Eurosurveillance - Volume 11, Issue 11, 01 November 2006

This issue of Eurosurveillance includes a report by Georgia Spala et al of the investigation of a suspected outbreak in Greece of avian influenza (A/H5N1 virus infection) in humans [1]. This took place in the early spring of 2006 when infected wild birds appeared in many European Union (EU) countries. There were confirmed infections in birds in Greece, but after careful investigation, no human infections were found. However, the massive investigation and control that had to take place around the infections and deaths in the outbreak in Turkey in December 2005 and January 2006 [2] is a reminder of what could have been in Greece or other EU countries.

Surveillance systems have been described as the nerve cells of public health with afferent arms receiving information, cell bodies analysing the information and efferent arms initiating appropriate action or further distribution of information [1]. Increasing numbers of scientific publications on the methodology and evaluation of surveillance systems seem to underline the importance of surveillance systems in public health. The most often cited references in these publications appear to be the definition of public health surveillance by Thacker and Berkelman [2] and variations thereof, and the recommendations for evaluating surveillance systems from 1988 [3] and its update from 2002 written by working groups at the Centers for Disease Control and Prevention (CDC) in the United States[4].

The recent wide geographic spread of the highly pathogenic avian influenza A/H5N1 virus has important public health implications. Several wild migratory birds were confirmed to be infected with avian influenza A/H5N1 in Greece in February and March 2006. The aim of this paper is to report data from potential H5N1 human cases that presented to local hospitals during this period with a respiratory infection and expressing concern about exposure to avian influenza. A case-control investigation was conducted that included case identification with the use of a structured definition, review of epidemiological and clinical characteristics and molecular testing for avian influenza A/H5N1. The setting was the entire country of Greece during February and March 2006. The main outcomes were rates of possible cases (meeting both a clinical and an epidemiological criterion) and clinical or epidemiological characteristics differentiating them from potential cases that met either one of the criteria of a possible case, but not both. Twenty six potential patients (81% of whom met a clinical criterion, and 39% of whom met an epidemiological criterion) presented and most (85%) were admitted in local hospitals during the period of interest. The majority of cases (85%) were observed in northern Greece where most of the confirmed A/H5N1 avian cases were documented. Five of the 26 evaluated patients met the definition of a possible case. These clustered within the early period of confirmed A/H5N1 cases in wild migratory birds (P=0.05). Molecular testing was negative for all possible cases. Application of a revised case definition constructed according to newer European Union guidance resulted in the exclusion of two possible cases. Several potential A/H5N1 human cases were recently identified in Greece. Both the timing of identification and the geographical location of potential cases suggest an increased awareness on the part of the general public, as well as poor interpretation of the case definition by the clinicians.

Surveillance systems for infectious diseases build the basis for effective public health measures in the prevention and control of infectious diseases. Assessing and improving the quality of such national surveillance systems is a challenge, as many different administrations and professions contribute to a complex system in which sensitive information must be exchanged in a reliable and timely fashion. We conducted a multidisciplinary quality circle on the national public health surveillance system in Germany which included clinicians, laboratory physicians, and staff from local and state health departments as well as from the Robert Koch-Institut. The recommendations resulting from the quality circle included proposals to change the federal law for the control of infectious diseases as well as practical activities such as the change of notification forms and the mailing of faxed information letters to clinicians. A number of recommendations have since been implemented, and some have resulted in measurable improvements. This demonstrates that the applied method of quality circle is a useful tool to improve the quality of national public health surveillance systems.

Between August 2005 and March 2006 in France, 69 cases of Salmonella enterica serotype Manhattan (Salmonella Manhattan) were reported, 51 (74%) of them from southeastern France. At the time of the alert (November 2005), 13 cases and 33 controls were interviewed. Cases were more likely than controls to have eaten pork sausages (OR=5.9, confidence interval CI [1.3; 26.9]) and beef (OR=9.3, CI [1.3; 68.6]). At the same time, 19 strains of Salmonella Manhattan isolated from meat products in southeastern France, reported to the French food safety agency (Afssa, Agence française de sécurité sanitaire des aliments) in September and November 2005, had an indistinguishable PFGE profile to the 7 human isolates of Salmonella Manhattan from the outbreak in southeastern France. Trace-back investigations revealed that pork samples came from one wholesaler whose pork products had tested positive for S. Manhattan during routine food testing in August 2005. This wholesaler supplied retail outlets in southeastern France. Additionally, a slaughterhouse supplying the wholesaler was inspected and widespread contamination with Salmonella spp. and S. Manhattan was found. Cooperation between the national agencies in charge of human health (Institut de veille sanitaire, InVS) and food safety (Afssa) allowed us to determine the most probable source of contamination and to take appropriate control measures.

During the summer of 2005, four cases of active tuberculosis from the same occupational setting were investigated in Manchester, UK. The index case had been diagnosed in December of the previous year. At that stage the closest occupational contacts had been screened, all of whom were assessed as being free from active disease, and none had met nationally recommended criteria for chemoprophylaxis for latent tuberculosis infection (LTBI). In June 2005, two work contacts developed progressive primary extrapulmonary (pleural) TB. Following a detailed risk assessment, the screening programme was widened to include 137 staff who worked at the job centre (employment agency) where the first four cases had been found. This screening programme was based on tuberculin Mantoux testing, CXR and gamma-interferon testing. Of these 137 contacts screened, one additional person was found to have active disease and six others were offered chemoprophylaxis for LTBI. The isolates from the index case and the first two secondary cases were indistinguishable on VNTR-MIRU (variable number tandem repeat - mycobacterial interspersed repetitive unit) typing at 15 loci. No samples were available for testing from the fourth case of active disease. Management of this incident has benefited from the evolving fields of both genotyping and diagnostic testing for LTBI. However, further research into the epidemiological inferences made through genotyping, as well as the significance of a positive gamma-interferon test in assessing the risk of development of active disease, is still required.

Letter to the Editor