In October 1997, an outbreak of meningococcal disease occurred at the University of Southampton. All six cases were first year students living in halls of residence. Microbiological characterization of case and carrier strains, case interviews, and a meningococcal carriage prevalence survey were used to investigate the outbreak. Five cases were due to serogroup C strains, one case was unconfirmed. Serotyping did not distinguish between the strains but gene sequencing permitted identification of two distinct strains in the outbreak. Although none of the cases was known to each other, three had attended the same nightclub one evening 3–4 days before illness. Meningococcal carriage rates in undergraduates were within the range expected (147/587, 25%), but no carriers of outbreak strains were identified in this sample. The findings suggest that in communities with a high degree of social interaction, the introduction of highly virulent meningococcal strains may result in enhanced transmission with clustering of cases.

For many years, invasive meningococcal disease in the Czech Republic occurred sporadically and was caused mainly by meningococci of serogroup B. In 1993, when a new clone (ET-15/37) emerged, the only phenotype found was C:2a:P1.2,5. In 1995, an antigenic variation of the ET-15/37 clone, B:2a:P1.2,5, occurred. The results of immunological surveys conducted in 1989 and 1996 were compared. A significantly higher proportion of 1996 sera than those collected in 1989 showed bactericidal antibodies against N. meningitidis B:2a:P1.2,5 (19·7 vs. 5·1%) and N. meningitidis C:2a:P1.2,5 (15·9 vs. 7·4%), consistent with increased herd immunity due to the spread of the new clone in the Czech Republic. There were differences in the age distribution of the positive sera.

Bacterial and viral salivary antibody testing is proving sensitive and specific, useful for epidemiological studies, and is simple and non-invasive. Salivary serogroup C polysaccharide-specific (SC PS-S) IgA and IgG were determined as a proportion of total salivary IgA and IgG in a group of UK infants who were recipients of a conjugated A/C meningococcal PS vaccine. Geometric mean concentrations (GMCs) of salivary SC PS-S IgG per mg of total IgG (μg/mg) were 0·1 pre-vaccination, rising to 8·2 post first, 16·1 post second and 29·3 post third dose of vaccine. For IgA, the corresponding GMCs in ng/mg were 0·1, 82·8, 69·6 and 91·2. Significant correlations (P<0·0001) were found between serum Ig and salivary IgG SC PS-S antibody for pre-vaccine and 1 month post each dose of vaccine suggesting that SC PS-S IgG in saliva was largely derived from serum. Of the five infants whose sera were analysed for isotype-specific responses, only traces of IgM and IgA were measurable suggesting that the SC PS-S IgA was locally produced. These findings suggests that the widespread use of meningococcal conjugate vaccines is likely to reduce nasopharyngeal carriage and may thereby induce herd immunity in the vaccinated population.

Although diphtheria is declining in Delhi, case fatality rates (CFRs) are rising. In 1997, of 143 clinically suspected cases admitted to the Infectious Diseases Hospital 45 (32%) died. We examined their records to understand the epidemiology and reasons for high CFRs. About 53% of cases were from Delhi; they were not limited to any particular area. All the deaths and 92% (131/143) of cases occurred in children below 10 years of age. Only 12% of cases had received one or more doses of DPT. Muslims contributed significantly more cases than Hindus. CFRs were significantly higher in young (P=0·03) and unvaccinated (P=0·01) children and in those who received antitoxin on the third day of illness or later (P=0·03). The study highlights the importance of improved vaccine coverage and early diagnosis and prompt administration of antitoxin in reducing CFRs for diphtheria in Delhi.

In March 1997, an outbreak of Vero cytotoxin-producing Escherichi coli O157 (VTEC) infection occurred amongst holidaymakers returning from Fuerteventura, Canary Islands. For the investigation, a confirmed case was an individual staying in Fuerteventura during March 1997, with either E. coli O157 VTEC isolated in stool, HUS or serological evidence of recent infection; a probable case was an individual with bloody diarrhoea without laboratory confirmation. Local and Europe-wide active case finding was undertaken through national centres, Salm-Net and the European Programme of Intervention Epidemiology, followed by a case-control study.

Fourteen confirmed and one probable case were identified from England (7), Finland (5), Wales (1), Sweden (1) and Denmark (1) staying in four hotels. Three of the four hotels were supplied with water from a private well which appeared to be the probable vehicle of transmission. The case-control study showed illness was associated with consumption of raw vegetables (OR 8·4, 95% CI 1·5–48·2) which may have been washed in well water. This investigation shows the importance of international collaboration in the detection and investigation of clusters of enteric infection.

A total of 31 strains of Vibrio cholerae O1 (10 from outbreak cases and 7 from surface water) and non-O1 (4 from clinical and 10 from surface water sources) isolated between 1993 and 1997 were examined with respect to presence of cholera enterotoxin (CT) gene by PCR-based assays, resistance to antibiotics, plasmid profiles and random amplified polymorphic DNA (RAPD) analysis. All were resistant to 9 or more of the 17 antibiotics tested. Identical antibiotic resistance patterns of the isolates may indicate that they share a common mode of developing antibiotic resistance. Furthermore, the multiple antibiotic resistance indexing showed that all strains tested originated from high risk contamination. Plasmid profile analysis by agarose gel electrophoresis showed the presence of small plasmids in 12 (7 non-O1 and 5 O1 serotypes) with sizes ranging 1·3–4·6 MDa. The CT gene was detected in all clinical isolates but was present in only 14 (6 O1 serotype and 8 non-O1 serotype) isolates from environmental waters. The genetic relatedness of the clinical and environmental Vibrio cholerae O1 and non-O1 strains was investigated by RAPD fingerprinting with four primers. The four primers generated polymorphisms in all 31 strains of Vibrio cholerae tested, producing bands ranging from <250 to 4500 bp. The RAPD profiles revealed a wide variability and no correlation with the source of isolation. This study provides evidence that Vibrio cholerae O1 and non-O1 have significant public health implications.

We reviewed serological and epidemiological data relating to 1000 consecutive patients from whom specimens were submitted for estimation of bartonella antibodies, using MRL Diagnostics Bartonella IFA IgM and IgG kits. Using 289 control sera, we estimated the specificity of the kits as [ges ]99·0%. Evidence of bartonella infection was found in 16·3% of patients examined. Rates varied by patient group: 20% of patients for whom a diagnosis of cat scratch disease (CSD) was considered probable had evidence of infection, as did 10·4% of patients with ‘possible CSD’, 8·1% of patients with possible bacillary angiomatosis, 18·2% of patients with ‘culture negative’ endocarditis and 17·6% of patients with possible bartonellosis with ophthalmic involvement. An IgM response was seen in 6·6% of patients and IgG in 15·1%. Cases were more frequent among males than females (18·5% vs. 13·9%). Analysis by age showed that although rates of infection were highest in the decades 0–9 years (19·4%) and 10–19 years (20·7%), they fell only slightly in the next three decades. MRL bartonella kits appears to provide a useful and specific approach to the diagnosis of these infections.

The prevalence and characteristics of Escherichia coli and Salmonella spp. as well as counts of E. coli in raw oysters, condiments/spices, and raw oyster cocktails sampled from 72 vendors across Western Trinidad were determined. The microbial quality of the water used in the preparation of raw oysters was also investigated. Of 200 samples each of raw oysters, condiments/spices and oyster cocktails tested, 154 (77·0%), 89 (44·5%) and 154 (77·0%) respectively yielded E. coli. The differences were statistically significant (P=[les ]0·001; χ2=62·91). The mean E. coli count per g in the ready-to-eat oyster cocktail ranged from 1·5×103±2·7×103 in Couva to 8·7×106±4·9×107 in San Fernando. One hundred and forty-six (73·0%) oyster cocktails contaminated with E. coli had counts that exceeded the recommended standard of 16 per g. Of a total of 590 E. coli isolates from various sources tested, 24 (4·1%), 20 (3·4%) and 69 (11·7%) were mucoid, haemolytic and non-sorbitol fermenters respectively. Twelve (2·0%) isolates of E. coli were O157 strains, while 92 (46·0%) of 200 E. coli isolates tested belonged to enteropathogenic serogroups. Ninety (45·0%) and 73 (36·5%) of 200 water samples contained total coliforms and faecal coliforms respectively, with counts that exceeded 2·2 coliforms per 100 ml. Salmonella spp. were isolated from 7 (3·5%), 1 (0·5%) and 2 (1·0%) of 200 samples each, of raw oysters, condiments/spices and oyster cocktails respectively. Oysters pose a health risk to consumers in Trinidad, particularly from colibacillosis and salmonellosis, and the need for increased public awareness of this hazard cannot be over-emphasized.

Four cases of mumps were reported among 180 army recruits who had received MMR vaccine 16 days earlier. Mumps serology, salivary mumps IgM and PCR tests for the SH gene were performed on the 4 cases and on 5 control recruits who remained well. PCR products were sequenced and the sequences compared to those of wild type and vaccine strains of mumps. Further salivary mumps IgM tests were performed on the remaining 171 recruits. Mumps infection was confirmed in the 4 cases but not in the 5 controls. The controls had serological evidence of prior immunity. The SH gene sequence found in the 4 cases was wild type. Saliva tests identified 2 additional recruits with mumps IgM, one of whom had presented with suspected mumps 2 days before the MMR vaccine was given. Thus 6 (5 symptomatic and 1 asymptomatic) cases of mumps in army recruits recently receiving MMR vaccine were not due to the vaccine but to coincidental infection with wild-type mumps virus. The probable index case was revealed by salivary mumps IgM tests. This study highlights the importance of appropriate investigation of illness associated with MMR vaccination.

In a 5-year retrospective survey of respiratory syncytial virus (RSV) infections among hospitalized children, 1340 cases were identified of which, 98·4% were children <5 years old with a male:female ratio of 1·5:1. Most cases occurred from April to September showing a significant positive correlation with temperature and relative humidity. Community-acquired infections accounted for 92·5% of the cases with a mean hospital stay of 5 days. The estimated annual incidence of RSV infection requiring hospitalization was 2·5/1000 children <5 years old with a mortality of 0·15% among hospitalized cases. On average, 248 children were admitted each year to the 1400-bed acute regional hospital accounting for an expenditure of HK $1.94 (∼US $0.25) million for hospitalization costs which equates to an annual cost in excess of HK $6.67 (∼US $0.86) million for the whole of Hong Kong. An RSV vaccine should be a priority.

A two-dose mass vaccination programme with a combined vaccine against measles, mumps and rubella (MMR) was adopted in the Netherlands in 1987, replacing the selective schoolgirl vaccination strategy introduced in 1974. To obtain insight into the effect of mass vaccination and the population's immunity, the antibody levels against rubella were studied in the general Dutch population and in religious groups refusing vaccination. In the national sample, we observed a high prevalence (96·5%) for rubella antibodies in vaccinated cohorts as well as in the older unvaccinated cohorts. No indications of rapidly waning immunity after vaccination were found. There are indications of low virus circulation in the last few years. The very high seroprevalence in women at childbearing age is consistent with the few reported cases of congenital rubella syndrome (CRS) at present. However, individuals in the age group of 1–9 years who are not vaccinated for religious or other reasons have a considerably lower seroprevalence and thus there is a potential risk of a CRS outbreak in the future.

Four years after the occurrence of an outbreak of hepatitis B and HIV infection among injecting drug user inmates at Her Majesty's Prison Glenochil in Scotland, a study design was developed to complete the epidemiological account of the HIV outbreak. Our aim was to identify potential cases of (1) HIV transmission not diagnosed during the original outbreak investigation and (2) the source(s) of the outbreak. Scotland's HIV positive case register was searched for matches to a soundexed list of 636 Glenochil inmates imprisoned during January–June 1993. Eight HIV infections that may have been acquired in Glenochil and four possible sources of the outbreak were identified. The second stage of follow-up – molecular epidemiological techniques used on stored sera samples from identified individuals – is described in the companion paper. Without breach of medical or prisoner confidentiality, indirect and anonymous follow-up has proved possible for the Glenochil inmates.

In a molecular investigation into the outbreak of HIV in Glenochil during the first 6 months of 1993, we previously demonstrated that 13 out of the 14 HIV positive inmates were infected with a virtually identical strain, and discounted 2 others as potential sources. Here we investigate a further 8 potential contacts and 4 potential sources which were identified in the companion paper [1]. We were able to examine viral sequence from all but one of these 12 and results have revealed them to be distinct both from each other and the original 14. Thus, despite an intensive follow-up investigation, we have been unable to identify any further HIV infections that might have been part of the 1993 outbreak. It is possible that persons who were infected at that time remain undetected; however this and the companion report strongly suggest that if this were the case the likely numbers would be few.

Ocular disease is the commonest disabling consequence of toxoplasma infection. Incidence and lifetime risk of ocular symptoms were determined by ascertaining affected patients in a population-based, active reporting study involving ophthalmologists serving a population of 7·4 million. Eighty-seven symptomatic episodes were attributed to toxoplasma infection. Bilateral visual acuity of 6/12 or less was found in seven episodes (8%) and was likely to have been transient in most cases. Black people born in West Africa had a 100-fold higher incidence of symptoms than white people born in Britain. Only two patients reported symptoms before 10 years of age. The estimated lifetime risk of symptoms in British born individuals (52% of all episodes) was 18/100000 (95% confidence interval: 10·8–25·2). The low risk and mild symptoms in an unscreened British population indicate limited potential benefits of prenatal or postnatal screening. The late age at presentation suggests a mixed aetiology of postnatally acquired and congenital infection for which primary prevention may be appropriate, particularly among West Africans.

This study was designed to determine the prevalence of Escherichia coli O157:H7 infection of beef calves at weaning, prior to arrival at the feedlot or mixing with cattle from other sources. Fifteen range cow-calf herds, which weaned calves in October and November, were sampled in Kansas, Missouri, Montana, Nebraska and South Dakota. Faecal culture for E. coli O157:H7 was performed and anti-O157 serum antibody titres were determined by blocking ELISA. Thirteen of the 15 herds (87%) were found to have at least one positive isolation of E. coli O157:H7 in faecal samples. Within positive herds, prevalence ranged from 1·7–20·0%, with an average of 7·4±6·2% s.d. of individual animals shedding E. coli O157:H7 in faeces. All herds had high prevalence of anti-O157 antibodies, ranging 63–100% of individuals within herds seropositive. This study indicates that E. coli O157:H7 infection before weaning, prior to entry into feedlots, is widespread. Furthermore, serologic evidence suggests that most calves (83%) and all herds (100%) have been exposed to E. coli O157.

Pulsed-field gel electrophoresis (PFGE) pattern analysis with XbaI restriction enzyme was used to study the genetic heterogeneity of 88 atypical Aeromonas salmonicida strains which were earlier or during this study characterized phenotypically, by ribotyping (ClaI/PstI) and by plasmid profile analysis. The strains of certain ribotypes were also analysed by digestion with SpeI. The strains represented different geographic locations: Finland (72 strains), Iceland (5 strains), Norway (5 strains), Sweden (4 strains) and Denmark (2 strains), and they were from 17 fish species during 1981–97. Thirty-one PFGE genotypes found among these strains correlated well with the ribotypes, and in most cases PFGE pattern analysis subdivided ribotypes into several PFGE genotypes, and further within a PFGE genotype into subtypes. XbaI and SpeI digests produced concordant results. In most cases, PFGE patterns of strains with the same ribotype shared many fragments, suggesting genetic relatedness. PFGE patterns of most Norwegian and Icelandic strains isolated during an approximately 10-year period had the same ribotype and their PFGE patterns shared most fragments, suggesting close genetic relatedness. Moreover, atypical strains of ribotypes B/B and H/H isolated from the same Finnish fish farms had closely related patterns suggesting genetic stability and persistence of these genotypes. Genotype 29 of Achromogenic strains was strongly associated with disease of Finnish arctic char and grayling. PFGE was shown to be a distinguishing method to study the genetic heterogeneity of atypical A. salmonicida. This method is applicable to studies of the epidemiology of these infections.

Analysis of the transmission dynamics of Cowdria ruminantium, the tick-borne rickettsial agent of heartwater in ruminants, requires accurate measures of infection in vector populations. To obtain these, Amblyomma hebraeum ticks were collected at two heartwater-endemic locations in the lowveld and highveld regions of Zimbabwe and assessed for C. ruminantium infection with specific polymerase chain reaction (PCR) and DNA probe detection assays. At the lowveld site, 11·2% (50/446) of adult ticks and 8·5% (23/271) of nymphs carried C. ruminantium, as detected by PCR. At the highveld site, the prevalence of infection in adult ticks was 10·2% (40/392). DNA probe analysis revealed that most infections at both sites were of low intensity; only 9% and 23% of all nymph and adult tick infections, respectively, were greater than 70000 organisms, the detection limit of the DNA probe. However, the majority (70%) of probe- detectable adult tick infections were high, between 107 and 109 organisms/tick, while those within nymphs were lower, between 105 and 106 organisms/tick.

Pulsed-field gel electrophoresis (PFGE) was used to investigate the epidemiology of streptococcal mastitis in dairy cattle. The most prevalent streptococcal species, Streptococcus uberis (60–80% of streptococcal isolates), was highly heterogeneous, with different cows only rarely sharing the same pulsotype. S. agalactiae was rarely encountered, however all eight isolates from one farm generated identical PFGE profiles, which differed from those of all other isolates examined, confirming cow-to-cow transmission. Fifty-two isolates of S. dysgalactiae from 27 cows on 5 farms generated 6 different profiles. However, on individual farms, only one or two pulsotypes usually predominated. This species is generally regarded as an environmental pathogen but our data suggest that cow-to-cow transmission of S. dysgalactiae may occur. In spite of the variation in PFGE profiles of isolates from different cows, persistent infections in individual cows were usually caused by the same pulsotype of S. uberis or S. dysgalactiae.

A previous study on N gene variation of rabies viruses circulating in Ontario red foxes identified four viral variants. This study confirms the geographical localization of these variants and extends the analysis to the less conserved G gene of these viruses. A greater number of regionally localized variants was revealed and their phylogenetic relationships have been examined. Ongoing surveillance on recent disease outbreaks revealed that variants do not always persist in specific areas. The distribution of these variants did however appear to be influenced by topographical features of the study area likely to affect host animal movements and contacts. The majority of G gene base changes were synonymous and limited glycoprotein sequence variation predominantly to the C-terminal transmembrane and endo-domains. These data are most readily explained by random appearance of genetic viral variants followed by their spread throughout sub-populations of the fox host according to the easiest routes of transmission.

African horse sickness (AHS) was diagnosed for the first time in southern Portugal in autumn 1989, following outbreaks in Spain. AHS virus presence was confirmed by virus isolation and serotyping. An eradication campaign with four sanitary zones was set up by Central Veterinary Services in close collaboration with private organizations. Vaccination began on 6 October. In February 1990, vaccination was extended to all Portuguese equines (170000 animals). There were 137 outbreaks on 104 farms: 206 of the equidae present died (16%) or were slaughtered (14%); 81·5% were horses, 10·7% were donkeys and 7·8% were mules. Clinical AHS occurred more frequently in horses than donkeys and mules. In the vaccinated population, 82 animals (62·2% horses and 37·8% mules and donkeys), died or were slaughtered due to suspected or confirmed AHS. One year after ending vaccination, December 1991, Portugal was declared free of AHS. Cost of eradication was US$1955513 (US$11·5/Portuguese equine).