CHAPTER 6 Significant trends in the incidence of the communicable diseases of public health importance in 2009
Infections continue to be a major public health problem in Scotland. Although significant progress has been made in reducing their impact, much remains to be done to further reduce disease and suffering. This chapter summarises significant trends in the incidence of the communicable diseases of public health importance in 2009.
Gastro-intestinal and foodborne infections
Campylobacter infection remains the most common of the more severe GI infections with 6,378 cases of Campylobacter infection being reported to HPS in 2009, an increase of 30.7% compared to the 4878 reports in 2008 (a rate of 123.4 per 100,000 compared to 96 per 100,000). The incidence of Campylobacter in Scotland peaked in 2000 and then declined every year until 2004. The increase in 2009 brings the level of reported cases to slightly below the peak of 2000. The rise was not the result of any identified outbreaks but rather a growth in the number of cases throughout the year, across Scotland. No obvious reason for this increase has been identified.
Norovirus ( NV) infection is the most common of the less severe GI infections in Scotland. During 2009, 231 general outbreaks of NV were reported to HPS, a decrease of 28.7% compared to 2008.
A total of 237 confirmed cases of E. coli O157 were reported to Health Protection Scotland during 2009. The rate of reports per 100,000 population for the whole of Scotland was 4.6 in 2009, compared to 4.7 in 2008. The continued importance of both foodborne and farm-related sources of infection (as highlighted by the E. coli O157 Task Force) was reinforced in 2009 by inquiries on foodborne outbreaks in both Scotland and Wales, and by outbreaks in England involving visitors to open farms. In addition to recently updated national guidance on the public health management of VTEC, advice was published on reducing risk amongst rural communities and visitors.
The rate of Salmonella infection substantially declined in 2009: 16.4 per 100,000 population (847 reports) compared to 20.2 per 100,000 population 2008. There was an increase in reports of Salmonella monophasic Group B (94 reports in 2009 compared to 37 in 2008). Much of this increase was due to a strain with an indistinguishable molecular pattern and was associated with contact with reptiles. Investigations traced the source of the infection to imported feeder mice.
Bloodborne virus and sexually transmitted infections
During 2009, 2,013 new cases of hepatitis C antibody-positivity were diagnosed. This figure compares with 1553 and 1725 for 2007 and 2008, respectively. Of the 2009 cases, 47% (939) are known to have injected drugs, representing 90% of those with a known risk factor. At the time of diagnosis, 25% (510) were aged 20-29 years, 37% (749) were aged 30-39 years, 25% (498) were aged 40-49 years, 8% (163) were aged 50-59 years and 3% (60) were aged over 60 years. This brings the total to 27,355 cases of hepatitis C antibody-positivity ever diagnosed as at 31 December 2009, of whom 14% are known to have died. Approximately one in 220 of Scotland's population had been diagnosed hepatitis C antibody-positive. It is estimated that the number of undiagnosed hepatitis C antibody-positive cases in Scotland still exceeds the number of diagnosed cases.
In 2009, NHSScotland laboratories reported positive HIV-antibody test results for 417 individuals not previously recorded as HIV-positive. Of the 417 recently reported HIV-positive individuals, 291 (70%) are male, and 286 (69%) are aged between 25 and 44 years. The probable route of transmission was men who have sex with men ( MSM) in 137 cases (including a small number who were also injecting drug users), heterosexual intercourse in 196 cases, and injecting drug use in 15 cases. Of the heterosexual cases, 109 probably acquired their infection abroad. For 60 cases, the transmission category is, as yet, undetermined. The cumulative total of known HIV-positive individuals in Scotland is now 6247, of whom 4521 (72%) are male and 1726 (28%) are female; 2445 (39%) of the 6247 total reports are presumed to have acquired their infection outwith Scotland. At least 26% are known to have died.
In 2009, 64 cases of AIDS were reported by clinicians, 30 of which were diagnosed in 2009 with 34 diagnosed in previous years. The cumulative number of AIDS cases is now 1552, of whom 1227 (79%) are male, while 999 (65%) are known to have died.
Healthcare associated infections
Numbers of cases of Staphylococcus aureus bacteraemia (blood poisoning) have been monitored in Scotland since 2001. In the last year there were 2046 cases of Staphylococcus aureus bacteraemia in NHS facilities in Scotland. A quarter of these were MRSA ( n=533) and the majority MSSA ( n=1513). A significant year on year reduction of 6.1% has been observed since 2005. MRSA bacteraemia has reduced year on year by 14.5% and MSSA by 1.7%. The majority of MRSA isolates (81%) typed by the Scottish MRSA reference laboratory, as part of the snapshot programme in the last year, were attributable to the epidemic strain EMRSA-15 and there have been substantial reductions in these infections since this time.
Multiple infection prevention and control interventions have been implemented since 2001. Some of these, such as the hand hygiene campaign, will have made a contribution to reducing HAI overall. The reduction in S. aureus bacteraemias may also result from NHS boards implementing special measures to reduce infections associated with peripheral vascular catheters ( PVC). Whilst inroads in reducing these infections have been made, nevertheless there continue to be significant numbers of cases. It is anticipated that wider implementation of these measures will lead to further reductions in S. aureus bacteraemias.
Clostridium difficile infection ( CDI) surveillance in NHSScotland identified 3625 cases in the last year in those over 65 years. The annual overall rate for Scotland in 2009 was 0.71 per 1000 total occupied bed days), which is a decrease of 42% compared to 2008. The significant decreases seen in Scotland have been mirrored in other parts of the UK.
C. difficile infection rates in this country are undoubtedly high, but it is difficult to get a clear picture of how this compares to other countries; even within the UK, there are substantial differences in surveillance case definitions.
The reduction of CDI rates is likely to be a result of a combination of improved infection control procedures (including improved hand-hygiene, environmental cleaning and adequate use of isolation rooms), implementation of antimicrobial stewardship, and improved education and communication at all levels within the service. This also includes implementation of over-arching strategic plans in NHS boards to reduce the burden of CDI. This list is not exhaustive.
The relative impact of each action is difficult to quantify because of concurrent implementation of a number of different strategies.
Rates for surgical site infection ( SSI) under mandatory national surveillance are low by comparison to CDI. Rates of infection in the hip arthroplasty and caesarean section surgery categories have significantly reduced since surveillance became mandatory in 2001. In total, the surveillance system detected 150 cases of SSI following hip arthroplasty surgery and 595 cases following caesarean section surgery in 2009. Half of all SSI following hip arthroplasty surgery were detected after discharge and on readmission to hospital. Continued implementation of the Scottish Patient Safety Programme controls for SSI over the next year should continue to contribute to reducing these clinically significant infections.
Vaccine preventable diseases
As measles has become rare in Scotland, it is difficult to diagnose clinically without laboratory tests. There were 172 notifications for measles in Scotland in 2009 and 17 were laboratory confirmed. This compares with 219 notifications and 54 laboratory confirmed cases in 2008. In every year, the majority of measles cases occur in unimmunised individuals.
The total number of mumps notifications and laboratory confirmed cases in 2009 was 1105 and 583 respectively compared with 720 mumps notifications and 172 laboratory confirmed cases in 2008. Cases continue to be mainly among the young adult age group (aged 15-24 years), who are often under immunised against mumps, not having been routinely offered two doses of MMR vaccine when they were children. There were 93 notifications of rubella in 2009, and no laboratory confirmed cases. This compares with 106 notifications and four laboratory confirmed cases in 2008. In 2009, uptake of one dose of MMR by 24 months was 93.6% and for those reaching 5 years of age, 96.1%, thus remaining above the target of 95% of children receiving at least one dose by the age of 5.
The total numbers of notifications and laboratory confirmed cases of pertussis in 2009 were 83 and 99 respectively, compared with 134 notifications and 88 laboratory confirmed cases of pertussis in 2008. Whooping cough is known to be under-notified in Scotland.
There have been no reported cases of meningococcal serogroup C infection since four cases were reported in 2007, indicating the effectiveness of the meningitis C vaccine campaign. A total of 139 cases of other types of meningococcal infection were reported to HPS in 2009 representing an annual incidence of 2.69 cases per 100,000 population. This compares with 125 cases reported in the same period of 2008 and 157 cases in 2007. Meningococcal disease occurred more frequently in younger age groups: 46.0% (64 cases) were aged less than 5 years.
Pneumococcal conjugate vaccine ( PCV-7) has been part of the routine childhood immunisation schedule since September 2006. The PCV-7 has now been replaced with a PCV-13 vaccine since late spring 2010. The new vaccine will follow the same three dose immunisation schedule at 2 and 4 months of age followed by a booster at 13 months. PCV-13 will protect against the same seven serotypes of Streptococcus pneumoniae as PCV-7 and 6 additional serotypes. Thirty nine cases of Invasive Pneumococcal Disease reported in 2009 were in children aged under 5 years. This compares with 34 cases in the same time period of 2008. Twenty-three cases were aged under 2 years and eligible for vaccination. The majority of these cases (16; 69.6%) were caused by serotypes not protected by PCV-7 but by PCV-13. There were 3 cases aged 5 years or under who were infected with a serotype of Streptococcus pneumoniae covered by PCV-7. One case was aged less than 2 months and not yet eligible for vaccination. The remaining two cases (aged 3-11 months and 2 years) had not received the full course of PCV-7 vaccine.
Vaccine uptake remains high in Scotland. As of December 2009, uptake rates by 24 months of age for completing primary courses of diphtheria, tetanus, pertussis, polio, Hib, MenC and PCV were between 96% and 98%. Uptake rates for the two booster vaccines Hib/MenC and PCV, given at 12 and 13 months, were at 93.9% and 94.1% respectively in children reaching 24 months of age. ( ISD 2009)
There were 503 notifications of tuberculosis during 2009. This was similar to 2008 when there were 502 notifications, but this figure represents a continued increasing trend since 2005 when there were 389 notifications. The last year in which a comparable notification figure was recorded was in 1996 when it was 509.
This increase in notifications of tuberculosis is mirrored by an increase in reports to the Enhanced Surveillance of Mycobacterial Infections ( ESMI) system. During 2009, the ESMI scheme provisionally reported 468 cases of tuberculosis (compared with 455 cases reported in 2008) which is the highest ever number reported to the ESMI scheme since it began in 2000.
Analysis of the 2008 ESMI data reveals that the incidence in Scotland of 8.8 cases per 100,000 population remains within the WHO target of less than 10 cases per 100,000 and is less than the rest of the UK (15.5 cases per 100,000 reported in England and 14.1 cases per 100,000 for the whole of the UK in 2008). ( HPA 2009)
There has been a steady increase in the proportion of non- UK born cases since enhanced surveillance began in 2000. In total, 49.0% of cases reported to ESMI in 2008 were born outwith the UK. The most common age group in the UK born cases was 55-64 years (35; 17.9%) compared to 25-34 years (90; 42.5%) in the non- UK born. In 2008 risk factors for the disease were identified for 96 (24.5%) cases. The most common was alcohol misuse
(52 cases), being a refugee (34 cases), immunosuppression (32 cases), working in healthcare (15 cases), homelessness (12 cases), residency in a residential or corrective institution (six cases) and drug misuse (five cases).
Infectious diseases still pose a considerable threat with significant numbers of people having to attend their GP or being admitted to hospital as an emergency. 2009 has seen welcome reductions in levels of infection especially healthcare associated infections and vaccine preventable diseases. The number of new cases of tuberculosis, HIV, hepatitis C and campylobacter infection demonstrates the continuing need for action on the underlying reasons as to why people are falling ill with these conditions and on the prevention of onward transmission of infection from them.