The objective was to evaluate foodborne outbreaks of undetermined aetiology by comparing them to pathogen-specific epidemiologic profiles of laboratory-confirmed foodborne outbreaks. National foodborne outbreak data reported to CDC during 1982–9 were categorized by clinico-epidemiologic profiles based on incubation, duration, percent vomiting, fever and vomiting to fever ratio. From the pathogen-specific profiles, five syndromes were developed: a vomiting-toxin syndrome resembling Bacillus cereus and Staphylococcus aureus; a diarrhoea-toxin syndrome characteristic of Clostridium perfringens, a diarrhaeogenic Escherichia coli syndrome, a Norwalk-like virus syndrome, and a salmonella like syndrome. Of 712 outbreaks, 624 (87·6%) matched one of five syndromes; 340 (47·8%) matched the Norwalk-like syndrome and 83 (11·7%) matched the salmonella-like syndrome. After combining information on known pathogens and epidemiologic profiles, only 88 (12·4%) outbreaks remained unclassified. Norwalk-like virus outbreaks appear as common as salmonella-like outbreaks. We conclude that profiling can help classify outbreaks, guide investigations and direct laboratory testing to help detect new and emerging pathogens.

We compared gastroenteritis cases that consulted a general practitioner (GP) with those who did not in a community-based study and also with those in a GP-based study. We aimed to identify factors associated with consultation, and with inclusion of cases by GPs, and secondly to study the effects on the frequency of detection of pathogens. Furthermore, we estimated the under-ascertainment by GPs. Both studies were performed in The Netherlands in the same population in an overlapping time-period. Overall, 5% of community cases consulted a GP. Cases who consulted suffered from more severe episodes than non-consulting cases. Inclusion of cases by GPs, instead of a study team, caused a selection of more severe cases with more chronic symptoms. When extrapolating data from GP-based studies, it should be taken into account that, in general practice, gastroenteritis due to bacteria and Giardia lamblia is a relatively large proportion of that in the community and gastroenteritis due to Norwalk-like viruses is a relatively small proportion. The incidence of gastroenteritis in general practices was estimated between 14 and 35 per 1000 person years.

Campylobacter infection has one of the highest rates of all the notifiable diseases in Australia, with a peak in children aged 0–35 months. A matched case-control study was conducted to investigate risk factors for campylobacter infection for children in this age group. Eighty-one cases and 144 controls were enrolled in the study that was conducted between 24 January 1996 and 21 January 1997. The following risk factors were found to be independently associated with illness: ownership of pet puppies (adjusted odds ratio [OR] 16·58, 95% confidence interval [CI] 3·73–73·65) and pet chickens (OR 11·80, CI 1·37–101·75), and consumption of mayonnaise (OR 4·13, CI 1·61–10·59). We propose that children aged less than 3 years are at risk of campylobacter infection if residing in a household which has puppies or chickens as pets.

Typhoid fever is endemic in the South Pacific. We investigated an outbreak in Nauru. Through interviews and medical records, we identified 50 persons with onset between 1 October 1998 and 10 May 1999, of fever lasting [ges ]3 days and one other symptom. Salmonella Typhi was isolated from 19 (38%) cases. Thirty-two (64%) patients were school-aged children, and 17 (34%) were in four households. Case-control studies of (a) culture-confirmed cases and age- and neighbourhood-matched controls; and (b) household index cases and randomly selected age-matched controls implicated two restaurants: Restaurant M (matched OR [MOR] = 11, 95% confidence interval [CI] = 1·3–96) and Restaurant I (MOR = 5·8, 95% CI = 1·2–29). Food-handlers at both restaurants had elevated anti-Vi antibody titres indicative of carrier state. The annual incidence was 5·0/l000 persons. Outbreak-associated costs were $46000. Routine or emergency immunization campaigns targeting school-aged children may help prevent or control outbreaks of typhoid fever in endemic disease areas.

During outbreaks of Escherichia coli O157 a minority of patients with suspected infection develop haemolytic uraemic syndrome (HUS). The ability to identify this subgroup at an early stage is beneficial as mortality from HUS is high and may be influenced by intervention. During the 1996 Central Scotland E. coli O157 outbreak, of 886 patients from the community with suspected infection monitored at an outbreak clinic, nine developed HUS. We assessed factors associated with the development of HUS in this group. Children and the elderly were at increased risk of HUS. However, high white cell count was as least as good a predictor of HUS as age. High white cell counts predicted development of HUS with a sensitivity of 89%, specificity of 87%, positive predictive value of 7% and a negative predictive value of over 99%. We have used the results from this study along with other currently available evidence to propose a monitoring protocol for patients from the community with suspected E. coli O157 infection.

We describe six meningococcal disease outbreaks that occurred in Angola during the period 1994–2000. In total, 7140 cases were documented. The age groups most affected were 15–29 years and 5–14 years; there were no differences in incidence between the sexes. Circulation of both serogroup A and sporadic serogroup B strains was demonstrated. Mass vaccination campaigns with A+C meningococcal polysaccharide vaccine were implemented, except in Yambala province in 1999 where insecure conditions precluded this intervention.

Outbreaks of serogroup A meningococcal disease in Angola may indicate an extension of these epidemics outside the meningitis belt. Mass vaccination campaigns stopped the Angolan epidemics within weeks. Civil conflict and displaced persons living in crowded areas created serious difficulties for surveillance and impeded timely public health responses.

The aim of this study was to determine the prevalence of healthy Neisseria meningitidis pharyngeal carriers in a representative sample of the Catalonian school population, as well as its associated factors. The sample was divided into age groups: [les ]5, 6–7 and 13–14 years old. Parents were given a questionnaire to collect information on sociodemographic and epidemiological variables. Oropharyngeal swabs were collected with a cotton-tipped swab in an Amies transport medium and cultured on Thayer Martin plates at 35 °C in 5% CO2. The isolates were serogrouped and sero/subtyped. Of the 1406 children studied, 75 (5·34%) meningococcal carriers were detected: 63 B (4·5%), 9 non groupable (0·7%), 2 29E (0·1%) and 1X (0·07%). No serogroup C meningococci were found in this study, probably due to the high A+C vaccination coverage of up to 68·9% in children 6–7 years old. Bivariate analysis identified six statistically significant risk factors for meningococcal carriage: increasing age, recent upper respiratory tract infection, previous antibiotic treatment, number of students in the class, size of the classroom and social class. Multivariate analysis found that only age and previous antibiotic treatment remained statistically significant when the other factors were controlled.

The Republic of Ireland has the highest incidence of meningococcal disease in Europe with 40% of all cases occurring in children under the age of 5 years. Attending day-care increases the risk of certain infections, including Haemophilus influenzae type b (Hib) meningitis. The risk of meningococcal disease associated with day-care is not known. We conducted a case-control study among pre-school children with 130 laboratory-confirmed cases and 390 controls, matched on age, gender and place of residence, to determine if day-care attendance was a risk factor for meningococcal disease. Multivariate analysis showed that day-care attenders had a lower risk of disease than non-attenders (OR 0·3, 95% CI 0·1–0·7) whereas the number of adults in a household, and household crowding were independent risk factors for disease. Asymptomatic carriers of Neisseria meningitidis are the main source of transmission and these carriers are usually adults. Regular day-care attendance may reduce this risk by removing children from close and prolonged contact with adults.

We assessed the prevalence of carriage of methicillin-resistant Staphylococcus aureus (MRSA) in anterior nares and stools, and of third-generation cephalosporin resistant enterobacteriaceae and non-fermenting Gram-negative bacilli (RE/RNF) in stools of 748 hospitalized long-stay cirrhotic patients. We also evaluated the consequences of carriage on the epidemiology of hospital-acquired spontaneous bacterial peritonitis, bacteraemia and urinary tract infection (UTI) in these patients. The prevalence of carriage of MRSA and RE/RNF was 16·7% and 14·7% respectively. Whereas RE/RNF carriage did not lead to an increased risk of infection due to RE/RNF, the overall risk of infections caused by MRSA was more than tenfold higher in MRSA carriers. MRSA and RE/RNF carriers had received prior antibiotic therapy to a greater extent than non-carriers (P < 0·001) and MRSA carriers had received prior norfloxacin prophylaxis to a greater extent than the two other groups (P < 0·02). The mortality rate during hospital stay was higher in MRSA and RE/RNF carriers than in non-carriers (P < 0·001). Pugh score (P < 0·0001), age (P < 0·0001), MRSA carriage (P = 0·0018) and bacteraemia (P = 0·0017) were associated independently with mortality. MRSA carriage in hospitalized cirrhotic patients leads to the emergence of infections due to this strain, mainly SBP and bacteraemia. Prior antibiotic therapy and norfloxacin prophylaxis increase the risk of carriage of MRSA.

The immunogenicity and reactogenicity of the tetanus–diphtheria adult type vaccine was compared in two groups: group I (n = 201, 18–30 years old, presumably vaccinated with the DTP vaccine) and group II (n = 147, [ges ] 45 years old, without vaccination antecedents). Before vaccination, the seroprotection levels for tetanus were 90·5% (group I) and 30·6% (group II). These rose to 99·5% and 81·7%, respectively, after administration of one vaccine dose. For diphtheria, prevaccination seroprotection levels were 38·3% (group I) and 19·0% (group II). These rose to 85·8% and 65·7%, respectively, after vaccination. The logistic regression analysis showed an association between antibody titre and age. In group II, 3 doses of Td vaccine were needed to reach titres similar to those achieved in group I with a single dose. Stated reactogenicity was greater in: young subjects, women, those with higher titres of tetanus antibodies and those receiving other vaccines simultaneously. These results confirm the need for vaccination schedules adapted to the characteristics of each population age-group.

One fifth of 527 cases of hepatitis A occurred in self-identified injection drug users during a community-wide epidemic in Spokane County (Washington) in 1997–8. We hypothesized that an immunization campaign targeted at illicit drug users could control the epidemic. Starting in May 1998, hepatitis A vaccine was provided to individuals in jails and other sites frequented by illicit drug users. Volunteers at vaccination sites were surveyed about risk. Serial convenience samples of jail inmates who denied previous vaccination were anonymously tested for hepatitis A virus (HAV) immunoglobulin G (IgG). From May to December 1998, 2765 high-risk individuals were vaccinated against hepatitis A. The proportion of HAV IgG seropositive inmates increased from 30% to more than 50%. Our findings suggest that vaccination along with naturally occurring infection increased the rate of hepatitis A immunity among illicit drug users during the final months of the epidemic. This supports the hypothesis that targeted immunization of high risk groups may shorten the natural history of a community-wide epidemic.

This descriptive study investigated an outbreak of hepatitis A virus (HAV) infection among injecting drug users (IDUs) and their contacts. Twenty-seven cases of acute HAV infection were identified in a 5-month period. Connections with the local injecting drug using (IDU) population were established for 25 of the cases of whom 14 admitted to injecting drug use. HAV RNA genotyping revealed two HAV variants, closely related to variants found in Scandinavian IDUs and in South East Asia. The study demonstrates that once HAV enters the IDU population extensive outbreaks are possible. We recommend that all IDUs should be tested for HAV and hepatitis B virus (HBV) infections and offered combined hepatitis A and B vaccines if non-immune.

This study aimed to assess the seroprevalence and risk factors for hepatitis B virus (HBV), hepatitis C virus (HCV), and HIV-1 infections among injecting drug users (IDU) in New Mexico. Serological and behavioural surveys were conducted in conjunction with street-based outreach, education and HIV counselling and testing. High rates of antibody positivity for HCV (82·2%) and HBV (61·1%), and a low rate for HIV (0·5%) were found. In multivariate analyses, both HBV and HCV infection were positively associated with increasing age, increasing years of injection and heroin use. Receipt of a tattoo in prison/jail was associated with HBV (odds ratio = 2·3, 95% confidence interval 1·4, 3·8) and HCV (OR = 3·4, 95% CI = 1·6, 7·5) infections. Prevention of bloodborne pathogens among IDUs should focus on young users, early in their drug use experience. Studies examining the relationship between tattooing and HBV and HCV infection are needed as are efforts to promote sterile tattooing, in prisons and elsewhere.

The aim of the study was to elucidate the epidemiological features of Hepatitis C virus (HCV) infection among teenagers in an endemic area by conducting a mass screening study. We also investigated the clinical outcome of the anti-HCV-positive subjects by conducting subsequent short-term and long-term follow-up studies. All 2837 students of two junior middle schools in Tzukuan, aged 13–16 years, were invited to be screened for anti-HCV, HBsAg, AST and ALT in October 1995. A total of 2726 (96%) students responded. Anti-HCV, HCV RNA and aminotransferase levels were evaluated among anti-HCV-positive students 1 month and 30 months later, respectively. A total of 38 (1·4%; M/F = 22/16) participants were anti-HCV-positive. The anti-HCV-positive students had higher rates of exposures to transfusion, anti-HCV-positive families and surgery. The prevalence (2·8%) of the 7 maritime villages was markedly higher than that (0·7%) of the other 8 villages (P < 0·001). Subsequent follow-up studies demonstrated that there might be 5 cases of acute or recent HCV infection, and 6 cases who had recovered from chronic HCV infection.

In order to establish the differences in transmission pattern of varicella-zoster virus (VZV), a comparative seroepidemiological study was carried out in two different children samples. Children aged 1–11 years, were randomly selected from state schools of São Paulo city, Brazil. Individuals aged 1–15 years were sampled by cluster from Caieiras city. Children aged 3 years or under from Caieiras were not attending school, while those from São Paulo were attending all-day nurseries or kindergarten. The presence of antibodies to VZV was analysed by ELISA technique. The force of infection and contact rate were determined by mathematical techniques. The average age of first infection was 2·87±0·14 years and 4·07±0·47 years for São Paulo and Caieiras, respectively. The average force of infection estimated was 0·29 year−1 for São Paulo and was 0·26 year−1 for Caieiras. The proportion of seropositivity and the force of infection were higher in São Paulo school children up to 3 years of age compared with Caieiras children, where the social contact starts later. In conclusion, social changes affecting contact among children may influence varicella epidemiology.

Varicella is a disease caused by varicella-zoster virus. It is transmitted via the respiratory route, is highly communicable and mainly affects young children. An effective vaccine is now available, whose routine use is advised by health authorities in the USA and which can prevent severe disease, although breakthrough infections do occur. In deciding whether or not to include a vaccine in the routine vaccination schedule, knowledge of the morbidity of the disease in question is fundamental. Although reporting of varicella is compulsory in Catalonia, doctors only have to report the weekly number of cases diagnosed, and not their age distribution. Given that recent data on the prevalence of the infection in Catalonia according to age groups is available, it was considered that, using these data, an estimation of age-related incidence could be made.

The objective of the present study was to estimate the incidence of varicella in Catalonia on the basis of the available seroprevalence data. A curve was fitted to the observed prevalence and point prevalence estimates for all ages were obtained. The incidence was derived by smoothed prevalence for each of these age groups. Estimated variance of the estimated incidence was obtained by the delta method. Predicted prevalence in the 0–4 years age group was calculated by the smoothed prevalence.

The model that best fitted the sample prevalence was the exponential function. The estimated number of varicella cases in this study was 46419 (95% CI 40507–52270). As the population in Catalonia in 1996 was 6090040, the previous results give an incidence rate of 762·2 per 100000 persons/year with their 95% CI (666·1–858·3).

The method described may be applied to the study of incidence rates in relation to the prevalence of diseases if we accept that the infection produces permanent immunity; the risk of mortality is the same for infected and non-infected subjects and that the disease incidence and population remain constant in time.

A study investigating the causes of rash diseases using systematic laboratory testing was conducted in Niterói, Rio de Janeiro, between January 1994 to April 1998. Sera from 327 patients were tested for evidence of anti-rubella virus, measles virus, human parvovirus B19 and dengue fever virus specific immunoglobulin IgM and anti-human herpes virus type 6 (HHV-6) IgG antibodies. A laboratory confirmed diagnosis was achieved in 71·3% of the cases investigated: dengue fever (33·0%), rubella (20·2%), parvovirus B19 (9·2%), measles (6·7%) and HHV-6 (2·1%). No diagnosis was established for 94 cases (28·7%). An outbreak of measles was detected during 1997, with a peak in September and October. All of the diseases studied here presented with clinical features similar to measles and classical symptoms were found in all measles confirmed cases. The large overlap of combinations of signs and symptoms seen in this study highlights the difficulties of diagnosing a rash illness on clinical grounds alone.

To quantify the risk of human immunodeficiency virus (HIV) infection in children with tuberculosis (TB) a hospital-based, 1-year prospective, case-control study was performed in Addis Ababa, Ethiopia. Children with TB were compared to a control group of children admitted for elective surgery. The control group was also compared to a recent census of the background population. The crude odds ratio for HIV infection was 8·6 (95% CI 2·2–73). After adjustment for possible confounders in a multivariate regression model, the odds ratio for HIV infection in children with TB was found to be 12·7 (95% CI 2·9–55). Of several independent determinants of TB assessed in the study, this association was the strongest. Until HIV transmission has reached its peak, an increasing burden of dual infection among Ethiopian children is to be expected.

The epidemiological, clinical and therapeutic features of HIV disease diagnosed in 41 immigrants from outside of the European Union (EU), were compared with those of 123 Italian and EU patients, in a cross-sectional case-control study, with individuals matched according to age and gender. In total 4·15% of our patients came from outside of the EU (51·2% of them from subsaharan Africa), with a proportional predominance of females, and heterosexual and perinatal transmission of HIV disease (P < 0·0001 and P < 0·02, respectively). Compared with Italian and EU subjects, patients coming from abroad had a shorter duration of known HIV infection (P < 0·001), but only some subjects were aware of their HIV disease prior to immigration, or acquired HIV infection only after coming to Italy (14·6% and 12·2%, respectively). No cases of HIV-2 infection or co-infection were detected in either study group. Compared with controls, patients coming from outside of the EU had a comparable clinical and immunological status, and had similar antiretroviral therapy, which was administered earlier (P < 0·0001), and proved better tolerated (P < 0·04), than in Italian and EU subjects. The apparently more limited virological response (as expressed by a higher mean plasma viral load, and a lower rate of viral suppression at the last visit; P < 0·001 and P < 0·05, respectively), was probably a bias due to the shorter mean overall follow-up time (P < 0·0001), and the shorter mean duration of antiretroviral treatment (11·1±2·2 months of immigrants vs. 16·2±6·7 months of controls; P < 0·0001).

To study whether African-Americans are less likely than whites to present with cryptosporidiosis as an AIDS-defining condition (ADC), a case-control study was conducted using a large, population-based surveillance registry of AIDS patients in California. Data from January 1980 through June 1999 were analysed using risk factor stratification and multivariate logistic regression to evaluate confounding by other risk factors such as gender, injection drug use (IDU), CD4 counts, age and sexual orientation. Cases included 1373 subjects with cryptosporidiosis as an ADC and controls included 97419 subjects with other ADC. The results indicate a significantly lower risk for presentation with cryptosporidiosis as an ADC among African-Americans compared with whites (OR vs. whites = 0·5, 95% CI 0·4, 0·7). Additionally, there is evidence that heterosexuals are less likely than homosexual/bisexual males to present with cryptosporidiosis (OR = 0·5, 95% CI 0·4, 0·7). Our analyses also suggest a decreasing risk with increasing age. The possibility that there may be biologic factors or differential lifetime exposures that account for the difference between the racial/ethnic groups merits further investigation.