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Eurosurveillance, Volume 8, Issue 9, 01 September 2003
Surveillance report
Infectious diseases in Rome during the Millennium Year

Citation style for this article: Giorgi Rossi P, Sangalli M, Faustini A, Forastiere F, Perucci CA. Infectious diseases in Rome during the Millennium Year. Euro Surveill. 2003;8(9):pii=425. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=425

 

Giorgi Rossi P.1, M. Sangalli2, A. Faustini2, F. Forastiere2, C. A. Perucci2

1. Agency for Public Health, Rome, Italy
2. Department of Epidemiology, ASL (Local Health Unit), Rome, Italy

 


During 2000, the millennium year, 26 million people visited Rome. An improved surveillance system for infectious diseases, especially for foodborne disease outbreaks (FBDO), meningitis, and legionnaires' disease was introduced in 1997. This rapid alert network links public health services with the principal sources of diagnosis and laboratory based surveillance. For travel related legionnaires' disease, international surveillance was implemented. Specific control measures for FBDOs were adopted. No increase in the overall incidence of these diseases was observed, and no atypical pathogens in FBDOs or meningitis were isolated in 2000 relating to 1998-99. Cases of legionnaires' disease and FBDOs involving foreign tourists increased (10/4 and 7/2 observed/expected respectively). Three out of six FBDOs involving pilgrims occurred in religious guesthouses. While an increase in cases of legionnaires' disease and FBDOs among foreign tourists was observed by the surveillance system, the millennium year did not influence the epidemiology of infectious diseases in the residential population of Lazio.

Introduction
The millennium year 2000 brought 26 million visitors to Rome. The pilgrims as a group were characterised by heterogeneous geographic origin (16.1 million from Italy, 5.3 from western Europe, 1.5 from eastern Europe, 0.9 from Asia, 0.7 from North America, 0.6 from South America, 0.1 each from Africa and Oceania), short duration of stay (2.5 days), and congregation in large crowds.
Mass gatherings are considered high risk for the spread of infectious diseases (1-3). The surveillance of infectious diseases in the Lazio region was enhanced through a laboratory based system with special attention to diseases with high epidemic potential, high incidence, and short incubation period, ie foodborne disease outbreaks (FBDO), and meningitis. The European surveillance of legionnaires' disease provides information on diseases diagnosed abroad. A rapid alert network was implemented from hospital emergency departments (ED) and a group of general practitioners committed to treating pilgrims. This paper reports the results of the surveillance of these infectious diseases during the millennium year.

Methods
Since 1997, an integrated surveillance system involving statutory notification and the reporting of positive laboratory tests has been functioning in the Lazio region for the following pathogens: Salmonella, Campylobacter, pathogenic Escherichia coli, Giardia, Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, and Legionella pneumophila. For legionnaires' disease, an additional surveillance has been active since 1997, in accordance with the protocol of the European Working Group for Legionella Infections (EWGLI) (5). The principal sources of notifications, ie hospitals, general practitioners, emergency wards, and laboratories, participate in a rapid alert network for meningitidis and report probable cases of targeted diseases and suspected outbreaks to local public health services. Notification takes place immediately after diagnosis of suspected meningitis or FBDO and within 48 hours of suspected legionnaires' disease.

In 1997 guidelines for epidemiological investigation during FBDOs were introduced (6). A programme to control FBDOs was adopted during the millennium year, involving the Millennium Food Safety Committee. It included courses for public health workers about Hazard Analysis Critical Control Points (HACCP) as applied to catering for large gatherings and about epidemiological methods of conducting FBDO investigations. During World Youth Day (WYD), the most important gathering with more than 1.5 million pilgrims, there was only one food provider and processes for meal production had previously been agreed upon by the provider and the Millennium Food Safety Committee. Pamphlets with recommendations about safe food consumption and individual diarrhoea management were given to pilgrims during WYD.
We used the case definitions recommended by the Centers for Disease Control and Prevention (CDC) for the targeted diseases (7). Foreign tourists are defined as persons without Italian citizenship and not residing in Lazio (5.3 million inhabitants). During FBDO investigations, pilgrims were defined as groups coming to Rome for the millennium from any country. We compared the number of cases that occurred in 2000 (observed) with the mean number of cases in 1998 and 1999 (expected) (O/E). We considered the day of onset of symptoms as the date of incidence of the disease. We analysed in detail the three months with the most important gatherings: January (Epiphany, 6 January), April (Easter, 23 April), and August (WYD, 14-20 August). We calculated 95% confidence intervals (CI) of observed/expected ratios, assuming that both followed a Poisson distribution. For the differences between mean ill persons per FBDO, a t-distribution was used. We analysed the monthly frequency of visits to emergency departments (EDs) for foreign tourists and residents separately.

Results
There was an increasing trend in the number of cases and outbreaks of these infectious diseases from 1995 to 1999 (Figure).


The number of FBDOs and of cases of bacterial/viral meningitis and legionnaires' disease observed in the Lazio region did not increase in 2000 as had been expected based on the figures for 1998-1999 (Table). The FBDOs involving foreign tourists increased (O/E=3.5; 95% CI [0.9-16.3]). Cases of legionnaires' disease among foreign tourists exposed in Lazio showed an increase in 2000 (O/E=2.5; 95% CI [0.9-7.3]). The monthly average number of visits for foreign tourists to EDs for abdominal pain and intoxication was 167 with a peak (+75.9%) in August, while for residents it was 8860 visits with a smaller increase (+18.2%) the same month. A similar distribution of visits was reported for all causes of residents (161 700 visits/month, +12.0% in August) and foreign tourists (2755 vistits/month, +90% in August). A similar distribution of visits was reported for the accesses for all causes of residents (161 700 visits/month, +12.0% in August) and foreign tourists (2755 visits/month, +90% in August). The number of cases of these infectious diseases reported in January, April and August 2000 is similar to the number reported in the same months over the reference period, except for a peak of viral meningitis in August 2000 (O/E=2.0; 95%CI [0.9-4.5]). The mean number of ill persons per FBDO is larger in 2000 (difference 5.3; 95%CI [2.1-12.7]), due to a few large events. During the millennium year, six FBDOs involving groups of pilgrims, four among foreign tourists and two among Italians, were reported. Religious guesthouses were the setting of three FBDOs. The pathogens of FBDOs were mostly the same in the two periods: Salmonella, Staphylococcus aureus, Clostridium perfringens and Clostridium botulinum, as were the four most common food vehicles: sweets containing custard, fish, meat, and mushrooms. The pathogens of bacterial meningitis are mostly the same for the two periods: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, Streptococcus spp, Staphylococcus spp, Listeria monocitogens, Escherichia coli, and Acinetobacter spp.


Discussion
The number of cases and outbreaks of the targeted infectious diseases reported during the Millennium year among the residential population was slightly lower than the mean of the two previous years for meningitis and FBDOs, and slightly higher for Legionnaires' disease. The increasing trend in reported cases and outbreaks from 1995 to 1999 could be interpreted as an increase in surveillance sensitivity, which make us more confident in the validity of the figures for 2000 (Figure). Moreover, data from EDs are consistent with a good sensitivity of information gathered on health problems among foreign tourists. No atypical etiological agents in foodborne diseases or meningitis appeared. Similar results had been reported during the Olympic Games (2-4). Cases of legionnaires' disease reported by the international surveillance increased during the millennium year. We also found an increase of FBDOs involving foreign tourists. Thus, apart from the outbreaks and cases involving pilgrims or foreign tourists, the presence of 26 million visitors during the millennium year did not influence the epidemiology of these infectious diseases in the residential population of Lazio. The increase in cases among foreign tourists may not reflect an increase in incidence, but may instead be simply explained by the increase in the number of foreign visitors. The lack of data regarding the person-time spent by the visitors in the previous years makes it impossible to answer this question.
During the millennium year, the average size of the FBDOs was larger; this is attributable to a few large events. Religious guesthouses appeared prominently among communities involved in food borne outbreaks. They were used to house pilgrims, and their facilities had to prepare more food thus increasing the risk of FBDOs.
The incidence of bacterial meningitis, FBDOs, and legionnaires' disease, did not increase in January, April or August, the months with the largest gatherings. The anomalous summer peak of viral meningitis in August 2000 may be the consequence of one or more undetected clusters.

Some methodological problems should be highlighted. The data used for this study were limited only to two years: 1998 and 1999. This choice is due to the willing exclusion of 1997, the year the surveillance system was modified. Because of the brevity of the pilgrims' average stay in our region (2.5 days), the onset of symptoms tended to occur after their return to their countries of origin, especially in the case of viral meningitis, which has a long incubation period (10-15 days). This phenomenon is less relevant for FBDOs, because the incubation period is less than three days; while for legionnaires' disease, the international surveillance reports avoided losing cases diagnosed in other European countries.
Although this important event did not change the epidemiology of infectious diseases for residential population, an increased number of cases of legionnaires' disease and FBDOs among foreign tourists was reported with a high proportion of the FBDOs in religious guesthouses.


Acknowledgements

We would like to thank Dr Guido Bertolaso, Deputy Commissary of the 2000 Jubilee, and Dr Mario Rastrelli, Health Director for the Jubile 2000 for their support in the implementation of infectious disease control measures, the members of the Jubile Food Security Committee, Dr Paloa Aureli, the Istituto Superiore di Sanità (Italian Public Health National Institute), Dr Marco F.G. Jermini, the WHO European Centre for Health and Environment, Pr Adriano Mantovani, the WHO-FAO collaborating centre for vetenary public health and Pr Giovanni B. Quaglia, the national Italian institute for reaserch on foods and nutrition for their contributions in the courses for public health agents on the food security surveillance and the revision of HACCP on food production during the WYD.


References

1. Agenzia Romana per il Giubileo and Dipartimento del Turismo-Ministero dell'Industria. Giubileo del 2000: Sesto rapporto di previsione dei flussi di visitatori a Roma e provincia. Agenzia Romana per il Giubileo, Rome, 2000.
2. Jorm LR, Thackway SV, Churches TR, Hills MW. Watching the Games: public health surveillance for the Sydney 2000 Olympic Games. J Epidemiol Community Health, 2003; 57: 102-8.
3. Meehan P, Toomey KE, Drinnon J, Cunningham S, Anderson N, Baker E. Public health response for the 1996 Olympic Games. JAMA 1998; 279: 1469-73.
4. Pañella H, Plasència A, Sanz M, Caylà JA. An evaluation of the epidemiological surveillance system for infectious diseases in Barcelona Olympic Games of 1992. Gac Sanit 1995; 9: 84-90.
5. Hutchinson EJ, Joseph CA, Bartlett CLR on behalf of the European Working Group for Legionella Infections. EWGLI: a European Surveillance Scheme for Travel Associated Legionnaires' Disease. Euro Surveill 1996; 1: 37-9. (http://www.eurosurveillance.org/em/v01n05/0105-223.asp).
6. Giorgi Rossi P, Faustini A, Perucci CA, and the Regional Foodborne Disease Surveillance Group. Validation of guidelines for investigating foodborne disease outbreaks: the experience of the Lazio region, Italy. J Food Prot, 2003, in press.
7. CDC. Case definitions for infectious conditions under public health surveillance. MMWR Recomm Rep 1997; 46 (RR-10): 1-55. (http://www.cdc.gov/mmwr/PDF/rr/rr4610.pdf)

 



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