The purpose of this study was to examine the impact of influenza on hospitalization in the Netherlands. Two methods were applied to estimate this effect: (a) regression analysis and (b) comparison of hospitalization in epidemic years with non-epidemic years. Hospital discharge rates in 1984–93 have been considered. The study shows that, during the period studied, on average, almost 2700 people were hospitalized for influenza per annum, and that influenza was diagnosed as the main cause for hospitalization in only a fraction of these hospitalizations (326: 12%). From an economic perspective, these results imply that the cost-effectiveness of vaccination against influenza may be severely underestimated when looking only at changes achieved in the number of hospitalizations attributed to influenza.

Resident and transient Escherichia coli strains were identified in the rectal flora of 22 Pakistani infants followed from birth to 6 months of age. All strains were tested for O-antigen expression, adhesin specificity (P fimbriae, other mannose-resistant adhesins or type 1 fimbriae) and adherence to the colonic cell line HT-29. Resident strains displayed higher mannose- resistant adherence to HT-29 cells, and expressed P fimbriae (P=0·0036) as well as other mannose-resistant adhesins (P=0·012) more often than transient strains. In strains acquired during the first month of life, P fimbriae were 12 times more frequent in resident than in transient strains (P=0·0006). The O-antigen distribution did not differ between resident and transient strains, and none of the resident P-fimbriated strains belonged to previously recognized uropathogenic clones. The results suggest that adhesins mediating adherence to intestinal epithelial cells, especially P fimbriae, enhance the persistence of E. coli in the large intestine of infants.

The data of two cohort studies of HIV-infected individuals were used to examine whether the rate of CD4 decline is a determinant of HIV progression, independent of the most recent CD4 count. Time from seroconversion to clinical AIDS was the main outcome measure. Rates of CD4 decline were estimated using the ordinary least squares regression method. AIDS incidences were compared in individuals who had previously experienced either a steeper or a less steep rate of CD4 decline. Cox proportional hazards model including a time-dependent covariate for the rate of CD4 decline was performed. The rate of prior CD4 decline was significantly associated with the risk of developing AIDS independently from the most recent CD4 count, with a 2% increase in hazard of AIDS (P<·01) for a difference of 10 cells/mm3 in the estimated yearly drop in CD4 count. This finding gives scientific credit to the belief that individuals with a prior steeper CD4 decline consistently have a higher subsequent risk of developing AIDS than those with a less steep prior decline.

To determine the occupational significance of tick-borne zoonoses we sought serological evidence of Lyme borreliosis, human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE) in a representative sample of farmworkers. Although around 20% reported ticks on their domestic and companion animals, few (<2% per year) reported being bitten by ticks. Seroprevalence of Lyme borreliosis (0·2%), HME (0·2%) and HGE (1·5%) was low. Those seropositive for HGE were no more likely to report tick bites nor more likely to report ticks on their animals. This study provides evidence that farmworkers in England are exposed to tick-borne zoonoses but that they are uncommon. Since the severity of these diseases is linked to delays in diagnosis and treatment, clinicians should be aware of these diagnoses in patients from rural communities, with or without a self-reported history of tick bite.

Data from the national surveillance scheme for general outbreaks of intestinal disease, and the national laboratory reporting scheme were used to describe the epidemiology of small round structured virus (SRSV) infections in England and Wales. Between 1990 and 1995, there were 7492 laboratory reports of SRSV. Rates of reported illness were highest among infants, young children and the elderly. During 1992–5, some 707 SRSV outbreaks were reported. Outbreaks in hospital wards and residential facilities for the elderly accounted for 76% of the total, and annual numbers increased more than sixfold over the study period. There were wide regional variations in the numbers of SRSV outbreaks and laboratory reports. Both sporadic cases and outbreaks in the community are likely to be underestimated, but these passive surveillance systems provide an insight into the burden of SRSV infection among the institutionalized elderly.

Although food handlers are often implicated as the source of infection in outbreaks of food-borne viral gastroenteritis, little is known about the timing of infectivity in relation to illness. We investigated a gastroenteritis outbreak among employees of a manufacturing company and found an association (RR=14·1, 95% CI=2·0–97·3) between disease and eating sandwiches prepared by 6 food handlers, 1 of whom reported gastroenteritis which had subsided 4 days earlier. Norwalk-like viruses were detected by electron microscopy or reverse transcriptase-polymerase chain reaction (RT-PCR) in stool specimens from several company employees, the sick food handler whose specimen was obtained 10 days after resolution of illness, and an asymptomatic food handler. All RT-PCR product sequences were identical, suggesting a common source of infection. These data support observations from recent volunteer studies that current recommendations to exclude food handlers from work for 48–72 h after recovery from illness may not always prevent transmission of Norwalk-like viruses because virus can be shed up to 10 days after illness or while exhibiting no symptoms.

In 1993 an epidemic caused by dengue virus type 2 occurred in several North Queensland population centres. Charters Towers, estimated population 10000, had 155 officially notified cases. An analysis of symptoms was undertaken using a random sample of 1000 residents to determine specificity of symptoms, the subclinical infection rate, and to establish the true extent of the epidemic. Retrospective diagnoses of dengue fever were based on the presence of both serum dengue 2 neutralizing antibody and presence of symptoms. An estimated 20% of the population had dengue fever. The rate of subclinical infections in this epidemic was 14·6%. There were no symptoms that were specific for dengue fever. Bleeding occurred more frequently in people who recalled a previous dengue infection during a dengue 1 epidemic 12 years earlier (55·6% vs. 16·8%, P=0·003). Surveillance for future epidemics should be based on serological and virological confirmation of dengue virus infection amongst symptomatic patient.

An outbreak of hepatitis A started in late October 1996 in a nursery school in Tuscany, Italy. A programme of hepatitis A vaccination without the use of immunoglobulin started at the beginning of December 1996 and included 33 children, 21 household contacts and 6 adults working in the school. Overall, 11 cases occurred in children attending the school (attack rate 27%) and 10 among their household contacts (attack rate 9%). The latter also included parents, and, in two cases, grandmothers. The data indicate that susceptibility to HAV has increased over recent decades in central Italy. Past and recent experience shows that the usual duration of hepatitis A epidemics in the absence of immune prophylaxis is longer than that described here. The use of hepatitis A vaccine probably contributed to the early extinction of the outbreak, because no further cases were notified in the area after 7 February 1997.

Data on injecting anabolic steroid users, within the national Unlinked Anonymous HIV Prevalence Monitoring Survey of injecting drug users (IDUs) were analysed to determine their risk of acquiring blood borne viruses. One hundred and forty-nine participants who had injected anabolic steroids in the previous month were identified from 1991–6, contributing 1·4% of all participation episodes in the survey. Rates of needle and syringe sharing by steroid users were low. Three of the 149 (2·0%) had anti-HBc and none had anti-HIV in their salivary specimens. The prevalence of anti-HBc in steroid injectors was significantly lower than in heroin injectors, 275/1509 (18%) (P<0·001), or in amphetamine injectors, 28/239 (12%) (P<0·001). The risk of blood borne virus transmission amongst these steroid injectors is low, probably due to hygienic use of injecting equipment and low levels of sharing. It is important to distinguish steroid injectors from other IDUs because they are a distinct group in terms of lifestyle and injecting practice.

An age shift in rubella infection to young adults has occurred in Scotland since the introduction of a first dose measles, mumps and rubella (MMR) vaccination in 1988 and a second dose measles/rubella (MR) vaccination in 1994/95. The Health Board was alerted to an outbreak of rubella at Stirling University by the notification of 6 cases amongst male students aged 18–28 years with dates of onset between 3 March and 21 March 1996. In response, a MR vaccination campaign was conducted to enhance population immunity to rubella within the university population and to reduce the likelihood of further cases. A total of 1795 students, staff and visitors were vaccinated. Vaccine coverage of 46% was estimated to be sufficient to boost rubella immunity in full time male students in university accommodation to 88·7–91·0%, just above the upper critical level of herd immunity for rubella of 85–88%. Students in colleges and universities in the UK will remain at increased risk of outbreaks of rubella and measles until the cohort who have received a two dose schedule of MR form the bulk of the college population. It may be prudent for tertiary education colleges and other institutions in the UK with young adults living in shared residential accommodation to offer MR vaccination to new entrants, targeting those who have not previously received the vaccine, between now and the year 2000.

To assess the relative importance of ulcerative and non-ulcerative sexually transmitted disease in the transmission of HIV, a seroprevalence study was conducted on 2210 patients at the sexually transmitted diseases (STD) clinic of the S. Maria e S. Gallicano Hospital in Rome, between 1989 and 1994. Among male patients, by univariate analysis, strong predictors of HIV infection were homosexuality, sexual exposure to a HIV-positive partner, hepatitis B virus infection, and positive syphilis serology. An increased risk was estimated for patients with past genital herpes (odds ratio (OR) 3·86, 95% confidence intervals (CI) 0·40–18·2), and primary syphilis (OR 5·79, 95% CI 0·59–28·6). By multivariate analysis, a positive association was found with homosexuality (OR 6·9, 95% CI 2·9–16·5), and positive syphilis serology (OR 3·5, 95% CI 1·3–9·2). An adjusted OR of 2·41 was calculated for current and/or past genital herpes. These results, although not conclusive, suggest a role of ulcerative diseases as risk factors for prevalent HIV infection, and indicate that positive syphilis serology is an unbiased criterion for identifying individuals at increased risk of HIV infection.

Despite Department of Health recommendations, universal antenatal testing for hepatitis B virus (HBV) is not performed throughout Scotland. We describe the evaluation of an assay to document past or present infection with HBV, by identifying maternal antibody in routine Guthrie dried neonatal blood spot samples taken when infants are 7 days old. A modified haemagglutination assay to detect antibody to hepatitis B core antigen (CORECELL, Green Cross) was validated and found to be 79% sensitive (44/56) and 100% (105/105) specific when used with dried blood spot samples made from panels of serum of known reactivity. Ninety-three percent (13/14) of HBV carriers were CORECELL positive. Sixty-six (0·5%) of 14044 routine Guthrie samples taken from babies born in Scotland from June–August 1992 were CORECELL positive indicating past or present maternal infection with HBV. A cross-sectional survey would document the maternity hospitals where universal antenatal hepatitis B screening should be urgently established.

Surveillance of hepatitis A in residents of Eastern Sydney Health Area identified substantial epidemics in homosexual males in 1991–2 with a peak rate of 520 per 100000 recorded in males aged 25–29 years, and again in 1995–6, with a peak rate of 405 per 100000 per year in males aged 30–34 years. During 1994–5 an epidemic was detected among disadvantaged youth associated with injecting drug use; peak rates of 200 per 100000 per year were reported in males aged 25–29 years and of 64 per 100000 per year among females aged 20–24 years. The epidemiology of hepatitis A in these inner suburbs of Sydney is characterized by very few childhood cases and recurrent epidemics among homosexual men. Identified risk groups need to be targeted with appropriate messages regarding the importance of hygiene and vaccination in preventing hepatitis A. However, poor access to health services among disadvantaged youth and a constant influx of young homosexual males into these inner suburbs present major challenges to hepatitis A control.

Two indirect methods were used to estimate the point prevalence of HIV infection in England and Wales at the end of 1993 using data on diagnosed HIV infections, AIDS cases, HIV-related deaths and HIV testing behaviour from unlinked anonymous surveys. The methods estimated the proportion of all prevalent HIV infections that diagnosed infections represented. Most of those exposed to HIV infection through injecting drug use or sexual intercourse between men had had their infections diagnosed compared to less than half of those exposed through heterosexual intercourse. The total estimated number of prevalent infections was 22350 for the diagnosis interval method and 20540 for the test history method, and about 56–57% of these were in homo/bisexual men. These indirect methods are cheap and simple applications of surveillance data which provide estimates that compare favourably with those produced by more complex methods.

The present study examined the effect of hepatitis B virus (HBV) and alcohol intake, and the role of hepatitis delta virus (HDV) and hepatitis C virus (HCV) in the aetiology of chronic liver disease in Albania. A total of 106 cases of liver cirrhosis or chronic hepatitis were compared to 195 control patients without these or other liver diseases. Adjusted odds ratios were 52·7 (95% CI 22·7–122) for HBV surface antigen, 26·9 (95% CI 4·9–147) for anti-HCV, 26·2 (95% CI 3·1–221) for anti-HDV, 2.4 (95% CI 1·3–4·4) for lifetime alcohol intake and 2·3 (95% CI 1–5·5) for duration of alcohol intake. Although not significant, an interaction was suggested between HBsAg and anti-HCV and between HBsAg and alcohol intake. Our study underlines the role of hepatitis viruses in the development of chronic liver diseases. Additionally, it suggests that heavy alcohol intake may magnify the effect of HBV on these diseases. HBV vaccination and alcohol abstention appear to be important strategies to reduce the risk of liver cirrhosis and chronic hepatitis in Albania.

Mass vaccination can change the epidemiological dynamics of infectious diseases. It may result in a limited persistence of natural and vaccine-induced immunity and a higher mean age of infection, which may lead to a greater risk of complications. The epidemiological situation should be monitored and immunosurveillance based on the assessment of specific antibodies against vaccine-preventable diseases in human serum is one of the tools. In order to estimate the immunity of the Dutch population reliably, a large-scale, population-based, collection of serum samples was established (8359 sera in a nation-wide sampling and 1589 sera from municipalities with low vaccine coverage). In contrast to collecting residual sera from laboratories, this approach gains extensive information by means of a questionnaire regarding the determinants of the immune status and the risk factors for the transmission of infectious diseases in general. The population-based approach gives a better guarantee that the data are representative than collecting sera from laboratories does.

Risk factors for cervical infection with human papillomavirus (HPV) were assessed among 236 Italian women at risk for human immunodeficiency virus (HIV) infection (intravenous drug users (IVDU) or sexual partners of males at risk for HIV infection). All study participants underwent a structured interview, determination of HIV serostatus and detection of HPV cervical infection by means of polymerase chain reaction (PCR). Overall, the cervical presence of HPV DNA was ascertained in 86 of these 236 women (36·4%), while squamous intraepithelial lesions (SIL) were diagnosed in 57 (24·1%). HPV-infected and non-infected women did not differ in age, education and cigarette smoking. A statistically significant trend in the risk of HPV infection with increasing number of lifetime sexual partners was noted (P=0·01), but such trend was attenuated in multivariate analysis (multiple logistic regression (MLR) odds ratio (OR) for [ges ]20 partners vs 1=1·6, 95% confidence intervals (CI): 0·4–5·9). A nearly threefold higher risk of HPV cervical infection emerged among IVDU women (MLR–OR: 2·7, 95% CI: 1·4–5·0), and this difference was not influenced by HIV serostatus. The prevalence of HIV infection was higher among HPV-positive than HPV-negative women (62·8% and 54·0%, respectively) (MLR–OR=1·9, 95% CI: 0·9–3·8), and the proportion of women with less than 200 CD4+ cells/mm3 was slightly and not significantly higher among HPV-positive (47·1%) than negative women (37·2%).

Epidemiological research on respiratory syncytial virus (RSV) infections in children was carried out at the Virology Laboratory, University Teaching Hospital (UTH), in Lusaka, Zambia, from January–December 1996. Specimens including 736 nasal washings and 2424 throat swabs were collected from children with acute respiratory infections (ARI) and tested for RSV by enzyme immunoassay and by virus isolation. RSV was isolated in 62 (4·1%) of 1496 throat swabs collected from March to September and was detected in 99 (16·3%) of 609 nasal washings from March to November. The average RSV isolation rate was 2·6% and the average RSV detection rate was 13·5%. The highest RSV isolation (8·1%) and detection (30·5%) rates were in June 1996. RSV antibody in the 278 serum specimens collected from Zambian children, who were hospitalized in the paediatric ward, UTH, was detected using a standard neutralization test. The antibody positive rate was 60–80% in children >4 years. It is evident that RSV is one of the main causal agents of ARI in children in Zambia.

In 1989–91 anti-measles vaccination campaigns were conducted in several Italian regions to vaccinate all children aged between 13 months and 10–12 years without a history of measles or measles vaccination. This study was conducted to evaluate serological status after the mass vaccination campaigns. In 1994, capillary blood samples were collected from randomly selected children, aged 2–14 years, living in 13 local health units. Antibody titres were determined by ELISA. Blood spot samples were analysed for 4114 (75·6%) of 5440 selected children. Among the 835 that reported measles before 1990, 806 (96·5%) were immune and of the 2798 vaccinated, 2665 (95·2%) were immune. The Edmoston–Zagreb (E–Z) strain vaccine was associated with a lower level of immunity than the Schwarz (SW) strain. A history of measles identified almost all immune children. Vaccination with the SW strain conferred persistent immunity (at least 5 years) in 98% of vaccinees. The strategy was able to unite natural and induced immunity.

The status of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection among non-European Union (non-EU) immigrants in North-East Italy was evaluated. Among the 1683 individuals tested the prevalence of HBsAg was 8·9% (150 subjects) and of HBV antibodies (anti-HBc with/without anti-HBs) was 38·9% (654 subjects). The distribution of HBV serological markers showed significant differences according to region of origin; the highest prevalence of infection (76·9%) and carriage (16·1%) was found in immigrants from sub-Saharan Africa. Among the 933 individuals screened for HCV infection, prevalence of antibody was much lower (0·9%) than that observed in the Italian general population (3·2–12·6%). The large number of HBV carriers among immigrants could increase the number of new adult infections due to life-style habits or professional risks in the host population. In contrast, the risk of HCV spread from non-EU immigrants is very low.