Salmonella constitutes a genus of zoonotic bacteria of worldwide economic and health importance. The current view of salmonella taxonomy assigns the members of this genus to two species: S. enterica and S. bongori. S. enterica itself is divided into six subspecies, enterica, salamae, arizonae, diarizonae, indica, and houtenae, also known as subspecies I, II, IIIa, IIIb, IV, and VI, respectively [1]. Members of Salmonella enterica subspecies enterica are mainly associated with warm-blooded vertebrates and are usually transmitted by ingestion of food or water contaminated by infected faeces. The pathogenicity of most of the distinct serotypes remains undefined, and even within the most common serotypes, many questions remain to be answered regarding the interactions between the organism and the infected host.

Salmonellosis manifests itself in three major forms: enteritis, septicaemia, and abortion, each of which may be present singly or in combination, depending on both the serotype and the host involved. Although currently over 2300 serovars of Salmonella are recognized, only about 50 serotypes are isolated in any significant numbers as human or animal pathogens [2, 3] and they all belong to subspecies enterica. Of these, most cause acute gastroenteritis characterized by a short incubation period and a severe systemic disease in man or animals, characterized by septicaemia, fever and/or abortion, and such serotypes are often associated with one or few host species [4–6].

It is the intention of this review to present a summary of current knowledge of these host-adapted serotypes of S. enterica. The taxonomic relationships between the serotypes will be discussed together with a comparison of the pathology and pathogenesis of the disease that they cause in their natural host(s). Since much of our knowledge on salmonellosis is based on the results of work on Typhimurium, this serotype will often be used as the baseline in discussion. It is hoped that an appreciation of the differences that exist in the way these serotypes interact with the host will lead to a greater understanding of the complex host–parasite relationship that characterizes salmonella infections.

The number of human visitors to Antarctica is increasing rapidly, and with it a risk of introducing infectious organisms to native animals. To study the occurrence of salmonella serotypes in sub-Antarctic wildlife, faecal samples were collected from gentoo penguins, macaroni penguins, gray-headed albatrosses, black-browed albatrosses and Antarctic fur seals on Bird Island in the South Georgian archipelago during the austral summer of 1996 and 1998. In 1996, S. havana, S. typhimurium and S. enteritidis were isolated from 7% of gentoo penguins and 4% of fur seals. In 1998, however, 22% of fur seals were found to be infected with S. havana, S. enteritidis and S. newport. All isolates, except one, showed identical pulsed-field gel electrophoresis-patterns within each serotype, irrespective of sampling year and animal reservoir. No significant antibiotic resistance was found. The very low heterogeneity in the salmonella isolates found could either indicate a high genetic adaptation of the bacteria to the environment or a recent introduction of salmonella into the area.

A Mix-ELISA using lipopolysaccharide antigens from Salmonella enterica serotype Enteritidis and Typhimurium was evaluated using samples collected over time in the Danish salmonella surveillance programme for poultry. Serological samples (n = 42813) taken from broiler-breeder flocks after a year of bacteriological monitoring with negative results were used for calculating the flock and individual test specificities, which were 0·997 and 0·999, respectively. Layer flocks from the table egg sector were used for calculation of positive predictive values. In the survey, flocks were examined for salmonella by Mix-ELISA and by faecal culture, and in case of a positive result in either of these a repeated, serological testing was performed, and 60 animals were organ-cultured. If one of these samplings was positive, the flock was declared salmonella infected. In a period of 3 months, 35 flocks were found to be positive in the routine samples. Of these, 32 were serologically positive, 2 both serologically and faecally positive and 1 flock only faecally positive. For flocks serologically positive in the surveillance programme, a positive-predictive value of 0·62 for organ culture positivity was found, and while considering serological follow-up samples, the value was 0·95.

A case-control study was conducted in western Sweden (Älvsborg County). The aim of the study was to identify any special food items or behaviours associated with an increased risk of contracting campylobacter infection. A total of 101 cases and 198 controls were matched for age, sex and district of residence. The following risk factors or risk behaviours were associated with campylobacter infection: drinking unpasteurized milk (OR 3·56, 95% CI 1·46–8·94), eating chicken (OR 2·29, 95% CI 1·29–4·23), or eating pork with bones (chops OR 2·02, 95% CI 1·17–3·64; loin of pork OR 1·83, 95% CI 1·07–3·12), barbecuing (OR 1·98, 95% CI 1·10–4·34), and living or working on a farm (farm OR 3·06, 95% CI 1·58–6·62, hen/chicken-breeder OR 3·32, 95% CI 1·56–6·78), daily contact with chickens or hens (OR 11·83, 95% CI 3·41–62·03).

In the UK the increasing use of pre-admission parenteral antibiotic therapy in meningococcal disease has lessened the value of routine cultures as a tool to confirm diagnosis, and laboratory confirmation of invasive meningococcal infection is achieved increasingly by non-culture, nucleic acid amplification methods. The purpose of this study was to evaluate a DNA extraction and meningococcal-specific DNA amplification methodology for detection of meningococci from oropharyngeal swabs.

One hundred and six swabs from suspected or confirmed cases of meningococcal disease, and 94 swabs from contacts of meningococcal disease cases were examined. Of laboratory-confirmed cases, 38/65 (58·5%) yielded a positive oropharyngeal swab PCR result and 5/24 (20·8%) swabs from suspected but laboratory-unconfirmed cases were PCR positive. No significant differences in PCR positivity rates were found between the types of swab transport systems utilized, but transport time to the testing laboratory was found to affect PCR positivity (P < 0·05).

Application of meningococcus-specific PCR to oropharyngeal swabs, in addition to routine culture of swabs, can provide valuable epidemiological information as well as case confirmation for contact management. PCR amplification of meningococcal PCR from oropharyngeal swabs will also increase the ascertainment in swabbing surveys carried out as part of meningococcal disease outbreak investigation and management.

A new variant within the electrophoretic type (ET)-37 complex of Neisseria meningitidis, ET-15, first detected in Canada in 1986, has been associated with severe clinical infections and high mortality rates in several European countries, Israel and Australia. To ascertain the genetic and epidemiological relationships of ET-15 strains from different geographical areas, 72 ET-15 isolates from 10 countries were compared to 13 isolates representing other clones of the ET-37 complex. The 85 strains were analysed by pulsed-field gel electrophoresis (PFGE) using 2 restriction endonucleases and Southern hybridization with 10 genetic markers. Four ET-15 strains and 4 other strains of the ET-37 complex were further examined using an additional restriction enzyme and a total of 18 genetic markers. PFGE fingerprints of the ET-15 strains were closely related. Strains within each country were even more closely related, suggesting single introductions of the clone. Physical mapping of genes in ET-15 and other strains of the ET-37 complex demonstrated that large genetic rearrangements of the genome have occurred in association with the appearance of the ET-15 variant.

Twenty-six isolates of the newly designated M90 serotype group A Streptococcus (GAS) from a large food-borne outbreak of pharyngitis in Greece and six M90 sporadic isolates from UK, were typed by pulsed-field gel electrophoresis (PFGE). Twenty-four outbreak isolates were identical and two closely related. The Greek isolates were possibly related with one UK isolate, while other sporadic isolates exhibited distinct PFGE profiles from the former isolates.

Listeria monocytogenes was isolated from critical control points in a Danish turkey processing plant, from turkey products and from cases of human listeriosis. During processing in the plant the prevalence of L. monocytogenes ranged from 25·9 to 41·4%. Cleaning and disinfection decreased the prevalence to 6·4%. Isolates of L. monocytogenes were characterized by pulsed-field gel electrophoresis (PFGE) using restriction endonuclease ApaI. Identical DNA types were obtained from turkey products and the processing line even after cleaning and disinfection. Two identical DNA types were demonstrated among isolates from turkey products and human cases of listeriosis. The prevalence of L. monocytogenes in turkey products ranged from 7·3 to 17·4% for ready-to-eat products and raw products, respectively. Since none of the 27 flocks examined before slaughter sampled positive for L. monocytogenes and the prevalence increased during processing, the potential risk from turkey meat was apparently due to factory hygiene rather than intrinsic contamination of the turkeys.

Brucellosis is known to occur in Yemen but its epidemiology has not been extensively studied. The present investigation examined risk factors for human brucellosis in Yemen using a hospital-based case-control study. A total of 235 consecutive patients with brucellosis attending the Central Health Laboratory in Sana’a, Yemen, were matched in respect of age, sex, and place of residence, rural or urban, with 234 controls selected from individuals attending the Central Health Laboratory for unrelated health problems. Clinical information on patients and controls was supplemented with occupational and socio-economic data obtained by interview of cases and controls using a standard questionnaire.

After controlling for confounding factors significant risk factors for infection related to occupation as a farmer (OR 2·5 (95% CI 1·4–4·5, P < 0·0001)), shepherd (OR 7·8 (95% CI 1·0–61, P 0·05)) or microbiologist (OR 24·5 (95% CI 2·9–204, P 0·003)); and drinking fresh milk (OR 2·0 (95% CI 1·3–4·3, P 0·001)) and laban (OR 22·7 (95% CI 1·7–4·2 P < 0·0001)). Taking other milk products and offal were not risk factors. Socio-economic and educational factors were also independent risk factors. Occupational, food and socio-economic risk factors significantly confounded one another.

Yemen shares some but not all of the risk factors of neighbouring countries. The interrelation between the various factors is complex and studying any one in isolation may give a false impression of its public health significance. Control through education of the population to minimize exposure to, and contact with, animals and their milk and milk products and to boil milk before drinking it or using it to make buttermilk, would be difficult as these would represent such fundamental changes to established patterns of behaviour of this society. Ideally there would be a campaign to control the infection by animal vaccination but the costs and logistic difficulty would be great. Presently there is a clear need for doctors in Yemen to be made aware of the frequency of this infection, the means available for clinical and laboratory diagnosis and effective treatment, while strategies to control the disease in Yemen are formulated and field tested.

The Department of Veterans Affairs operates a large, centrally administered health care system consisting of 173 hospitals and 4 free standing outpatient clinics nationwide with approximately 945115 hospital discharges, 24·2 million outpatient visits, and 2·86 million persons served annually over the time frame of the review. The purpose of the study was to define whether such a system could effect timely change in the incidence of tuberculosis (TB) using centralized programme planning and flexible field implementation. A retrospective review of the number of newly diagnosed cases of active TB treated at veterans health care facilities between 1 October 1990 and 30 September 1997 was determined by using a standardized annual case census.

Intervention included implementation of the most current guidelines for the prevention of transmission of TB in the community and hospital setting, including administrative and engineering controls and a change in personal protective equipment. Centrally directed programme guidance, education, and funding were provided for field use in health care facilities of widely varying size and complexity.

The numbers of total reported cases of TB decreased significantly (P < 0·001) throughout the veterans health care system (nationally and regionally), with the case rate decreasing at a rate significantly greater than that seen in the USA as a whole (P < 0·0001). TB associated with multi-drug resistance (isoniazid and rifampin) and HIV coinfection also significantly decreased over the study period. Therefore, a large, centrally administered health care system can effectively combat a re-emerging infectious disease and may also demonstrate a successful outcome greater than seen in other, perhaps less organized health care settings.

An outbreak of gastro-enteritis occurred in La Neuveville, township with 3358 inhabitants. A retrospective cohort study of 1915 participants showed that 1607 (84%) had been ill. Campylobacter jejuni was isolated from 28 patient faecal samples, Shigella sonnei from 21 patients and small round structured viruses (SRSV) from 6 patients. More than one pathogen was identified in eight persons. The epidemic curve was characteristic of a point-source outbreak. The risk for illness was significantly higher among persons who had drank unboiled drinking water than among those who had not (1290 [80·3%] of 1607 vs. 86 [27·9%] of 308; RR = 2·87; 95% CI 2·40–3·45). Risk increased significantly with the quantity of water consumed (P < 0·00 × 10−6). An SRSV isolate from water and one human faeces had an identical DNA sequence. The outbreak was due to a pump failure producing a spill of sewage into the groundwater. We conclude that transmission was waterborne and that measures including early warning, basic hygiene and sanitation improvements controlled this epidemic.

Data relating to 3313 adenovirus isolates from patients in Greater Manchester, UK between 1982 and 1996 were analysed using χ2 tests and 95% confidence intervals. Of the 3098 isolates that were typed, 18·6% were serotype 2, 14·9% serotype 3, 12·1% serotype 1 and 10·9% serotype 41. There was evidence of a seasonal occurrence of serotype 7 (March–August), serotype 2 (January–April), serotype 4 (June–August) and subgenus F (September–November). Children less than 5 years old were the most common group of patients with adenovirus infection (61·3%) compared to 24·2% for adults and only 5·6% for school children (5–15 years). Gastric symptoms were the most common amongst infants (47·6%) followed by respiratory (27·5%) and general symptoms (12·9%). In adults, the overwhelming clinical condition was conjunctivitis (88·9%). Despite the traditional association with adenoviruses, remarkably few cases of pharyngoconjunctival fever were recorded (1·7%).

Most of the countries in western Europe have now implemented mass infant rubella immunization programmes, instead of or in addition to selective vaccination in order to achieve the elimination of congenital rubella syndrome.

The European countries Denmark, England and Wales, Finland, France, Germany, Italy and the Netherlands undertook large, national serological surveys collecting several thousand serum specimens during 1994–8. Antibodies against rubella virus were detected by a variety of enzyme immuno-assays. Comparability of the assay results was achieved by a standardized methodology. The age- and sex-stratified serological results were related to the schedules, coverage of rubella vaccination and the incidence in these countries.

The results show widely differing levels of immunity to rubella both in the general population and in the specific age groups of males and females. A low rate (< 5%) of susceptibles in childhood and adolescents of both sexes was obtained only in Finland and the Netherlands.

Countries such as Italy with only moderate coverage for the infant immunization programme currently have both high susceptibility levels in the general population and in the at-risk population. The likelihood is of continued epidemics of rubella with cases of congenital rubella syndrome. The continued implementation of selective vaccination will help to offset the impact of this ongoing transmission and to protect women on reaching childbearing age.

A review of the epidemiology of clinical rubella in the Perm region of the Russian Federation from 1979–97 showed that the incidence was about 220 cases per 100000 population. Congenital rubella syndrome (CRS) accounted for 15% of birth defects and for about 3·5 cases of CRS per 1000 live births per year. Surveys of the seroepidemiology of rubella infection revealed that the susceptibility rate among pregnant women (i.e. rubella virus antibody haemagglutination-inhibition (HAI) assay titres < 10) was 16·5%. As serum rubella antibody HAI titres [ges ] 10 both prevented infection in pregnant women and protected their foetuses, serological testing has been introduced into the routine antenatal services. Pre-existing rubella antibodies were found not to interfere with the immune response to vaccination, so selective immunization was provided to girls approaching puberty and to women of childbearing age. A programme of epidemiological surveillance is being developed to define tactics for the widescale introduction of rubella vaccination.

In Rajahmundry town in India, 234 community cases of jaundice were interviewed for risk factors of viral hepatitis B and tested for markers of hepatitis A–E. About 41% and 1·7% of them were positive for anti-HBc and anti-HCV respectively. Of 83 cases who were tested within 3 months of onset of jaundice, 5 (6%), 11 (13·3%), 1 (1·2%), 5 (6%) and 16 (19·3%) were found to have acute viral hepatitis A–E, respectively. The aetiology of the remaining 60% (50/83) of cases of jaundice could not be established. Thirty-one percent (26/83) were already positive for anti-HBc before they developed jaundice. History of therapeutic injections before the onset of jaundice was significantly higher in cases of hepatitis B (P = 0·01) or B–D (P = 0·04) than in cases of hepatitis A and E together. Other potential risk factors of hepatitis B transmission were equally prevalent in two groups. Subsequent studies showed that the majority of injections given were unnecessary (74%, 95% CI 66–82%) and were administered by both qualified and unqualified doctors.

We describe the epidemiology of the first nationwide outbreak of measles infection in the UK since the implementation of a mass vaccination campaign. Notifications of infectious diseases, interview and postal questionnaire identified 293 clinical cases, 138 of which were confirmed by salivary IgM, measles virus isolation and PCR. Twelve were epidemiologically linked to confirmed cases. The outbreak began in London, after contact with measles infection probably imported from Italy. Measles genotyping determined by sequence analysis confirmed spread to other unimmunized anthroposophic communities in the north, south west and south coast of England. Only two cases had been vaccinated against measles infection, and 90% of cases were aged under 15 years. Measles virus can selectively target non-immune groups in countries with high vaccine uptake and broader herd immunity. Without harmonization of vaccination policies and uniform high coverage across Europe, the importation and spread of measles virus amongst non-immune groups may prevent the elimination of measles.

WHO has adopted a goal of eliminating indigenous measles from the European Region by the year 2007. The strategy focuses on reducing the proportion of susceptible individuals in the population to low levels and maintaining these low levels of susceptibility. Routine vaccination against measles for children aged 13–15 months was introduced in Poland in 1975, and a second dose added in 1991. High coverage (> 95%) is achieved with both doses. In order to assess progress towards measles elimination in Poland, a serological survey was performed to evaluate the impact of vaccination on the susceptibility profile of population. Three thousand residual serum samples from individuals aged 1–30 years were collected from hospitals in six selected voivodeships (administration units) in Poland. These were tested for measles-specific IgG using a commercial ELISA. Overall 4% (120/3000) were negative for measles virus antibody. The highest proportion of negatives (8·2%) occurred among cohorts born 1977–81 – the only cohorts in which susceptibility exceeded the WHO targets. ‘Catch-up’ vaccination strategies should target these cohorts.

Influenza vaccine effect on the occurrence and severity of influenza virus infection in a population residing in nursing homes for the elderly was studied as a cohort study during an influenza A (H3N2) epidemic in Japan. Of 22462 individuals living in 301 welfare nursing homes, 10739 voluntarily received inactivated, sub-unit trivalent influenza vaccine in a programme supported by the Osaka Prefectural Government. There were statistically significantly fewer cases of influenza, hospital admissions due to severe infection, and deaths due to influenza in the vaccinated cohort compared to the unvaccinated controls. No serious adverse reactions to vaccination were recorded. Thus influenza vaccination is effective for preventing influenza disease in persons aged 65 years and over, and should be an integral part of the care of this population residing in nursing homes.

The objective of the study was to assess the prevalence and epidemiology of hepatitis C virus (HCV) infection in pregnant women in the North Thames region, and in the UK in general. Demographic data were linked to neonatal samples prior to anonymization and testing by anti-HCV EIA, and with RIBA 3 confirmation. Risk factors for maternal infection were explored. Area-specific seroprevalence rates were multiplied into population sizes to estimate HCV prevalence in pregnant women in the UK. A total of 241/126009 samples were confirmed anti-HCV positive, and a further 40 were indeterminate, representing a seroprevalence of 0·19–0·22%; 51% of maternal HCV infections were in UK-born women (71% of the population), and 22% in women from continental Europe (5% of the population). Among European-born women, HCV prevalence was associated with birth in continental Europe, partner not being notified at birth registration, partner born in a different region to the mother, and inner city residence. Four of the 241 anti-HCV positive samples (1·7%) were also anti-HIV-1 positive. It was estimated that each year an estimated 1150 out of 730000 pregnancies in the UK would involve a woman infected with HCV (uncertainty range 660–1850), a prevalence of 0·16% (0·09–0·25%). On the basis of reported rates of mother-to-child transmission of HCV, this would represent approximately 70 paediatric HCV infections per year.

A study of 215 Berlin dentists and 108 dental assistants recruited at the 1997 Berlin Dental Society meeting assessed their occupational risk of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, HBV vaccine coverage, and barrier prevention methods used. Among dentists, 7% (95% CI 4–11) and 0·5% (95% CI 0–3) had serological evidence of previous HBV and HCV infection, respectively. Similar figures for dental assistants were 1% (95% CI 0–5) and 0% (95% CI 0–4). Only 74% of dentists and 63% of dental assistants reported HBV vaccination. Approximately half always used gloves, eye glasses, or face masks. HBV unvaccinated dentists whose patients had HBV risk factors had a greater risk of HBV infection; those who always wore face masks were at lower risk (OR 0·2, 95% CI 0·02–0·98). These data indicate that among Berlin dentists, the HCV risk was lower than that of HBV and that face masks may have lowered the risk of HBV. The use of eye glasses or gloves did not appear to lower the risk of HBV acquisition in this population.