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18 November 2003

Travel health: Sentinel surveillance of imported infections: a worldwide issue

Introduction

Since 1998 the Scottish Centre for Infection & Environmental Health (SCIEH) has collaborated with clinicians in the collection, collation and analysis of travel-related infections/incidents diagnosed and treated in infectious disease units in Scotland (Sentinel Surveillance of Travel-Related Infections). This surveillance system was designed to quantify the infection/incidents, regions of risk and to estimate the burden of acute imported infections on the NHS. As dramatic changes in the incidence of emerging and new infections have occurred in recent years, the most notable of which is SARS, the sentinel surveillance is clearly in need of redesign. Here we summarise the progress so far of designing a new system that will take its place as part of an international collaboration aimed at estimating the burden of travel-related infections worldwide and rapidly identifying foci of emerging infections for pre-emptive or rapid reaction by the relevant authorities.

Travel related illness

It has been estimated that about 58,000,000 visits abroad from the UK occurred in 2001, three times the number in 19811. Approximately 5,000,000 (8%) of these were visits to Asia, Africa and South and Central America, representing a small fraction of worldwide travel from developed to developing nations. In Scotland specialised travel clinics exist providing advice and prophylaxis to enable the traveller of decreasing their risk of being infected, in addition to travel-related primary care and vaccinations based in general practice. However, large numbers of travellers to developing countries still return to the UK having had diarrhoea and/or respiratory symptoms while travelling abroad (Table 1)2.

Travellers returning to Scotland or entering for the first time may have infections due to organisms for which their immune systems are little prepared. Infections, such as falciparum malaria and schistosomiasis, can cause serious long-term problems, even death, if not treated immediately and adequately. In the context of risk to the overall health of the population of Scotland some cannot be transmitted within Scotland, due to a variety of ecological reasons, and therefore present no risk to the general public. However, a large proportion of travellers returning with respiratory, food-borne and blood-borne infections have the potential to transmit these within the Scottish population.

Surveillance of travel-related infections

In order to reduce the threat of such an occurrence two things must happen; 1) the rapid identification, diagnosis and treatment/isolation in port health authorities, general practices and the hospital setting, to reduce any threat posed by infected individuals and 2) the identification of current and new potential threats to travellers while they are abroad, to allow targeting of resources and to inform travellers so that they may take appropriate precautions.

Sentinel surveillance of infections diagnosed in infection diseases units in Scotland allows an estimate of the scale of the problem of the more serious imported infections. However, the pooling of such data with international partners increases the ability to identify new foci. To promote this, GeoSentinel was devised as a collaborative venture between the Centers for Disease Control and Prevention (CDC) and the International Society for Travel Medicine (ISTM). This network comprises 27 sites participating in full sentinel surveillance, located in the US, Canada, Europe, Asia, Africa, and Australia, as well as an additional 100 ISTM clinics communicating unusual cases and enhanced surveillance data. Alerts and advisories on important disease risks and outbreaks in collaboration with CDC and other international organizations are channelled through ISTM clinics for dissemination. This has resulted in the collation of 6,000 patient records/yr allowing the monitoring of trends in emerging infectious diseases, as well as a Rapid Worldwide Query-Response Capability identifying travel-related cases/outbreaks.

The mainstay in improving sentinel surveillance of travel-related infections in Scotland has been the desire to link into the GeoSentinel network while designing a surveillance tool that is pertinent for the Scottish population. A new surveillance form has been designed, based on GeoSentinel, which has been piloted in the Brownlee ID Clinic, Glasgow. This tool will allow the surveillance of imported infections at local, national and (via GeoSentinel) international levels. It will also allow SCIEH to access GeoSentinel data, increasing our awareness of outbreaks of new/emerging diseases at the international level allowing dissemination of important information to clinicians and travellers.

The target date for initiating the new sentinel surveillance is January 2004. Initially this data will be collected in Glasgow, with the aim of expanding the project to other infection diseases unit clinics in Scotland. A presentation will be made in December 2003 to the Scottish Infection Standards and Strategy Group on this new form in order to increase awareness and interest (see Current note 37/4604).

Future plans

While the new surveillance tool is being designed for use in clinical infection units, it must be noted that these see only a small proportion of all travel related infections in Scotland; usually more serious acute cases. It is hoped that surveillance may expanded to spotter general practices and port health authorities in order to increase our ability to monitor for the importation of infections as well as further contribute to knowledge of emerging infections at the international level.

Acknowledgments

We would like to thank the many ID consultants who supply data to SCIEH, SCIEH staff who collate the data as well as GeoSentinel staff (CDC, Atlanta) for fruitful discussions.

References

1. National Statistics. Travel Trends (Office for National Statistics, London, 2002) http://www.statistics.gov.uk/downloads/theme_transport/TTRENDS02.pdf

2. Redman, C.A., MacLennan, A., Wilson, E. and Walker, E. Adverse events among travellers to Asia, Africa and South & Central America from Scotland. Presentation submitted for the Africa-European Conference on Travel Medicine, 2004

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Author(s): Redman CA, Walker E Vol: 37 No: 46 Year: 2003 Page:

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