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Volume 3 No 29; 24 July 2009

Group A streptococcal infections: fourth update on seasonal activity, 2008/09

The current level of group A (Streptococcus pyogenes) streptococcal infections remains above that seen in recent years, despite seasonal declines that have been noted since May. This persistence of increased GAS activity during the emergence of swine influenza A(H1N1v) raises concern for the coming season.

Scarlet fever

Between week 37 of 2008 and week 28 of 2009, 3929 unconfirmed notifications of scarlet fever were made in England, making this the highest season since 1995/6 when 4536 notifications were made for the same period. Seasonal activity peaked in week 12 of 2009, with 235 notifications made for this week, the highest single weekly count since 1993. Notifications fell steeply after week 14 and currently similar to last year's figures.

Notifications of scarlet fever in Wales were also elevated compared to recent years, 110 between weeks 48 of 2008 to week 28 of 2009, compared to between 56 and 82 for the previous five seasons. Within England, notifications were elevated throughout the country, in particular the East of England, London, the South East, and the West Midlands, where notifications were two to three times higher than the average of the past five seasons.

Invasive group A streptococcal infection

Routine laboratory reports of invasive group A streptococcal (iGAS) infection, defined as the isolation of GAS from a normally sterile site, from across England, Wales and Northern Ireland continued to show increased numbers of cases throughout the winter and spring, peaking at week 52 of 2008 (48 reports) and again around week 12 of 2009 (48 reports). Numbers of cases have since fallen to be in line with the usual seasonal pattern, although remaining slightly elevated compared to recent years. A provisional 1012 reports of iGAS were made between week 37 of 2008 and week 20 of 2009, compared to between 712 and 887 reports for the same period in the previous four years, and just below 2003/04 (1108), the last peak year for iGAS. The addition of late reports will further increase the total for this season.

In contrast to England, numbers of iGAS reports for Northern Ireland and Wales have not shown any overall elevation between October 2008 and May 2009. Within the English regions, the following all showed elevated activity between October and May compared to the previous four (or more) seasons: East Midlands, London, North East, North West, South East, South West. Reports for the other regions were within the range seen since the last peak year, although further late reports may change that position.

Numbers of iGAS isolates referred to the Respiratory and Systemic Infection Laboratory at CfI from laboratories in England, Wales and Northern Ireland showed a similar trend to routine laboratory reporting, and remain elevated compared to the 2007/08 season. The emm /M-type distribution shifted over the course of the season, with marked fluctuations in emm /M3, which became strongly dominant in January (41% of isolates) and April (38%) 2009, although these have since decreased to ≤20%. The predominant emm/ M types remain as emm 1, 3 and 89.

Preliminary analysis of data captured from the enhanced surveillance for severe group A streptococcal infections has not identified any increase in cases in any particular risk group [1], although the proportion of infections in children is higher than the last period of enhanced surveillance, 22% vs 15% in 2003-04; injecting drug users were removed from this analysis given their dominance in 2003-04 [2]. The most common acute risk factors reported were skin lesion (17%), recent childbirth (4%) and varicella infection (3%). Just over a third (37%) of cases had no underlying illness or co-morbidity, with following conditions noted amongst the remainder: chronic heart disease (10%), diabetes (9%), malignancy (6%), immunosuppression (5%), and renal disease (5%). 

A common and diverse range of clinical presentations have been reported, with cellulitis the most common presenting symptom for iGAS infection (24%) followed by pneumonia (10%), septic arthritis (8%) and necrotising fasciitis (5%). Nineteen per cent of cases were admitted to an intensive care or high-dependency unit. The case fatality rate derived from these preliminary data appears to be elevated, currently estimated at 23% within seven days of diagnosis, although outcome information is still awaited for a third of cases.

Preliminary results from the enhanced surveillance suggest a generalised increase in invasive group A streptococcal diseases, and as such it remains unclear why this increase, along with increases in scarlet fever, should have arisen. Although analysis of isolates submitted to the national reference laboratory has not identified any unusual serotypes to be circulating, the significant increase of emm/M3 is of concern in view of the association of this serotype with more severe clinical presentations compared to other emm types [3,4]. Molecular studies are currently underway to determine the virulence profiles of the emm/ M3 strain in particular.

Given the emergence of swine influenza A (H1N1v) and concerns over the potential impact of secondary bacterial infections [5], enhanced surveillance will be continued until the end of the calendar year, with a decision on the further continuance to be made at that time. At present, 8% of severe GAS infections were noted as having had a flu-like illness over the past 14 days. This will be monitored closely along with changes in the proportion of children and young adults affected and the proportion of cases presenting with pneumonia as a means of identifying any emerging impact of H1N1v.

Microbiologists and HPU staff are requested to continue completing questionnaires for all cases meeting the case definition for severe GAS infection diagnosed from specimens taken since 1 January 2009. The enhanced surveillance protocol and questionnaires can be downloaded from the HPA web site [6].

Clinicians, microbiologists and HPUs should be mindful of the continued heighted activity for iGAS and maintain a high index of suspicion in relevant patients, including patients with flu-like illness, as early recognition and prompt initiation of specific and supportive therapy can be life-saving [7]. Invasive disease isolates and those from suspected clusters or outbreaks should be submitted to the SDRU, Respiratory and Systemic Infection Laboratory at the Health Protection Agency, Centre for Infections, 61 Colindale Avenue, London NW9 5HT.

Guidelines for the management of close community contacts of invasive group A streptococcal disease are available on the Agency's website [8].

References

1. HPA. Enhanced surveillance initiated for group A streptococcal infections. Health Protection Report [serial online] 2009; 3(8): news. Available at: http://www.hpa.org.uk/hpr/archives/2009/hpr0809.pdf.

2. Lamagni TL, Neal S, Keshishian C, Hope V, George RC, Duckworth G et al. Epidemic of severe Streptococcus pyogenes infections in UK injecting drug users, 2003-04. Clin Microbiol Infect 2008; 14(11): 1002-1009.

3. O'Loughlin RE, Roberson A, Cieslak PR, Lynfield R, Gershman K, Craig A et al. The epidemiology of invasive group A streptococcal infection and potential vaccine implications: United States, 2000-2004. Clin Infect Dis 2007; 45(7): 853-862.

4. Lamagni TL, Neal S, Keshishian C, Alhaddad N, George R, Duckworth G et al. Severe Streptococcus pyogenes Infections, United Kingdom, 2003-2004. Emerg Infect Dis 2008; 14(2): 201-209.

5. Morens DM, Taubenberger JK, Fauci AS. Predominant role of bacterial pneumonia as a cause of death in pandemic influenza: implications for pandemic influenza preparedness. J Infect Dis 2008; 198(7): 962-970.

6. National enhanced surveillance of severe group A streptococcal disease: protocol (PDF, 289 KB). Downloadable from: http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1234859706309?p=1202487092497

7. Increase in invasive group A streptococcal infections in England. Department of Health 2009; CEM/CMO/2009/05 [cited 1 April 2009]. Available at: https://www.cas.dh.gov.uk/ViewandAcknowledgment/ViewAlert.aspx?AlertID=101179.

8. Health Protection Agency Group A Streptococcus Working Group. Interim UK guidelines for management of close community contacts of invasive group A streptococcal disease. Commun Dis Public Health 2004; 7(4): 354-361.

Recent staphylococcal foodborne outbreaks

Over the past two months two separate staphyloccoccal foodborne outbreaks have been reported. This particular type of foodborne disease results from the ingestion of staphylococcal enterotoxins that are preformed in foods by enterotoxigenic strains of coagulase-positive staphylococci, mainly Staphylococcus aureus. The principle symptom is vomiting which occurs 1-6 hours after ingestion of contaminated food and this is usually followed by diarrhoea. In cases with severe symptoms dehydration and collapse may occur, although, more usually, full recovery is within 24 hours. In most outbreaks it is a food handler who has contaminated the food which has then been stored at a temperature that permits the staphylococci to grow to high levels (>105cfu/g) and enterotoxin to be produced. S. aureus is destroyed by adequate cooking but the enterotoxins are heat stable and able to withstand cooking procedures including boiling. Staphylococcal food poisoning is highly seasonal with most outbreaks occurring in the summer when temperature control of food can be more difficult.

The first outbreak occurred in late May of this year at a church function and involved the consumption of paella containing cooked shellfish and rice. Twenty of 25 people suffered from vomiting and diarrhoea within 1-2 hours of eating the paella which had been held at ambient temperature for several hours before being reheated and served. Laboratory testing found S. aureus at high levels in the paella (106cfu/g). Additionally the strain isolated contained Staphylococcus entertoxin genes sea , seg and sei, indicating the potential of the organism to produce staphylococcal enterotoxins. Moreover, staphylococcal enterotoxin A was detected directly from the paella.

The second outbreak involved 200 members of the police force who were on duty policing a demonstration in early July, of whom 47 (24%) suffered from staphylococcal food poisoning. Locally prepared sandwiches were stored unrefrigerated in a van before being consumed on what was one of the hottest days of the summer. Symptoms of vomiting and diarrhoea were experienced 30-60 minutes after sandwiches were consumed and ten of the cases were taken to hospital. Staphylococcal enterotoxin A was detected in one of the sandwiches (chicken and sweetcorn mayonnaise) and high numbers of S. aureus (>104cfu/g) containing the entertoxin genes se a and seh , and of phage type A, were isolated from a number of sandwiches with different fillings and also from faecal specimens from cases. The same strain of S. aureus was also present in a range of environmental swabs taken from the premises where the sandwiches were made including the interior of a fridge, a can opener and dish cloth, as well as from an infected skin lesion on the hand of a person involved in the sandwich preparation.

Whilst staphylococcal foodborne outbreaks are reported infrequently in the UK, partly due to the relatively mild and short duration of symptoms, these two recent outbreaks serve to highlight the importance of both good hygiene practice and appropriate temperature control and storage of foods, as preventative measures against staphylococcal food poisoning. The microbiological investigations performed at two HPA RMN Food Water and Environmental Microbiology Laboratories (London and Birmingham), together with the Foodborne Pathogen Reference Unit (Laboratory of Gastrointestinal Pathogens) and the Laboratory for Healthcare Associated Infections, at the HPA Centre for Infections, London, were invaluable in providing evidence of staphylococcal food poisoning and confirmed the source of contamination enabling corrective action to be taken.

Trends in diagnoses of sexually transmitted infections in the UK: update for 2008

The 2009 annual update of UK statistics on incidence and prevalence of sexually transmitted diseases, covering cases reported up to the end of 2008, has been published on the HPA website [1].

The 2009 update includes more extensive data than in previous years. It is derived from reports on all new STI episodes seen at genitourinary medicine (GUM) clinics in the United Kingdom over the period 1999-2008, and, for the first time, also includes data on chlamydia diagnoses reported from other clinical settings for 2008.

A more detailed analysis of genital herpes and genital warts diagnoses will be included in next week's HPR.

Key points from the 2008 data

  • In 2008, numbers of new diagnoses of gonorrhoea and syphilis in UK GUM clinics appeared to be in decline or stabilising, although for syphilis numbers were still much higher than 10 years ago
  • Over the same period, new diagnoses of genital herpes and genital warts continued to rise, although the recent rapid increase in diagnoses of genital herpes probably reflects increased use of sensitive molecular tests
  • Genital chlamydial infection remained the most commonly diagnosed STI in the UK. Substantial and increasing numbers of chlamydia diagnoses are made in community-based settings outside of GUM clinics, associated with improved access to testing. In 2008, there were over 200,000 chlamydia diagnoses reported in the UK, including those made outside the GUM clinic setting
  • Recent modest improvements in sexual health should be built upon by ensuring prevention efforts, such as greater STI screening coverage and easier access to sexual health services, are sustained and that they continue to focus on high risk groups such as young people and men who have sex with men

Main trends

The latest data from GUM clinics suggest that, overall, the recent upward trend in new diagnoses of sexually transmitted infections (STIs) in the UK may be abating. The total number of new STI diagnoses reported by GUM clinics (including chlamydia, gonorrhoea, herpes, warts and syphilis) rose by only 0.5% last year (397,909 to 399,738), although "other STI diagnoses" (such as recurrent presentations) increased by 4% (257,890 to 268,109) over the same period (see figure 1). The modest rise in total numbers of new STI diagnoses between 2007 and 2008 was primarily associated with increased diagnoses of viral STIs. Over the same period, there was evidence that diagnoses of bacterial STIs either stabilised or declined.

Figure 1. Trends in diagnoses made in GUM clinics in the UK, 1999-2008*

* Cases diagnosed by GUM clinics are categorised as follows:
New STI diagnoses :
Chlamydial infection (uncomplicated and complicated); Gonorrhoea (uncomplicated and complicated) infectious and early latent syphilis; genital herpes simplex (first attack); genital warts (first attack); new HIV diagnosis; non-specific genital infection (uncomplicated and complicated); chancroid/lymphogranuloma venerum (LGV)/donovanosis; molluscum contagiosum; trichomoniasis; scabies; and pediculus pubis.
Other STI diagnoses :
Congenital and other acquired syphilis; Recurrent genital Herpes simplex; recurrent and re-registered genital warts; subsequent HIV presentations (including AIDS); ophthalmia neonatorum (chamydial or gonococcal); and epidemiological treatment of suspected STIs (syphilis, chlamydia, gonorrhoea, non-specific genital infection)
.

 

Main categories of STIs

Gonorrhoea and syphilis

The recent downward trend in gonorrhoea diagnoses continued in 2008, with overall numbers dropping by 11% in the last year (18,649 to 16,629) (figure 2). New diagnoses of gonorrhoea are now at their lowest level since 1999. This latest decrease was observed in women (5,811 to 5,516) and in men (12,838 to11,113) including men who have sex with men (MSM)( 3,765 to 3,316).

Figure 2. New diagnoses of gonorrhoea at GUM clinics in the UK, by gender and sexual orientation, 1999-2008: uncomplicated infection

Syphilis remains a relatively rare infection in the UK overall. A pronounced increase in total primary and secondary syphilis diagnoses was observed between the late 1990s and 2005 but since then numbers have been stable or have declined slightly (figure 3). This rise was primarily driven by increased transmission among MSM although transmission among heterosexuals also rose (figure 3) [1]. Between 2007 and 2008 numbers fell by 4% from 2,633 to 2,524 cases, with the decline seen in heterosexual men and women as well as MSM. Although numbers of diagnoses are relatively small in number, syphilis transmission in heterosexuals is of concern because it increases the likelihood of congenital syphilis.

Syphilis and gonorrhoea infections tend to be geographically clustered and concentrated in specific population 'core' groups, predominantly black ethnic minorities and MSM [2]. Effective local interventions may therefore have had a significant influence on transmission and frequency of these infections.

Figure 3. New diagnoses of syphilis at GUM clinics in the UK, by gender and sexual orientation, 1999-2008: primary and secondary syphilis

Genital chlamydial infection

Genital chlamydial infection remained the most commonly diagnosed STI in GUM clinics with 123,018 diagnoses in 2008, double the number of diagnoses made 10 years ago, and a 1% rise on the 121,791 diagnoses in GUM clinics in 2007. However, substantial and increasing numbers of chlamydia diagnoses are made outside the GUM clinic setting, in general practice, community contraceptive services, and in England, in a range of community healthcare and non healthcare-based settings as part of the National Chlamydia Screening Programme (NCSP). In 2008, the total number of chlamydia diagnoses reported in the UK, including those made outside the GUM clinic setting, was 200,959.

The rise in numbers of chlamydia diagnoses over the last 10 years has primarily been associated with greater coverage of chlamydia testing and the use of increasingly more sensitive diagnostic tests [2]. In 2008, 1.2 million sexual health screens (which include a test for chlamydia and gonorrhoea at minimum) were performed in UK GUM clinics, an increase of nearly 50% since 2004 (858,486 to 1,279,439). In England, between April 2008 and March 2009, the NCSP reported a further 1.1 million chlamydia tests in those aged 15 to 24 years done outside the GUM clinic setting [3]. Improved uptake of testing ensures prompt treatment of those infected, thereby reducing the risk of transmission and the development of complications.

Viral STIs

Between 2007 and 2008, numbers of diagnoses of first episode genital herpes increased by 10% (26,270 to 28,957) and those of recurrent herpes by 11% (18,265 to 20,361). The rise was seen in women and men, including MSM. Numbers of genital herpes diagnoses have been rising gradually for many years. However, recent rises have been particularly noteworthy and were probably due to much greater use of highly sensitive molecular tests [4]. The number of first episode genital warts diagnoses rose by 3% (89,515 to 92,525) and those of recurrent or re-registered case by 4% (67,376 to 69,935), between 2007 and 2008. For both genital herpes and warts, 97% of first episode diagnoses were reported among heterosexuals.

STIs in young people

Although young people aged 16 to 24 years represented only 12% of the population in 2008, they account for nearly half of STIs diagnosed in GUM clinics (figure 4) [5]. Young people experience higher rates of infection because they are more sexually active, more likely to partake in risky behaviours and may be more susceptible to infection [6,7,8]. In 2008, rates of chlamydia, genital warts and gonorrhoea diagnoses made in GUM clinics were highest in women aged 16 to 19 (1406, 850 and 135 per 100,000 population, respectively) and men aged 20 to 24 (1163, 816 and 152/100,000), while rates of genital herpes diagnoses were highest in women and men aged 20 to 24 (251 and 133/100,000).

Figure 4. Percentage of sexually transmitted infections diagnosed among young people (16-24), UK, 2008

Conclusions

Efforts to help control STIs, including the improved availability and uptake of sexual health screening in the UK, may be beginning to help slow transmission of bacterial STIs. However, numbers of STI diagnoses remain higher than they were 10 years ago. While much of this increase is associated with more testing and improved diagnostic sensitivity, it is clear that high rates of infection persist in some population groups. Recent modest improvements in sexual health should be built upon by ensuring prevention efforts, such as greater STI screening coverage and easier access to sexual health services, are sustained. These efforts need to continue to focus on high risk groups such as young people and MSM.

References

1. HPA. STI Annual Data Tables: data from genito-urinary medicine (GUM) clinics, 24 July 2009.

2. HPA. Testing Times - HIV and other Sexually Transmitted Infection in the United Kingdom 2007. The UK Collaborative Group for HIV and STI Surveillance. London, November 2007.

3. http://www.chlamydiascreening.nhs.uk/ps/data/data_tables.html.

4. HPA. Data from UK GUM clinics up to 2007 indicates continued increase in diagnoses of sexually transmitted infections. Health Protection Report [serial online] 2008; 2(29): HIV/STIs.

5. HPA. Sexually Transmitted Infection in Young People in the United Kingdom: 2008 report. The UK Collaborative Group for HIV and STI Surveillance. London, 2008.

6. Johnson AM et al. Sexual behaviour in Britain: partnerships, practices and HIV risk behaviours. Lancet 2001 358: 1834-42.

7.Wellings K et al. Sexual behaviour in Britain: early heterosexual experience. Lancet 2001 358:1843-50.

8. Kaestle CE et al. Young age at first sexual intercourse and sexually transmitted infections in adolescents and young adults. Am J Epidemiol 2005 161: 774-80.

Pandemic flu: UK situation at 23 July 2009

The latest HPA Weekly Pandemic Flu Update [1] notes the following developments as at 23 July:

  • GP consultation rates in England for individuals presenting with flu-like illness rose sharply compared with the previous week;
  • the under-fives and 5-14 year olds continued to be the age groups predominantly affected, with the over-65s continuing to show much lower rates.
  • the majority of cases continue to be mild. The number of confirmed deaths related to swine flu remained 26 in England as at 23 July; and
  • HPA estimated that there had been 100,000 new cases of swine flu during the previous week (within a possible range of 60,000 to 140,000).

GP consultation rates for flu-like illness continued to increase sharply in England. In the week-ending 19 July, the average consultation rate was 155 per 100,000 compared with 73.4 per 100,000 in the previous week. There was less variation between the reporting rates in the three defined reporting regions in England (North 126, Central 172 and South 155) than had previously been observed.

References

1. Weekly pandemic flu update (23 July 2009), (HPA press release of 24 July 2009). HPA website: National Press Releases.