How immigration can change the prevalence of HBV infection in an urban area of Northern Italy

The introduction of HBV vaccination in Italy has led to a decline in new HBV infections. Increasing immigration over recent years suggests a change in short-term epidemiology of HBV. The aim of this study was to assess the prevalence of HBV infection in the general population living in the catchment area of Legnano Hospital (Northern Italy). In the period 2007-2008, 22,758 inpatients and outpatients were examined for Hepatitis B surface antigen (HBsAg), of whom 1,654 (7.3%) were of foreign origin. Of the 488 patients who were positive for HBsAg (2.1%), 381 (1.8%) were Italian and 107 (6.5%) were born in other countries. In terms of age, the prevalence of HBsAg was significantly higher among nonItalians in every age group (other than those aged >60 and <11 years), and in many of the selected subgroups: the inpatients of some departments (35.4% vs 17.2%), pregnant women (5.3% vs 0.3%), blood donors (4.7% vs 0.1%), and hospital staff (6.4% vs 1.3%). NonItalians were affected by 16.7% of acute infections and 24.3% of chronic infections; they also accounted for 42.6% of subjects with carrier state, 16.0% of patients with chronic hepatitis, and 12.2% of patients with cirrhosis. In our area, the overall prevalence of HBsAg among Italians is less than 2% (as expected following the introduction of HBV vaccination), but it is significantly higher among patients from areas highly endemic for HBV infection who represent a new reservoir for HBV infection. Introduction HBV is ubiquitous, but the prevalence of infection is diferent from region to region. There are countries in which the endemic seroprevalence of HBsAg (Hepatitis B Surface Antigen) is 8% or more (Africa and parts of Asia), countries with an intermediate seroprevalence of 2-7% (the Mediterranean basin, the Middle East and some Eastern European countries), and countries with a low seroprevalence of less than 2% (Western Europe, and North and South America except for some Brazilian and Peruvian regions).1 In the 1970s and 1980s, Italy was a country with intermediate endemic seroprevalence (about 3.5% of the population was HBsAg positive), with considerable geographical variation between the north and south.2 Over the last 30-40 years, the epidemiology of HBV in Italy has changed greatly for a number of reasons: improved socioeconomic conditions, better hygiene standards and educational campaigns against HIV. In 1983, selective vaccination for people at risk and in 1991, compulsory vaccination for all children aged 12 years and infants within the first year of life started.3,4 As a result of all these factors, the incidence of acute hepatitis and the prevalence of HBsAg carriers have both greatly decreased. The incidence of acute hepatitis B fell from 10.4 cases per 100,000 inhabitants in 19875 to 1.3 in 2005.6 The decline occurred in all age groups but was particularly evident in subjects aged 15-24 and 0-14 years. At general population level, the decline in the prevalence of HBsAg has been widely documented:7-12 for example, among pregnant women, the prevalence of HBsAg decreased from 2.4% in the 1980s to less than 1% in the year 2000.2,13,14 In general, Italy is now considered as being at low endemic as the prevalence of HBsAg carriers is estimated to be <2%,15 and most of them are aged over 40 years, probably due to a cohort effect as most of the infections were acquired in the past.2 Increased immigration in recent years has led to the arrival in Italy of a growing number of patients from countries that are highly endemic for HBV: it has been estimated that there are about 3.8 million immigrants in Italy, about 6% of the population.16 Consequently, the prevalence of HBV might be rapidly changing: 14% of the cases of acute hepatitis in 2004-2005 affected patients from Eastern Europe, Asia or Africa.6 The aim of this study was to evaluate the epidemiology of HBV in the population (of Italian and foreign origin) belonging to the catchment area of Legnano Hospital in 2007-2008. Materials and Methods The hospital is located in an urban area of Northern Italy near Milan, and its catchment area has a population of approximately 250,000 inhabitants. It includes both general and specialised medical and surgical departments, and has points for collecting blood samples from outpatients referred to us by their general pratictioners (GPs) for laboratory tests. Between January 1st, 2007 and December 31st, 2008, 22,758 subjects underwent a HBsAg test (Hepanostika HBsAg Ultra and Hepanostika HBsAg Ultra Confirmatory, BioMérieux, Boxtel, The Netherlands), 11,007 males (48.4%) and 11,751 females (51.6%) with a mean age of 48 years (range 0-104): 5530 (24.3%) samples came from inpatients (1267 [5.6%] admitted to the Infectious Diseases, Internal Medicine and Gastroenterology departments, 225 [1.0%] admitted to the Nephrology Unit, and 4038 [17.7%] admitted to other general or specialist medical or surgical departments); 8611 samples (37.8%) came from outpatients referred by their GPs for clinical checks (5719: 25.1%) or HBsAg screening in pregnancy (2892: 12.7%); 441 samples (1.9%) were received from the Occupational Medicine Unit supervising hospital staff; and 8176 (35.9%) came from the Blood Transfusion Centre for pre-transfusion screening (6814: 29.9%) or to check the suitability of candidates for donation (1362: 6.0%). A total of 1654 samples (7.3%) came from as many people of nonItalian origin (born abroad and of non-Italian nationality). In case of the HBsAg-positive subjects, clinical and laboratory files were retrospectively searched for personal and clinical data regardMicrobiology Research 2011; volume 2:e21 Correspondence: Massimo De Paschale, Microbiology Unit, Hospital of Legnano, via Papa Giovanni Paolo II, 20025 Legnano (Milan), Italy Tel: +39.0331.449319 Fax: +39.0331.449578. E-mail: massimo.depaschale@ao-legnano.it


Introduction
HBV is ubiquitous, but the prevalence of infection is diferent from region to region.There are countries in which the endemic seroprevalence of HBsAg (Hepatitis B Surface Antigen) is 8% or more (Africa and parts of Asia), countries with an intermediate seroprevalence of 2-7% (the Mediterranean basin, the Middle East and some Eastern European countries), and countries with a low seroprevalence of less than 2% (Western Europe, and North and South America except for some Brazilian and Peruvian regions). 1n the 1970s and 1980s, Italy was a country with intermediate endemic seroprevalence (about 3.5% of the population was HBsAg positive), with considerable geographical variation between the north and south. 2 Over the last 30-40 years, the epidemiology of HBV in Italy has changed greatly for a number of reasons: improved socioeconomic conditions, better hygiene standards and educational campaigns against HIV.In 1983, selective vaccination for people at risk and in 1991, compulsory vaccination for all children aged 12 years and infants within the first year of life started. 3,4As a result of all these factors, the incidence of acute hepatitis and the prevalence of HBsAg carriers have both greatly decreased.The incidence of acute hepatitis B fell from 10.4 cases per 100,000 inhabitants in 1987 5 to 1.3 in 2005. 6The decline occurred in all age groups but was particularly evident in subjects aged 15-24 and 0-14 years.At general population level, the decline in the prevalence of HBsAg has been widely documented: [7][8][9][10][11][12] for example, among pregnant women, the prevalence of HBsAg decreased from 2.4% in the 1980s to less than 1% in the year 2000. 2,13,14In general, Italy is now considered as being at low endemic as the prevalence of HBsAg carriers is estimated to be <2%, 15 and most of them are aged over 40 years, probably due to a cohort effect as most of the infections were acquired in the past. 2 Increased immigration in recent years has led to the arrival in Italy of a growing number of patients from countries that are highly endemic for HBV: it has been estimated that there are about 3.8 million immigrants in Italy, about 6% of the population. 16Consequently, the prevalence of HBV might be rapidly changing: 14% of the cases of acute hepatitis in 2004-2005 affected patients from Eastern Europe, Asia or Africa. 6The aim of this study was to evaluate the epidemiology of HBV in the population (of Italian and foreign origin) belonging to the catchment area of Legnano Hospital in 2007-2008.

Materials and Methods
The hospital is located in an urban area of Northern Italy near Milan, and its catchment area has a population of approximately 250,000 inhabitants.It includes both general and specialised medical and surgical departments, and has points for collecting blood samples from outpatients referred to us by their general pratictioners (GPs) for laboratory tests.Between January 1st, 2007 and December 31st, 2008, 22,758 subjects underwent a HBsAg test (Hepanostika HBsAg Ultra and Hepanostika HBsAg Ultra Confirmatory, BioMérieux, Boxtel, The Netherlands), 11,007 males (48.4%) and 11,751 females (51.6%) with a mean age of 48 years (range 0-104): 5530 (24.3%) samples came from inpatients (1267 [5.6%] admitted to the Infectious Diseases, Internal Medicine and Gastroenterology departments, 225 [1.0%] admitted to the Nephrology Unit, and 4038 [17.7%] admitted to other general or specialist medical or surgical departments); 8611 samples (37.8%) came from outpatients referred by their GPs for clinical checks (5719: 25.1%) or HBsAg screening in pregnancy (2892: 12.7%); 441 samples (1.9%) were received from the Occupational Medicine Unit supervising hospital staff; and 8176 (35.9%) came from the Blood Transfusion Centre for pre-transfusion screening (6814: 29.9%) or to check the suitability of candidates for donation (1362: 6.0%).A total of 1654 samples (7.3%) came from as many people of non-Italian origin (born abroad and of non-Italian nationality).
In case of the HBsAg-positive subjects, clinical and laboratory files were retrospectively searched for personal and clinical data regard-

N o n -c o m m e r c i a l u s e o n l y
ing the type of infection (chronic or acute), whenever possible, they were divided into incident cases (patients diagnosed as having chronic hepatitis for the first time during the study) and prevalent cases (patients diagnosed as having chronic hepatitis before the study period).The clinical diagnoses were based on liver biopsy data when a biopsy was performed.In the absence of a liver biopsy, chronic hepatitis was diagnosed on the basis of the presence of fluctuating or persistently high aminotransferase levels for more than six months, and high HBV-DNA levels (>2000 IU/mL) in the absence of clinical, biochemical and ultrasound markers of cirrhosis; cirrhosis was diagnosed on the basis of clinical, biochemical and ultrasound signs; 17 and hepatocellular carcinoma (HCC) was diagnosed on the basis of alpha 1-fetoprotein values of >400 ng/mL confirmed by at least one imaging technique demonstrating a typical vascular pattern. 18The patients were included in the group of subjects with carrier state if they were HBeAg-negative/anti-HBe-positive, had persistently normal transaminases, and HBV DNA levels of <2000 IU/mL. 19he data were statistically analysed using the c 2 test and Fisher's exact test.

Results
A total of 488 subjects (2.1%) were positive for HBsAg, of whom 107 (21.9%) were of non-Italian origin.The analysis of 384 medical records documented acute infection in 18 cases (4.7%) and chronic infection in 366 (95.3%); three of the acute infections (16.7%) and 89 of the chronic infections (24.3%) involved non-Italians.
The 316 investigated patients with chronic infection included 141 (44.6%) who were asymptomatic (carrier state), 119 (37.7%) with chronic hepatitis, 49 (15.5%) with cirrhosis, and seven (2.2%) with HCC.The proportions of non-Italians were 42.6% of the subjects with carrier state, 16.0% of the patients with chronic hepatitis, 12.2% of those with cirrhosis, and 0% of those with HCC: globally, 14.3% of the symptomatic forms were found in non-Italian patients.
Table 2 shows the prevalence of HBsAg stratified by the geographical origin of the subjects.The difference from its prevalence among Italians was statistically significant for all of the subjects except those coming from Western Europe/North America and Latin America.Table 3 shows the prevalence data stratified by age and Table 4 shows the prevalence data stratified by hospital department of origin.The overall prevalence among the blood donors was 0.1% (9/8,176).In particular, among the 6814 regular donors, only one was positive (seroconversion) (0.01%, 95% CI: 0.00-0.03); the remaining eight (0.6%, 95% CI: 0.19-1.01)were all among the 1362 candidates for donation.

Discussion
The use of anti-HBV vaccination in Italy (together with improved socioeconomic and hygienic conditions) has led to a reduction in the prevalence of Italian HBsAg carriers to fewer than 2%. 20On the other hand, the recent increase in immigration has led to a growing number of residents coming from countries that are highly endemic for HBV.The 2.1% prevalence of HBsAg-positive subjects found in our study is slightly higher than expected (our    area is now at intermediate endemic seroprevalence), but one-fifth of this is due to people of foreign origin, among whom the overall prevalence of HBsAg is significantly higher than that of patients of Italian origin.Prevalence rates vary greatly among people coming from different countries.

Article
Nevertheless, our calculated rates may be underestimated because it is known that a number of immigrants refuse contact with public health services for fear of expulsion or because they have specific cultural, religious or psychological attitudes towards medical practices. 21he fact that about half of our incident cases involved non-Italians (who accounted for only 16.9% of the prevalent cases) is in line with the rapid increase in non-Italian (and HBsAgpositive) residents in our area.However, the prevalence among Italians should be sufficiently indicative of the population in our area, albeit with some limitations (very small number in the <11 years).In terms of age, the higher prevalence of HBV infection among non-Italians held true for all age groups between 11 and 60 years.There were no cases among the subjects aged >60 years, which reflects the fact that the average age of the immigrant population is less than that of the Italian population and so there are very few non-Italians in this age group: only 2% as against 22.4% of the Italians.Unlike that among non-Italians, the prevalence among Italians increases with age and is more than 2% only in subjects aged >50 years.This is due to the vaccination campaign which has especially protected younger subjects.
The overall prevalence is the sum of various components and includes different groups with different prevalence rates.Prevalence among the subjects admitted to our Infectious Diseases, Gastroenterology and Internal Medicine departments was of course higher because they are reference centres for the diagnosis and treatment of liver diseases: nearly one-fifth of the patients were HBsAg positive and the prevalence among non-Italians was twice that among Italians.The patients from the other departments reflect the general population of patients hospitalised because of diseases other than liver diseases, but there was no difference in prevalence between Italians and non-Italians, probably because of the lack of homogeneity in terms of the presence of non-Italians: for example, they accounted for only 2.7% of the samples coming from Nephrology Unit.
The outpatients included individuals of all ages who for various reasons were referred to us by their GPs for a check-up or baseline screening, such as pregnant women who represent a healthy female population of childbearing age.The prevalence of 0.3% among Italian women was lower than that in the group of non-Italian women (5.3%) and underlines the importance of antenatal screening in this group.Foreign women are less adherent to screening than Italian women because of cultural differences and language problems 14 and efforts should be made to increase compliance. 22he 1.3% prevalence among the Italian hospital staff may be overestimated because hospital personnel are serologically monitored every three years and in the event of an accident involving a biological risk, and is required for all new entrants.The finding is therefore more a reflection of the general situation than the situation among hospital staff in particular.Our hospital has about 2200 employees, and only 441 were examined in the study period.Once again, the higher prevalence among non-Italians has to be taken into account because the recent increase in immigration has naturally led to an increase in the number of non-Italian healthcare workers.
Regular blood donors represent a highly selected population of subjects characterised by the known absence of HBsAg and other markers of active HBV infection over time.In our study the prevalence of HBsAg-positive donors was 0.1% (it was 1.68% in the Northern Italy in the 1980s 23 ), but there was only one case of infection (revealed by serum conversion) among regular donors: the other eight cases involved candidates for donation.In this group, the lower overall prevalence of 0.6% was due to the number of young (76.3% under the age of 40 years) and vaccinated subjects (43.0%) (data not shown).Once again, the difference between Italians and non-Italians was statistically significant, but the number of non-Italian blood donors is still very low.Blood donation in Italy is not paid and therefore does not attract people seeking a means of increasing their income as in some other countries, but requires a certain level of cultural and economic integration.
In conclusion, the overall prevalence of HBsAg among Italians in our area is less than 2%, as was expected following the introduction of vaccination, whereas the prevalence among subjects coming from areas that highly endemic for HBV is more than three times higher.These people therefore represent a reservoir for new HBV infection.They also account for one-seventh of all subjects with symptomatic liver disease.They are therefore also important in terms of health costs, which can only increase given the growing rate of immigration to Italy.All of this represents a challenge that needs to be faced if it is wanted to eradicate or otherwise control HBV infection.