Scale of the HCAI Problem-Prevalence and Incidence

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Chapter: Pharmaceutical Microbiology : Public Health Microbiology: Infection Prevention And Control

An assessment of the number of cases of HCAI and the risk of infection for different patient groups is based on a series of different measurements. Point prevalence studies have been undertaken in many countries to give a snapshot of the number, and the percentage, of patients with any type of HCAI in a particular healthcare setting on a specific day.



An assessment of the number of cases of HCAI and the risk of infection for different patient groups is based on a series of different measurements. Point prevalence studies have been undertaken in many countries to give a snapshot of the number, and the percentage, of patients with any type of HCAI in a particular healthcare setting on a specific day. Prevalence studies in various developed countries over the last decade have shown overall prevalence rates between 5% and 10% (Table 16.1). A prevalence study in the four UK countries and the Republic of Ireland in 2006 showed an overall prevalence of 7.6%, ranging from 4.9% in the Republic of Ireland to 8.2% in England. The low rates in the Republic of Ireland probably reflected a rather younger patient population overall and the higher number in England was linked almost entirely to much higher numbers of cases of CDI (2006 was the height of the epidemic of CDI in hospitals in England). The commonest types of infection were urinary tract infection, followed by skin and soft tissue infections and wound infections, respiratory infections, and gastro-intestinal infections (Table 16.2). Bloodstream infections accounted for only 7% of HCAIs but represent the most severe end of the spectrum of disease. MRSA infections of all types accounted for 16% of the HCAIs and CDI was 17% of the total in hospitals in England but only 5% in Wales, Northern Ireland and the Republic of Ireland.


Prevalence studies provide valuable comparisons between hospitals and countries and show the general contribution of the various types of HCAI. However, they do not represent the actual number of cases of different HCAIs over time, i.e. the incidence of infection in different hospitals, wards or patient groups. For example, a point prevalence of 8.2% does not mean that 8.2% of the patients admitted to the hospitals in England developed an HCAI because the infected patients tend to be more seriously ill and have longer stays in hospital both from their underlying illness and as a result of their HCAI; therefore, the incidence is always less than the point prevalence. Incidence is measured by ongoing and continued surveillance of specific infections in which all cases of the infection are recorded and related to the number of patients at risk. The HCAIs that are most commonly subject to surveillance programmes are bacteraemias (bloodstream infections) caused by specific healthcare-associated pathogens such as MRSA or ESBL-producing E. coli (because they represent the most severe types of HCAI), SSIs (one of the key indicators of the quality of a surgical service or an individual surgeon), and CDI. Surveillance data are necessary for monitoring infection prevention and control activities at national and regional level, which can provide useful comparisons between hospitals for patients who may choose where they wish to have their treatment. However, surveillance with timely feedback and data is particularly important at local level, within individual hospitals to ensure delivery of a high quality of care. Most surveillance programmes have depended on voluntary reporting of the infections to regional or national programmes but in several countries some high-profilveillance programmes have been made mandatory to ensure that infection prevention and control is made a high priority for health service managers and clinicians alike. Mandatory surveillance of MRSA bacteraemia was introduced in England in 2001, followed CDI, glycopeptide-resistant enterococcal bacteraemia and SSIs in orthopaedic surgery in 2004. Similar approaches have been applied in other UK countries, the Republic of Ireland, European countries and the USA (mostly at an individual state level).

A further development of basic surveillance (i.e. reporting numbers of cases) is the application of enhanced surveillance in which information about patient demographics, risk factors, and outcomes is included. This can then be linked to root cause analysis of individual cases to provide valuable information about target areas for preventive measures.


What Has Surveillance Told Us?


Mandatory surveillance of MRSA bacteraemia in England showed a steady rise in cases to a peak of 7700 in 2004. Public and political concern about MRSA resulted in the government setting a target for a 50% reduction in MRSA bacteraemia over the 3 years 2005–2008. The surveillance data enabled active performance management through all levels of the (national) health service, provided pressures for improved infection prevention and control actions, and showed show the target was being achieved. Information from enhanced surveillance within this programme showed the importance of patients’ ages and underlying conditions as particular risk factors, and most significantly showed the importance of intravenous catheters and cannulae, renal dialysis catheters, urinary catheters and chronic wounds and ulcers as sites of MRSA infection leading to bacteraemia.


A similar approach was taken with CDI when mandatory surveillance showed that there were 55 000 cases in patients over 65 years of age in England in 2006; as these represent about 75% of cases, this means that there were around 70 000 cases overall. Guidance on prevention and control measures (based on the 1994 guidance) and a target to reduce the number of cases by 30% by 2011 focused activities in NHS hospitals and the 30% reduction was achieved within the first year (2008–2009).


SSI surveillance in orthopaedic surgery has been a national requirement in all UK countries for several years. This is a type of surgery with relatively low rates of infection (<5%) but surveillance has focused attention on infective complications, shown differences between surgical procedures, and also shown a steady improvement in rates in all the countries. However, the very short length of stay now usual for patients after these operations means that some infections only manifest themselves when the patient is at home. This has shown the need for including some system of post discharge surveillance for surgical site infection to give a realistic picture of these HCAIs. This approach is being pioneered in the UK and the Republic of Ireland in relation to infections following caesarean section births where there is a clear opportunity for professional input to post-discharge surveillance because the mothers are seen at home by a midwife or health visitor.


The HCAI Challenge


The surveillance programmes in various countries have shown the scale of the challenge set by HCAI in modern health and social care services. Why has this situation developed? There is a strong argument that during the last quarter of the 20th century, infections (including HCAI) had not been regarded as an important part of modern medical practice. There had been a view from the late 1960s onwards that infectious diseases had been conquered and that antibiotics and vaccines provided the answer. The importance of infection prevention and control measures was not given its former position in clinical training of doctors and nurses. Modern medicine was making tremendous progress in the treatment of malignant diseases, cardiovascular disease, transplantation, and chemotherapy, and in the management of chronic diseases. Life expectancy increased markedly and the proportion of very elderly people in the population, with their inevitable healthcare needs, rose rapidly. This created a vulnerable patient population at high risk of infection, but these infections were regarded as incidental nuisances rather than the major risk to a patients’ health and potential mortality which they are. Infections were regarded as the province of the infection specialists (medical microbiologists, infection control nurses) who had plenty of interesting work to do but a generally low profile. The situation changed with the advent of the 21st century and the recognition of the human and financial costs of HCAIs in a modern healthcare service.


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