses detected by RVU between week 40/08 and 16/09 by region and subtype

Region	Subtype			Total
	H3	H1	B
East	248	2	27	277
East Midlands	168	8	9	185
London	330	10	54	394
North East	30	3	16	49
North West	181	10	35	226
South East	201	3	22	226
South West	141	38	13	192
West Midlands	107	4	5	116
Yorks. & Humberside	192	13	16	221
North'n Ireland	10	0	0	10
Scotland	26	7	2	35
Wales	10	6	0	16
Unknown region	0	1	1	2
Total	1644	105	200	1949

 

Virological surveillance in the community, including sentinel detection schemes
In total, RVU identified 947 positive community samples for influenza between week 40/08 and week 16/09. This figure is based on those respiratory specimens submitted directly to the RVU from the RCGP/HPA Community Surveillance Scheme, the HPA Virological Surveillance Scheme, and outbreaks. 86% were identified as influenza A (H3), 10% as influenza B and 4% as influenza A (H1). These detections were predominantly from those aged 15-44 years (51%) (figure 10).

Figure 10: Total number of detections of influenza by RVU by source of sample (hospital or community) and age group

There are two complementary surveillance schemes that use sentinel GPs to collect samples for virological analysis in England:

• RCGP/HPA Community Surveillance Scheme, in which a subset of GPs involved in the RCGP surveillance scheme send respiratory specimens directly to RVU for testing.
• HPA Virological Surveillance Scheme, in which GPs around the country send respiratory specimens from ILI patients to their regional laboratories for testing. The regional laboratories forward the results of all specimens tested to CfI and all influenza-positive specimens to RVU for confirmation and further typing.

Table 3 shows the surveillance data obtained via these two surveillance schemes and similar data provided by Northern Ireland, Scotland and Wales.

Table 3: Results from UK GP-based virological surveillance schemes, 2008/09

Country	Total samples tested	Samples positive for influenza (%)					Peak week	Samples positive in peak week
		All	A (untyped)	A(H3)	A(H1)	B
England (RCGP & RMN)	2780	950 (34.2%)	163 (5.9%)	655 (23.6%)	36 (1.3%)	96 (3.5%)	51/08	200/367 (54.5%)
North'n Ireland	191	80 (41.9%)	61 (31.9%)	4 (2.1%)	0	15 (7.9%)	01/09	23/32 (71.9%)
Scotland	566	104 (18.9%)	45 (8.0%)	29 (5.1%)	2 (0.4%)	31 (5.5%)	52/08	23/49 (46.9%)
Wales	94	17 (18.1%)	6 (6.4%)	7 (7.5%)	2 (2.1%)	2 (2.1%)	51/08	5/13 (38.5%)

Influenza A (H3) was the predominant virus type isolated from community samples throughout the UK . All the sentinel GP schemes indicated that influenza A dominated early in the season and that there was some influenza B activity afterwards. In England the peak number of samples was in week 51/08, the same week of the peak of clinical activity, though the peak of the proportion of samples positive was one week later in week 52/08 (figure 11). In Wales the peak week for positivity from the sentinel scheme was one week later than the clinical peak, in Scotland the clinical peak was a couple of weeks after the positivity peak and the two peaks coincided in Northern Ireland, though it should be taken into account that data from Northern Ireland is based on the week the sample was tested, rather than the week it was taken.

Figure 11: Number and proportion of specimens positive for influenza in two English sentinel virological schemes (RCGP/HPA and HPA/RMN, 2008/09

Reports of influenza infection from hospital laboratory reporting

Laboratory reports (NHS and HPA) by week of specimen indicated there were 1786 confirmed influenza A infections between week 40/08 and 16/09, peaking in week 51/08 with 326. Of the total, 381 were detected by serological test methods. There were 304 confirmed influenza B infections during this same period, peaking in week 08/09 with 26. Sixty-eight of these were detected by serological test methods.

Between week 40/08 and week 16/09, the RVU identified 1002 hospital samples as positive for influenza. A similar break-down by subtype was seen as in the community samples: 83% were identified as influenza A (H3), 10.5% as influenza B and 6.5% as influenza A (H1). These detections were mainly from children aged less than five years (47.5%) (figure 10).

Virus characterisation and vaccine match
A total of 677 viruses were characterised at RVU in the 2008/09 season. All influenza A (H3) viruses (527) were characterised as A/Brisbane/10/2007 H3N2-like and all influenza (H1) viruses (58) were characterised as A/Brisbane/59/2007 H1N1-like, both of which were strains in the 2008/09 seasonal influenza vaccine. Ninety-eight influenza B viruses were characterised, the majority of which (92) were B/Malaysia/2506/2004-like and the remaining six B/Florida/4/2006-like, the latter was a component of the 2008/09 influenza vaccine.

Antiviral resistance
Testing of influenza viruses for susceptibility to antiviral drugs is carried out at RVU. In the 2008/09 season, 99 % (90/91) of tested A (H1N1) viruses were resistant to oseltamivir. These viruses retained sensitivity to zanamivir and amantadine. The first resistant virus was detected from a sample taken in week 40 and these viruses were detected up to week 10. The one sensitive virus was detected from a sample taken early, in week 41. Resistant viruses were detected in most regions of the UK , though the majority (including the first detections) were from the south west of England (table 4).

All of the 231 influenza A (H3) isolates tested were found to be resistant to amantadine but sensitive to oseltamivir and zanamivir. Forty-four influenza B isolates were tested and all were sensitive to oseltamivir and zanamivir.

Table 4: Number of influenza A (H1) isolates tested for susceptibility to oseltamivir at RVU, by region

Region	Resistant	Sensitive	Not tested	Total
East	2	0	0	2
East Midlands	6	0	2	8
London	7	1	2	10
North East	3	0	0	3
North West	8	0	2	10
South East	3	0	0	3
South West	35	0	3	38
West Midlands	3	0	1	4
Yorks. & Humberside	13	0	0	13
North'n Ireland	0	0	0	0
Scotland	6	0	1	7
Wales	4	0	2	6
Unknown region	0	0	1	1
Total	90	1	14	105

 

Other viruses
In total, 80 specimens were positive for RSV from the two English GP sentinel virological surveillance schemes (RCGP/HPA and HPA/RMN). Seventy-one samples from the HPA/RMN scheme were positive for other viruses; Adenovirus (12), coronavirus (3), enterovirus (4), hMPV (15), parainfluenza (3), and rhinovirus (34). Five samples were positive for both an influenza and another virus and one sample was positive for influenza A, RSV and another virus.

The level of RSV activity according to the number of positive specimens at NHS and HPA regional laboratories was similar to the previous year and peaked in week 48/08 (figure 12).

Figure 12: Number of respiratory specimens positive for adenovirus, influenza A and B, parainfluenza, respiratory syncytial virus (RSV) and rhinovirus at HPA/NHS laboratories from 2004 to 2009 (week 16)

Mortality in England and Wales (Office of National Statistics (ONS))

The estimated number of weekly all-cause and all-respiratory causes registered deaths are provided by ONS. The weekly total number of estimated registered deaths due to all causes peaked at 15,233 in week 02/09 (figure 13), due to a time lag between time of death of registration this peak corresponds well to the RCGP ILI rate peak in week 51/08 and the peak weeks of acute bronchitis activity in people aged over 75 in week 51/08 and 01/09. This peak was higher than for the previous season (11,954 in week 03/08). The weekly number of total respiratory deaths also peaked in week 02/09 at 3334 but the highest percentage of respiratory deaths was seen in week 01/09 when 22.4% of deaths (3035) were due to respiratory disease.

The annual estimate of excess all-cause mortality is calculated using a time series model which uses 20 previous years' data to establish a baseline figure of expected deaths for the time of year [4]. Each year it is revised to incorporate data from the current season and the fitted model provides a figure for the most recent season and readjusts the previous years' figures. Excess deaths were first seen in week 50/08 and in the whole season 10,351 extra deaths were estimated (table 5). This is a large increase compared to the previous year when 426 excess deaths were observed and is the highest excess observed since 1999/2000 when there were 21,437 excess deaths. There were also high ILI rates observed in the 1999/00 season. It should be noted that the excess is due to all causes so cannot be directly attributed to influenza. The pronounced troughs in figure 13 during the 2008/09 season and other seasons are likely to be as a result of public holidays in which registry offices are shut. Increases the following week are likely to be in part due to registering 'rebound'.

Figure 13: Deaths by all causes, England and Wales 2008/09 (by week of registration)

Table 5: Estimated excess winter mortality in England and Wales , by influenza season

Season	Estimated number of excess deaths	95% Confidence Interval
1988/1989	1,480	932 - 2,027
1989/1990	27,959	27,138 - 28,781
1990/1991	8,627	7,806 - 9,537
1991/1992	6,085	5,537 - 6,632
1992/1993	1,646	1,373 - 1,920
1993/1994	14,174	13,353 - 14,995
1994/1995	2,031	1,531 - 2,578
1995/1996	15,397	14,576 - 16,218
1996/1997	21,140	20,592 - 21,688
1997/1998	0	0
1998/1999	17,330	16,782 - 17,877
1999/2000	21,437	20,889 - 21,984
2000/2001	842	568 - 1,116
2001/2002	6,922	6,648 - 7,196
2002/2003	6,492	6,219 - 6,766
2003/2004	5,139	4,591 - 5,686
2004/2005	1,965	1,692 - 2,239
2005/2006	0	0
2006/2007*	0	0
2007/2008	426	64 - 974
2008/2009	10,351	9,990 - 10,899

* Data missing from 2006/07 season.

Mortality in Scotland (Health Protection Scotland)

The number of deaths (by date of death) peaked at the end of December in Scotland , slightly earlier than the peak of influenza activity according to the GP ILI consultation rate. Expected numbers of deaths due to all causes in Scotland are estimated using two models. In December 2009 an excess was observed (figure 14), which is estimated to be greater than 500 according to both models. The greatest excesses were observed in the older age groups and in females (table 6).

Figure 14: Deaths due to all-causes in Scotland 2008/09 (by date of death)

Table 6: Observed, expected and estimated excess number of deaths in December 2008 by age and sex, Scotland

	Observed number of deaths	Expected		Excess
		Serfling	GAMS	Serfling	GAMS
Total	5562	5023.5	5041.7	538.5	520.3
Age group
0-14	34	33.6	27.6	0.4	6.5
15-44	234	218.0	215.4	16.0	18.6
45-64	735	746.4	770.3	-	-
65-74	1086	946.7	954.5	139.3	131.5
75-84	1773	1605.3	1615.9	167.7	157.1
85+	1700	1473.6	1458.1	226.4	241.9
Sex
Female	3003	2647.5	2633.6	355.6	369.4
Male	2559	2376.1	2408.0	182.9	151.0

Outbreaks

The Centre for Infections received 71 reports of acute respiratory illness outbreaks from across the UK, which is higher than in previous seasons. Almost all were from England (one from Wales and one from Northern Ireland). Most (57%) were from care homes (mainly affecting those aged over 65 years) with 30% from schools and the remainder from hospital wards (five), army barracks (three) and a university (one). In 57 of the outbreaks, respiratory samples were taken for testing and of these, influenza A was detected in at least one sample for 43 (75%) outbreaks and influenza B from six. One outbreak was confirmed as human metapneumovirus, one as rhinovirus and three as respiratory syncytial virus. Deaths were reported associated with six outbreaks (four care homes, two hospital wards); a total of 21 deaths were reported.

Uptake of seasonal influenza vaccine

In England, the uptake of seasonal influenza vaccine is monitored by HPA on behalf of the Department of Health. Vaccine uptake for those aged 65 years and over increased from 73.5% in 2007/08 to 74.1% in 2008/09. Out of 152 Primary Care Trusts taking part in the seasonal flu vaccine uptake collection, 148 achieved uptake rates of 70% or more. For people aged between six months to 65 years falling in a clinical risk group, the proportion vaccinated increased from 45.3% in 2007/08 to 47.1% in 2008/09 [5].

The vaccine uptakes rates for England, Northern Ireland, Scotland and Wales are shown in table 7.

Table 7: Vaccine uptake in the UK 2008/09 season

Country	England	Northern Ireland	Scotland	Wales
Proportion vaccinated 65+ years	74.1%	76.8%	76.3%	59.5%
Proportion vaccinated 6 months - 65 years (at risk)	47.1%	74.0%	48.5%	40.8%
Response rate*	96.2%	88.0%	-	92.2%

 

Influenza activity elsewhere in Europe [6]

Consultation rates for ILI and/or ARI rose above baseline levels in most European countries, starting in week 49/08. There was a general west to east progression, with high rates still being reported in one Russian region as late as week 15/09. High influenza activity was reported in 15 countries in total. The highest rates were generally seen in the 0-4 and 1-4 year age groups but Ireland, UK, Norway and Romania reported their highest rates in the 15-64 year age group. From week 40/08 to week 18/09 30,760 virus detections (sentinel and non-sentinel) were reported: 25,674 (84%) influenza A (11,702 H3, 1408 H1 and 12660 not sub-typed) and 4990 (16%) influenza B. The number of influenza A detections peaked in week 04/09 and that of influenza B in weeks 10 and 11/09. 3696 viruses were characterised; 2564 (69%) were reported as A/Brisbane/10/2007 (H3N2)-like, 166 (4%) as A/Brisbane/59/2007 (H1N1)-like, 30 (1%) as B/Florida/4/2006-like (B/Yamagata/16/88 lineage) and 935 (25%) as B/Malaysia/2506/2004-like (B/Victoria/2/87 lineage). Of the influenza B viruses the majority (95%) were B/Victoria lineage which was not included in the 2008/09 vaccine. Most other viruses characterised were similar to the other components of the vaccine. As there were few influenza B viruses overall, the mismatch with the vaccine is unlikely to have been of much public health importance. The majority (98%) of influenza A (H1) viruses tested were resistant to oseltamivir, reflecting the situation seen in the UK .

 

Avian influenza (H5N1) in humans and animals

During 2008, the number of new human cases of avian influenza A(H5N1) virus infection continued to increase as did the number of associated deaths globally. Since the beginning of the outbreak in 2003, 15 countries had confirmed cases: Azerbaijan, Bangladesh, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Lao People's Democratic Republic, Myanmar, Nigeria, Pakistan, Thailand, Turkey and Viet Nam. As of 1 July 2009, 436 human cases were reported of which 262 (60%) were fatal [7]. Egypt reported an increase in the number of confirmed cases at the beginning of 2009, in the first six months of 2009 30 cases were reported from Egypt; the highest number previously report for a full year was 25 in 2007. China and Vietnam also continued to report new cases and deaths in 2009.

During the 2008/09 season, outbreaks of avian influenza A(H5N1) in animals continued to be reported from Asia, Middle East, Africa and Europe. Fifteen countries reported new animal cases in 2008 (figures as of 21 July 2009), of which one was in Europe (Germany) [8].

Avian influenza (H6N1) in poultry in the UK

On 26 February 2009, the Department for the Environment, Food and Rural Affairs (Defra) confirmed avian influenza infection in poultry on two premises in the East of England, and on 27 February Defra confirmed that it was an avian influenza A (H6N1) virus. On 05 March 2009, Defra reported that further laboratory tests had confirmed that the H6N1 avian influenza virus was of low pathogenicity [9].

Pandemic influenza A (H1N1) 2009

At the end of April 2009 the USA reported the discovery of a novel influenza A (H1N1) virus [10,11]. It was discovered that the same novel virus had been causing an increase in respiratory illness and associated deaths in Mexico. The virus spread quickly across the globe, the first detection in Europe was in Spain with the first UK cases detected shortly afterwards on 27 April in a couple returning from Mexico. On 11 July, the World Health Organisation (WHO) increased the pandemic alert to the highest level [12].

Vaccine recommendations

The WHO recommended that the components for the 2009/10 seasonal influenza vaccine for the northern hemisphere should contain the following [13]:

• An A/Brisbane/59/2007 (H1N1)-like virus*
• An A/Brisbane/10/2007 (H3N2)-like virus *
• A B/Brsbane/60/2008-like virus

* A/Brisbane/59/2007 and A/Brisbane/10/2007 were 2008/09 vaccine viruses.

A pandemic influenza vaccine is also recommended for use in the 2009/10 season.

Conclusions

The 2008/09 season was moderate as influenza activity levels peaked earlier and higher than in several previous seasons. Adults were affected more than children, with several outbreaks in nursing/care homes recorded. The main circulating virus was influenza A, predominantly influenza A/Brisbane/10/2007 (H1N3)-like. There was very little influenza B activity, and this occurred towards the end of the season. This was a trend reflected throughout Europe.

Confirmed infections of RSV followed the established seasonal pattern during the 2008/09 season, which is characterised by a gradual increase in detections from mid-October, reaching a peak in December. The peak number and total number of detections this year was similar compared with the previous season.

Acknowledgements

The authors are grateful to all microbiologists, consultants in communicable disease control, infection control nurses, and GPs, especially those within the primary care networks, for their contribution to the surveillance schemes. We are appreciative to Joy Field and Praveen Sebastian Pillai at the CFI for their administrative and technical support. Thanks are also due to colleagues at the HPA respiratory virus unit, the HPA Primary Care Unit West Midlands, the Royal College of General Practitioners research and development centre, Health Protection Scotland, NPHS Wales and CDSC Northern Ireland for contributing data to this report.

References

1. Goddard NL, Joseph CA, Zambon M, Nunn M, Fleming D, Watson JM. Influenza surveillance in the United Kingdom: October 2000 to May 2001. CDR Wkly 2001; 11(CDR Suppl):1-7.

2. Mook P, Joseph CA, Ellis J, Zambon M, Fleming DM, Watson JM.  Surveillance of influenza and other respiratory viruses in the United Kingdom: October 2006 to May 2007. Health Protection Report 2008 Supplement. Available at: http://www.hpa.org.uk/hpr/archives/2008/hpr2308.pdf.

3. Cooper DL, Verlander N, Joseph C, Elliot AJ, Smith GE. Can syndromic thresholds provide early warning of national influenza outbreaks? J Public Health. Advance Access published on November 20, 2007. Available at: http://jpubhealth.oxfordjournals.org/cgi/content/full/fdm068v1

4. Serfling RE. Methods for current statistical analysis of excess pneumonia-influenza deaths. Public Health Reports 1963; 6:494-506.

5. The 2008/09 Influenza Vaccine Uptake Annual Report written by the Health Protection Agency (HPA) and commissioned by the Department of Health (DH). Available at: http://www.immunisation.nhs.uk/Professional_Information/Key_vaccine_information/Flu

6. Euroflu - Weekly Electronic Bulletin, 08 May 2009, Issue Number 304. Available at: http://www.euroflu.org/cgi-files/bulletin_v2.cgi

7. World Health Organisation, avian influenza information (accessed 21 July 2009). Available at: http://www.who.int/csr/disease/avian_influenza/country/cases_table_2009_07_01/en/index.html

8. World Organisation for Animal health - Update on highly pathogen avian influenza in animals (type H5 and H7) - accessed 21 July 2009. Available at: http://www.oie.int/downld/AVIAN%20INFLUENZA/A_AI-Asia.htm

9. Heath Protection Agency Avian influenza news - Low pathogenic H6N1 confirmed in poultry in the East of England - 05 March 2009. Available at: http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1230540082173?p=1202115495203#18

10. World Health Organisation - Recommended composition of influenza virus vaccines for use in the 2009-2010 northern hemisphere influenza season. Available at: http://www.who.int/csr/disease/influenza/recommendations2009_10north/en/index.html

11. World Health Organisation - DG Statement following the meeting of the Emergency Committee 11 July 2009. Available at: http://www.who.int/csr/disease/swineflu/4th_meeting_ihr/en/index.html

12. Centers for Disease Control and Prevention (CDC). Outbreak of swine-origin influenza A (H1N1) virus infection - Mexico, March-April 2009. MMWR Morb Mortal Wkly Rep 2009; 58 :467-70.

13. Centers for Disease Control and Prevention (CDC). Swine influenza A (H1N1) infection in two children-- Southern California, March-April 2009. MMWR Morb Mortal Wkly Rep 2009; 58 :400-2.

Legionnaires' disease in residents of England and Wales: 2007
FC Naik, KD Ricketts, TG Harrison, CA Joseph

Abstract

Four hundred and forty-two cases of Legionnaires' disease in residents of England and Wales, with onset of symptoms in 2007, have been reported to the national surveillance scheme. Over half of these cases (231) were acquired in the community, 12 were hospital acquired and the remaining 199 cases were associated with travel, either abroad or in the United Kingdom. The highest proportion of cases were diagnosis by urinary antigen detection. Twenty-four outbreaks/clusters were detected: 10 associated with community acquired infection, one associated with a hospital and 13 with clusters/outbreaks abroad. An overall case fatality rate of 12% was reported.

Introduction

Cases of Legionnaires' disease, a bacterial infection characterised by pneumonia, have been reported to the National Surveillance Scheme for Legionnaires' disease in residents of England and Wales since its establishment at the PHLS Communicable Disease Surveillance Centre (CDSC) in 1979. In 2003 the scheme was transferred to the Health Protection Agency, Centre for Infections (HPA, CfI) from where it is now administered. From 1980 to 1999 between 111 and 280 cases were reported each year. There has since been a notable rise in case numbers, reaching a high of 551 cases in 2006. Between 1980 and 2007 a total of 6391 cases have been reported to the surveillance scheme. Forty-eight percent of these cases originate from within the community, 41% are associated with travel abroad, 6% travelled within the UK and the remaining 5% are considered hospital acquired. This paper describes the epidemiology of cases with onset of symptoms in 2007.

Methods

Diagnosed cases of Legionnaires' disease are reported to local Health Protection Units (HPUs). Healthcare workers are then asked to obtain a 14 day history of the case's movements, prior to onset of symptoms, to identify risk factors and possible sources of infection and then to complete a national surveillance scheme reporting form which provides clinical, epidemiological and microbiological details for each case.

The Atypical Pneumonia Unit within the HPA CfI Respiratory and Systemic Infections Laboratory (RSIL) provides confirmatory diagnostic testing of reported cases. It uses an in-house enzyme immuno-assay (EIA) test on urine samples, and carries out immunofluorescence antibody testing (IFAT) on serum samples (in the presence of campylobacter blocking fluid to eliminate cross reaction). Positive isolates can be sub-typed, using sequence based typing, to further differentiate the Legionella strain. In appropriate circumstances Polymerase Chain Reaction (PCR) can be carried out for the detection of L. pneumophila DNA [1].

Reported cases that meet the case definitions (table 1) are entered onto the national database where they are checked for links in time and/or place with previous cases. Travel associated cases are reported to the European Surveillance Scheme for Travel Associated Legionnaires' disease (EWGLINET) [2].

Table 1: HPA case definitions for legionella infections [3]

CATEGORY	CASE DEFINITION
Confirmed Case	Clinical or radiological evidence of pneumonia and a microbiological diagnosis by culture of the organism from respiratory specimens, a four-fold rise in serum antibody levels* against L. pneumophila serogroup 1, or detection of L. pneumophila antigen in urine.
Presumptive Case	Clinical or radiological evidence of pneumonia and a microbiological diagnosis of a single high antibody level* against L. pneumophila serogroup 1 antigen or a seroconversion (a four fold rise or greater)* against L. pneumophila non-serogroup 1or other legionella species.
Hospital Acquired (Nosocomial) Case	1. Definitely nosocomial: Patients who spent all of the 10 days in hospital before onset of symptoms. 2. Probably nosocomial: Patients who spent between one and nine of the 10 days in hospital prior to onset of symptoms and either a) became ill in a hospital associated with one or more cases of Legionnaires' disease, or b) yielded an isolate that was indistinguishable by monoclonal antibody (mAb) subgrouping, or by molecular typing methods from isolates obtained from the hospital water system at about the same time. 3. Possibly nosocomial: Patients who spent between one and nine of the 10 days prior to onset of symptoms in a hospital not known to be associated with any other cases of Legionnaires' disease and where no microbiological link has been established between the infection and the hospital.
Travel Associated Case	One or more overnight stays in holiday accommodation in the UK or abroad in the 2-10 days before onset of illness.
Travel Associated Cluster	Two or more cases that stayed at the same accommodation in the 2-10 days before onset of illness and within the same two years.
Community Cluster	Two or more cases linked by area of residence or work, or places visited and sufficient proximity in dates of onset of illness to warrant further investigation**.
Community Outbreak	Community clusters for which there is strong epidemiological evidence of a common source of infection, with or without microbiological evidence, and in response to which control measures have been applied to suspected sources of infection.

* When submitted to the Respiratory and Systemic Infections Laboratory, all positive serum specimens are examined by the IFAT test in the presence of campylobacter blocking fluid, to eliminate cross reactions.
** This is a working definition: the decision to follow up cases is made locally.