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Volume 4 No 11; 19 March 2010

World TB day and UK surveillance update


World TB day on 24 March marks the anniversary of the day, in 1882, that Dr Robert Koch identified the tuberculosis (TB) bacillus as the causative agent of tuberculosis. This year the theme is “on the move against tuberculosis” which focuses on innovative and novel strategies to stop TB.

The year 2010 marks the halfway point of the Global Plan to Stop TB (2006-2015) [1]. Estimates of the World Health Organization (WHO) published in March 2009 indicate that, in 2008, there were 9.4 million new cases worldwide (139 per 100,000) and 1.3 million deaths due to TB [2].  Seven out of nine WHO-defined epidemiological sub-regions have achieved the goal to reverse the trend of increasing incidence ahead of the target year 2015, and in four regions prevalence and mortality have also halved since 1990. However, it is unlikely that the target level for prevalence and mortality will be achieved on a global scale. In particular, drug resistant tuberculosis strains present a major challenge to the global effort to control TB, as outlined in a recent WHO report [3]. In 2008, it was estimated that 440 000 people had multi-drug resistant (MDR) TB, with 50% of cases thought to occur in China and India. In the 46 countries that test for resistance to second line drugs, extensively drug resistant TB (XDR TB) was found in 5.4% of MDR TB cases.

The HPA has released a newsletter to coincide with world TB day [4] which provides a UK TB surveillance update and outlines fresh approaches to control TB in the UK. New initiatives include the launch of the National Strain Typing Service, the trialling of an opt-out system for HIV testing in TB clinics in London and new methods for raising awareness and for TB case management.

Provisional data on the number of TB cases in the UK shows that 9153 cases were reported to enhanced national surveillance in 2009; a rate of 14.9 per 100,000 and a 5.5% increase compared to the provisional figures from 2008. This is mainly due to increased case numbers reported in eight out of nine regions in England (see figure). A consistent rise in incidence has been observed over the last decade and it is now crucial that efforts are consolidated nationally to halt and ultimately reverse this trend. Provisional data are still subject to change due to de-notifications, de-duplication of records and late notifications of TB. Finalised 2009 data will be published by HPA later this year.

Provisional number of TB cases reported by region/country: UK, 2005-2009


References

1. The Global Pan to Stop TB 2006-2015: progress report 2006-2008. World Health Organization: Geneva. 2009.

2. Global tuberculosis control: a short update to the 2009 report. World Health Organization: Geneva. 2009.

3. Multidrug and extensively drug-resistant tuberculosis: 2010 Global Report on Surveillance and Response, World Health Organization: Geneva. March 2010 [PDF 852 KB].

4. HPA Centre for Infections. Tuberculosis update. London: HPA, March 2010.

Acknowledgement
The HPA would like to acknowledge the contribution of colleagues in the Local and Regional Services network, Health Protection Scotland, the National Public Service for Wales and the Communicable Disease Surveillance Centre Northern Ireland in providing the data for this report.

Trends in mandatory surveillance data for MRSA bacteraemia and C. difficile infection (data for England, October 2007 to December 2009)

The HPA has published its second quarterly epidemiological commentary reporting analyses of data generated by the mandatory surveillance of meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia and Clostridium difficile infections (CDI) occurring in NHS acute trust hospitals in England [1,2].

The commentary – of which this article is a summary – describes trends in the mandatory reports of these infections over a period of nine quarters – from October 2007 to December 2009 – aggregated over all English NHS acute trusts. The full epidemiological commentary is available on the HPA website [3] and provides further information about the age and sex profiles of patients with these infections and the patterns in patient provenance. The commentary also includes two special feature articles: the first introduces preliminary trend analyses from 2006 to 2009 in the presumed cause of MRSA bacteraemia, based on voluntarily reported data; the second is a preliminary analysis of the subset of patients who have had more than one episode of C. difficile in 180 day follow up period.

MRSA bacteraemia

Total counts of MRSA bacteraemia during the previous nine quarters are shown in figure 1, divided into two categories: trust-apportioned episodes (this category includes patients presumed to have been infected while admitted to the trust*), and non trust-apportioned episodes (‘all other episodes’).

The purpose of apportioning episodes either to acute trust or all other sources is to explore the changing epidemiology of the infection in the healthcare setting. By distinguishing between trust apportioned and all other episodes, we can conduct a more refined analysis of the disease in the relevant settings.

Figure 1. Counts of trust-apportioned and all other episodes of MRSA bacteraemia (October – December 2007 to October – December 2009)


Overall, there has been a 59% decrease in the number of episodes reported during this surveillance period in England, from 1,092 cases in October-December 2007 to 444 cases in October-December 2009. Among trust-apportioned episodes, there has been a 64% decrease during this surveillance period, from 654 episodes to 237 episodes. In comparison with the previous quarter (July-September 2009) there has been no significant change (236 episodes in July-September 2009 vs. 237 episodes in October-December 2009). The number of all other episodes has decreased 53% from 438 episodes in October-December 2007 to 207 episodes in October-December 2009. There has also been an 8% decrease since the previous quarter (July-September 2009), when 226 episodes were reported as compared with the 207 episodes reported for October-December 2009.

Clostridium difficile infection

In the most recent quarter, October-December 2009, the total number of reports of CDI was 6,009. After apportioning cases†, the counts were similar for the categories of trust apportioned (3,027; 50.4%) and all other episodes (2,982; 49.6%). Between October-December 2007 and October-December 2009 there has been a 58% decrease in the counts of trust-apportioned episodes from 7,157 to 3,027 and a 41% decrease in the number apportioned as all other episodes from 5,091 to 2,982 (Figure 2).

The rate of decline in trust apportioned counts has slowed between October-December 2008 and October-December 2009, compared with the decline between the same quarters in the previous year. Between October-December 2008 and October-December 2009 the number of cases fell by 30% (4,310 to 3,027) compared to 40% (7,157 to 4,310) between October-December 2007 and October-December 2008. The difference between the two years could be due to the immediate impact of interventions on reducing the numbers of infections, but with the rate of decline slowing it may be that with the continued use of those infection control protocols, the more ‘easily’ preventable infections occur less frequently. Comparing between the last and current quarters, between July-September 2009 and October-December 2009 the number of cases decreased by 2% (3,098 to 3,027); over the same period in 2008 they decreased by 8% (4,687 to 4,310).

The number of cases apportioned as ‘all other episodes’ reduced by 29% (5,091 to 3,597) between October-December 2007 and October-December 2008; between October-December 2008 and October-December 2009 the rate of decline was 17% (3,597 to 2,982). Between July-September 2008 and October-December 2008 there was a 16% reduction (4,261to 3,597) in the number of cases. By comparison there has been a 10% reduction (3,320 to 2,982) over the same quarters in 2009. The convergence of the lines of counts of trust apportioned and all other episodes is curious. It will be interesting to see over the next few quarters whether the rate of decline between quarters is similar in the two arms of the apportioning process.


Figure 2. Counts of trust-apportioned and all other episodes of CDI, October – December 2007 to October – December 2009


Notes

* MRSA bacteraemia trust-apportioned episodes : The analysis of trust apportioned and all other reports is based on the model outlined by the National Quality Board. This includes patients who are (i) in-patients, day-patients, emergency assessment patients; AND (ii) have had a specimen taken at an acute trust; AND (iii) specimen is 2 or more days after date of admission (admission date is considered day ‘0').

† CDI trust-apportioned episodes : include patients who are (i) in-patients, day-patients, emergency assessment patients; AND (ii) have had a specimen taken at an acute trust; AND (iii) specimen is 3 or more days after date of admission (admission date is considered day ‘0').

The next quarterly commentary (covering January 2008 to March 2010) will be published on 18 June 2010.

References

1. Mandatory Clostridium difficile infection surveillance scheme. HPA website: Infectiousdiseases › Infections A-Z › Clostridium difficile › Epidemiological data › Clostridium difficile Mandatory Surveillance.

2. Mandatory Staphylococcus aureus bacteraemia surveillance scheme. HPA website: Infectiousdiseases › Infections A-Z › Staphylococcus aureus › Epidemiological Data › Mandatory Staphylococcus aureus bacteraemia surveillance scheme.

3. "Quarterly epidemiological commentary: trends in MRSA bacteraemia and C. difficile infection from October 2007 to December 2009", March 2010 (PDF, 890 KB). HPA website: Infections A-Z › Staphylococcus aureus › Epidemiological Data › Mandatory Staphylococcus aureus bacteraemia surveillance scheme › Quarterly Epidemiological Commentaries.

Further rise in HIV diagnoses of infections acquired heterosexually within the UK: 2009 data


In 2009, an estimated 6,900 persons were newly diagnosed with HIV in the United Kingdom after adjusting the observed number of 5,963 diagnoses for reporting delay. Following a steep increase in the annual number of diagnoses between 1999 (3,249) and 2005 (7,988), the 2009 data shows an overall year on year decrease since 2005. Having adjusted for undetermined risk, over a half of the people newly diagnosed in 2009 (55%; 3780) probably acquired their infection through heterosexual contact and 41% (2800) through sex between men.

The overall decline in annual diagnoses masks the further rise in number of new diagnoses among those probably infected heterosexually within the UK with an estimated 1,220 new diagnoses in 2009, up from 1,080 the previous year. Of the estimated 1,220 persons infected heterosexually in the UK, 45% were of white ethnicity and 39% of black African ethnicity.

The number of new diagnoses among persons probably infected heterosexually abroad has fallen from an estimated peak of 4,260 in 2004 to 2,560 in 2009 (see figure). While the majority of persons infected heterosexually continue to acquire their infection abroad, mostly in sub-Saharan Africa, the proportion that do so has declined from 88% in 2003 to 68% in 2009.

Although numbers remain high, the trend in new diagnoses in men who have sex with men (MSM) is flat (figure), with the estimated 2,800 new diagnoses in 2009 being similar to annual numbers since 2005. Among HIV-infected MSM newly diagnosed in 2009, 83% probably acquired their infection within the UK and 85% were of white ethnicity. Sex between men remains the main route of HIV transmission within the UK.

Low numbers of estimated new diagnoses were made in 2009 in injecting drug users (160) and other exposure categories (160) such as mother to child transmission and recipients of blood and blood products.

Annual trend in HIV diagnoses by exposure category for the UK



Pandemic (H1N1) 2009 influenza vaccine for travel use


The Chief Medical Officer for England has written to all general practitioners to confirm that pandemic H1N1 (2009) influenza vaccine can be provided for the protection of travellers to southern hemisphere countries during their forthcoming influenza season [1,2].

References

1. Department of Health Central Alerting System. Pandemic H1N1 (2009) swine flu vaccine for travel use, 18 March 2010.

2. "Swine ‘Flu vaccine available for the protection of travellers", Department of Health press release, 19 March.