Although campylobacter has been the most commonly recognized bacterial cause of gastro-intestinal infection in England and Wales since 1981, there are few reported campylobacter outbreaks. Of the 2374 general outbreaks of infectious intestinal disease reported to CDSC between 1995 and 1999, for which an aetiological agent was identified, campylobacter accounted for only 50 (2%). Foodborne transmission was identified in 35 outbreaks and the majority took place in commercial catering establishments; waterborne transmission was responsible for a further four outbreaks. Isolates of Campylobacter jejuni were referred for typing from 25 outbreaks. In 13 outbreaks all isolates were the same subtype, as defined by serotype and phage type, while in the remainder more than one campylobacter subtype was involved.

Some years ago, an increase in the number of sporadic cases and outbreaks of salmonellosis due to S. enterica serovar Bovismorbificans was observed in several European countries including Finland, Sweden, England/Wales, Austria, and Germany. In order to understand the recent spread of this serovar and to trace the route of infection back to its source, it was considered necessary to subtype S. Bovismorbificans isolates. Using phage typing (newly described here) and molecular fingerprinting (PFGE-pattern, plasmid profiles and ribotype) the isolates of European origin could be subtyped and compared to S. Bovismorbificans isolates that originated in overseas countries such as Australia, Thailand, India, etc. where this serovar was isolated more frequently. Significant clonal diversity was identified but some of the clonal types of S. Bovismorbificans dominated the epidemics and single cases in Europe as well as in overseas countries. The clonal identity among these isolates indicates an international distribution, new sources of infection, and highlights the urgent requirement for standardized laboratory based surveillance networks (e.g. Enter-Net). Moreover, it is suggested that strains of S. Bovismorbificans will continue to be of concern in public health and that phage typing together with PFGE typing can be applied as reliable and rapid tools for their future monitoring.

An epidemiological study was carried out to find out the aetiological agent for diarrhoeal disorders in the cyclone and flood affected areas of Orissa, India. Rectal swabs collected from 107 hospitalized diarrhoea patients were bacteriologically analysed to isolate and identify the various enteropathogens. Detection of toxic genes among E. coli and V. cholerae was carried out by polymerase chain reaction (PCR) assay. Of the 107 rectal swabs analysed, 72·3% were positive for V. cholerae O1 Ogawa, 7·2% for V. cholerae O139, 1·2% for E. coli (EAggEC) and 1·2% for Shigella flexneri type 6. Using multiplex PCR assay it was found that all V. cholerae isolates were ctxA positive and El Tor biotype. Strains of V. cholerae O1 were observed to be resistant to nalidixic acid, furazolidone, streptomycin, co-trimoxazole and ampicillin. Except for nalidixic acid, the resistance pattern for O139 was identical to that of O1 strains. Representative strains of V. cholerae were further characterized by randomly amplified polymorphic DNA (RAPD) analysis and ribotyping. Both O1 and O139 V. cholerae strains exhibited the R3 pattern of ribotype and belonged to a similar pattern of RAPD compared with that of Calcutta strains. Early bacteriological and epidemiological investigations have revealed the dominance of V. cholerae O1 among the hospitalized patients in cyclone affected areas of Orissa. Drinking water scarcity and poor sanitation were thought to be responsible for these diarrhoeal outbreaks. Timely reporting and implementation of appropriate control measures could contain a vital epidemic in this area.

A review of the epidemiology of invasive pneumococcal disease in Scotland was carried out using data from laboratory-based systems during the period 1988–99. This comprised 5456 (90·8%) isolates of Streptococcus pneumoniae from blood, 467 (7·8%) from cerebrospinal fluid (CSF) and 84 (1·4%) from other sterile sites. The mean annual incidence of invasive disease was 9·8/105 population (9·0/105 for bacteraemia and 0·8/105 for meningitis). Invasive disease was highest in children <2 years of age and in the elderly [ges ]65 years (44·9/105 and 28·4/105 population in these age groups respectively). The highest incidence of pneumococcal meningitis, 11·8/105 persons occurred in children <2 years of age. Males had a higher incidence of pneumococcal bacteraemia and meningitis than females (male[ratio ]female = 1·2[ratio ]1 for bacteraemia (RR = 1·17, 95% CI 1·11, 1·24) and 1·5[ratio ]1 for meningitis (RR = 1·41, 95% CI 1·18, 1·70)). Pneumococcal disease was highest in winter periods and coincided with influenza activity. The proportion of penicillin and erythromycin non-susceptible isolates increased from 4·2% in 1992 to 12·6% in 1999 and from 5·6% in 1994 to 16·3% in 1999 respectively. Our data confirm the substantial and increasing disease burden from pneumococcal disease and rise in prevalence of antibiotic non-susceptibility among pneumococci in Scotland. Continued surveillance of groups at increased risk for pneumococcal disease and the antibiotic susceptibility and serotype distribution of isolates are important to develop appropriate policies for the prevention of pneumococcal disease in Scotland.

We examined the serological characteristics of 774 invasive meningococcal isolates collected through an active laboratory-based surveillance system in Scotland from 1994 to 1999. Of these, 72–73% of isolates were tested for susceptibility to several antimicrobial agents. Meningococci with high-level resistance to sulphadiazine had a prevalence of 10% and incidence of 0·22 per 100000 population. High-level resistance to penicillin and other antibiotics was not detected. The prevalence of moderate penicillin resistant meningococci was 8·3%. There was no increase in moderate penicillin resistant meningococcal isolates during the study period, but there were temporal and geographic variations. The estimated incidence of moderate penicillin resistant meningococci was 0·15 per 100000 population. High and low incidence of moderate penicillin resistant meningococci appeared to correlate with the number of doses of penicillin prescribed in some geographic locations. The majority of moderate penicillin resistant isolates belonged to serogroups B (52·2%) and C (39·2%). However, the prevalence of moderate penicillin resistance in serogroup W135 was substantially higher (51·7%) than serogroups B (7·8%) and C (7·6%). Serogroup W135 accounted for a higher proportion of moderate penicillin resistance (8·7%) than disease (1%). There was no predominant penicillin resistant serotype/subtype within any serogroup. Constant surveillance is necessary to monitor the emergence and spread of resistance and to guide appropriate public health interventions in preventing drug resistant meningococci.

MLST typing of Neisseria meningitidis directly from clinical material was introduced in the National Reference Laboratory for Meningococcal Infections in Prague. Four cerebrospinal fluid samples were obtained from patients with suspected meningococcal invasive disease. In all samples, all classical laboratory methods gave negative results and the only positive method was PCR, which revealed Neisseria meningitidis group C (two specimens) and group B (two specimens), respectively. MLST performed directly from cerebrospinal fluid revealed that the strains causing the two group C infections were of sequence type (ST) 11, while the two group B infections were characterized as ST-32 and ST-33 respectively. Multi-locus sequence typing of meningococci directly from clinical material offers the opportunity to improve further the surveillance of meningococcal disease and has now been introduced into the routine portfolio of tests employed at the national reference laboratory of the Czech Republic.

In Australia, notification of pertussis cases in older children or adults has increased significantly in recent years. In most cases, laboratory diagnosis is based only on a positive serological test for IgA antibody against whole cell Bordetella pertussis. During a 3-month period, 318 consecutive sera submitted for diagnosis of pertussis were tested for IgA antibody against whole cell (WC) sonicated B. pertussis, pertussis toxin (PT), filamentous haemagglutinin (FHA) and pertactin (PRN). Results of one or more of these tests were positive in sera from 175 subjects and clinical information was obtained by telephone interview from 90 subjects. Using a clinical case definition as the reference standard, the sensitivities of the four IgA assays were variable but quite low (24–64%), but the specificities were high (93–98%). For diagnosis of pertussis in subjects with a compatible clinical illness, these and other findings support the use of serological testing for IgA antibody.

Reports of neonatal tetanus (NT) disease, common in developing countries, often suffers from gender bias because male infants are brought to health facilities while females are attended at home. Using existing health data we applied reasonable assumptions to estimate the true incidence of NT economically. To adjust for gender disparities in national reporting, we ignored the number of female NT cases and doubled the number for males. Governorates with similar demographic risk profiles for NT were assigned to one of six groups. The highest incidence rate within the group was determined and applied to the number of live births represented by the group. Other internal data comparisons were done to support our estimate that the male[ratio ]female ratio of NT incidence was far less than the reported 4·12[ratio ]1. In 1991, the male[ratio ]female ratio of NT cases was 4·12[ratio ]1. Decreasing the male[ratio ]female ratio to 1[ratio ]1 decreased sensitivity to a 62% estimate. Further adjusting for assumed under-reporting by governorates based on population profiles yielded a reporting sensitivity of 40%. Estimated male and female age-specific NT mortality rates from available data supported the assumption that NT mortality ratios are less than 4·12[ratio ]1. This report, therefore, describes a unique, economical method to estimate the incidence of a disease assumed to be affected by gender biases in the reporting system. The method relies on two assumptions: that the true NT male[ratio ]female ratio is close to 1[ratio ]1 and that populations with similar demographics within a country should have similar incidence rates of NT.

The study used DNA fingerprint typing (spoligotyping and Heminested-Inverse-PCR) of Mycobacterium tuberculosis from all culture-confirmed inner London patients over a 12-month period to describe transmission. The methodology was evaluated by comparison with standard IS6110 typing and by examining its ability to identify known household clusters of cases. Isolates sharing indistinguishable typing patterns using both techniques were defined as clustered. Clusters were investigated to identify epidemiological links. The methodology showed good discriminatory power and identified known household clusters of cases. Of 694 culture-confirmed cases, 563 (81%) were typed. Eleven (2%) were due to laboratory cross-contamination and were excluded. Of the remaining 552 isolates 148 (27%) were clustered. Multivariate analysis indicated that clustering was more common in those with pulmonary smear positive disease (P<0·02); those born in the United Kingdom (P<0·0003) and in patients living in south London (P = 0·02). There was also a trend towards clustering being more common in those not known to have HIV infection (P = 0·051). The results suggest that in inner London, recent local transmission makes an important contribution to notification rates.

For the prevention of pertussis and invasive Haemophilus influenzae type b (Hib) infections, each with a peak for mortality and serious complications in the first year of life, early vaccination is important and needs adequate monitoring. In a 1999 national coverage survey the timing of uptake of these vaccines in German children was therefore assessed conventionally at defined age thresholds and with a new adaptation of the Kaplan–Meier (KM) method estimating immunization uptake over time by 1 minus the survival function s(t). Only 6% and 9% of children were vaccinated against pertussis and Hib in accordance with the national recommended primary vaccination schedule. Coverage levels for the primary vaccination course of 50% and 90% were attained for pertussis after 6·6 and 16·3 months respectively and for Hib after 7·0 and 24·3 months. These estimates were only possible with the KM method which proved useful to monitor vaccination programmes and will allow the comparison of vaccination uptake in different populations.

We study the statistical inference from data on transmission obtained from one-to-one experiments, and compare two algorithms by which the reproduction ratio can be quantified. The first algorithm, the transient state (TS) algorithm, takes the time course of the epidemic into account. The second algorithm, the final size (FS) algorithm, does not take time into account but is based on the assumption that the epidemic process has ended before the experiment is stopped. The FS algorithm is a limiting case of the TS algorithm for the situation where time tends to infinity. So far quantification of transmission has relied almost exclusively on the FS algorithm, even if the TS algorithm would have been more appropriate. Its practical use, however, is limited to experiments with only a few animals. Here, we quantify the error made when the FS algorithm is applied to data of one-to-one experiments not having reached the final size. We conclude that given the chosen tests, the FS algorithm underestimates the reproduction ratio R0, is liberal when testing H0[ratio ]R0[ges ]1 against H1[ratio ]R0<1, is conservative when testing H0[ratio ]R0[les ]1 against H1[ratio ]R0>1 and calculates the same probability as the TS algorithm when testing H0[ratio ]R0-control = R0-treatment against H1[ratio ]R0-control>R0-treatment. We show how the power of the test depends on the duration of the experiments and on the number of replicates. The methods are illustrated by an application to porcine reproductive and respiratory syndrome virus (PRRSV).

Influenza immunization rates among young asthmatics remain unsatisfactory due to persistent concern about the impact of influenza and the benefits of the vaccine. We assessed the effectiveness of the conventional inactivated trivalent sub-unit influenza vaccine in reducing acute respiratory disease in asthmatic children. We conducted a two-season retrospective cohort study covering the 1995–6 and 1996–7 influenza outbreaks in 22 computerized primary care practices in the Netherlands. In total, 349 patients aged between 0 and 12 years meeting clinical asthma-criteria were included; 14 children were lost to follow-up in the second season. The occurrence of physician-diagnosed acute respiratory disease episodes including influenza-like illness, pneumonia, bronchitis, bronchiolitis, asthma exacerbation and acute otitis media in vaccinated and unvaccinated children were compared after adjustments for age, prior health care and medication use. The occurrence of acute respiratory disease in unvaccinated children was 28% and 24% in the 1995–6 and 1996–7 season, respectively, and was highest in children under 6 years of age (43%). The overall pooled clinical vaccine effectiveness was 27% (95% confidence interval −7 to 51%, P = 0·11) after adjustments. A statistically higher vaccine protectiveness of 55% (95% CI 20–75%, P = 0·01) was observed among asthmatics under 6 years of age compared with −5% in older children (95% CI −81 to 39%). The occurrence of acute respiratory disease among asthmatic children during influenza epidemics is very high, notably in the youngest. Influenza vaccination may reduce morbidity in asthmatic infants and pre-school children. However, larger, preferably experimental, studies are needed to establish the benefits of vaccination, notably in older asthmatic children.

Dengue and Japanese encephalitis flaviviruses cause severe disease and are hyperendemic in southern Vietnam. This study assesses associations between sociodemographic factors and flavivirus seroprevalence in this region. Sera were collected from 308 community and hospital-based subjects between April 1996 and August 1997 and tested with an indirect ELISA. The factors associated with seroprevalence were assessed using multivariate logistic regression. In this first report of adjusted prevalence odds ratios (POR) for flavivirus infection in Vietnam, seropositivity was associated with increasing age in children (multiple regression coefficients for a child compared to an adult =−4·975 and for age in children = 0·354) and residence in the city compared to surrounding rural districts. The association with age indicates that subjects were most likely to have acquired infection in early childhood. This is key to the design of Vietnamese health education and immunization programmes.

The aim was to determine the prevalence of HIV infection and risk factors for HIV infection in various population subgroups in Ethiopia. Serum panels from blood donors (n = 2610), from various population subgroups in Ethiopia were tested for anti-HIV-1/2 by ELISA. All ELISA repeatedly reactive samples were subjected for confirmation by immunoblot (IB) and anti-HIV-1 and anti-HIV-2 specific ELISAs. 155/2610 (5·9%) blood donors were HIV-1 infected. Of pregnant women, 84/797 (10·5%) were HIV-1 infected, and 1/797 (0·1%) was HIV-2 infected. 1/240 (0·4%) individuals from the rural population were HIV-1 infected. 198/480 (41·3%) female attendees, and 106/419 (25·3%) male attendees at sexual transmitted disease (STD) clinics were HIV-1 infected. One (0·2%) male, and 2 (0·4%) female STD patients were infected with both HIV-1 and HIV-2. It was concluded that the prevalence of HIV-1 infection varied from 0·4% among urban residents to 25·3–41·3% among STD attendees. There is a low prevalence of HIV-2 present in Ethiopian subjects. Risky sexual behaviour is significantly associated with HIV-infection in Ethiopia.

A mathematical model that takes transmission by sexual contact and vertical transmission into account was employed to describe the transmission dynamics of hepatitis B virus (HBV) and vaccination against it. The model is an extension of a model by Williams et al. (Epidemiol Infect 1996; 116; 71–89) in that it takes immigration of hepatitis B carriers from countries with higher prevalence into account. Model parameters were estimated from data from The Netherlands where available. The main results were that, given the estimates for the parameters describing sexual behaviour in The Netherlands, the basic reproduction number R0 is smaller than 1 in the heterosexual population. As a consequence, the immigration of carriers into the population largely determines the prevalence of HBV carriage and therefore limits the possible success of universal vaccination. Taking into account the prevalence of hepatitis B carriage among immigrants and an age-dependent probability of becoming a carrier after infection, we estimate that a fraction of between 5 and 10% of carrier states could be prevented by universal vaccination.

A significant challenge in the epidemiological investigation of recreational waterborne disease is the establishment of a definite association between exposure to a contaminated water and infection. An increase in specific antibodies as a result of infection is a potent measure of disease exposure and its determination would enhance epidemiological studies of waterborne diseases. We report on the automated detection of HAV antibodies in crevicular fluid and its use in a field study. The method is easy to use, non-invasive, could be applied to volunteers of all ages and is comparable in sensitivity to serological procedures. Application to an epidemiological study of water recreationalists demonstrated that surfers were three times more likely to be immune to hepatitis A virus than either wind-surfers or a control group without recreational water contact.

European common voles (Microtus arvalis), captured in Belgium in 1999, were proven by molecular as well as by serological techniques to be infected with Tula hantavirus (TULV). This is the first evidence for the presence of TULV in this country. No indication of spill-over infections of Puumala virus, known to be highly endemic among bank voles (Clethrionomys glareolus) within the same geographical regions as the trapped TULV-infected common voles, was observed. Together with previous reports on the circulation of TULV in eastern/central Europe, this finding suggests a more wide-spread circulation of this hantavirus serotype throughout the continent.

Sentinel herds of large ruminants were established at five centres in Yunnan Province, Peoples Republic of China, between 1995 and 1997. The application of a sensitive antigen capture ELISA to facilitate virus isolation procedures led to the isolation of 108 strains of bluetongue (BLU) virus. Serotypes isolated included types 1, 2, 3, 4, 9, 11, 12, 15, 16, 21 and 23. Virus transmission occurred over a period of 1–3 months at each of the four positive sites, giving an overall BLU virus transmission period for the province of 5 months, from early June to early November. The greatest level of transmission took place in July and August. The duration of viraemia in individual animals varied from 1 to 7 weeks, with a mean calculated for each serotype between 6 and 20 days. The study represents the first detailed investigation of the epidemiology of BLU in China utilizing sentinel herds.

African horse sickness (AHS) and equine encephalosis (EE) viruses are endemic to southern Africa. AHS virus causes severe epidemics when introduced to naive equine populations, resulting in severe restrictions on the movement of equines between AHS-positive and negative countries. Recent zoning of South Africa has created an AHS-free zone to facilitate equine movement, but the transmission dynamics of these viruses are not fully understood. Here, we present further analyses of serosurveys of donkeys in South Africa conducted in 1983–5 and in 1993–5. Age-prevalence data are used to derive estimates of the force of infection, λ. For both viruses, λ was highest in the northeastern part of the country and declined towards the southwest. In most of the country, EE virus had a higher transmission rate than AHS. The force of infection increased for EE virus between 1985 and 1993, but decreased for AHS virus. Both viruses showed high levels of variation in transmission between districts within the same province, particularly in areas of intermediate transmission. These data emphasize the focal nature of these viruses, and indicate areas where further data will assist in understanding the geographical variation in transmission.

Isotype specific ELISAs to detect antibodies against swine vesicular disease, which may help to estimate the moment of infection, were developed and validated on sera from pigs experimentally infected with four different isolates of swine vesicular disease virus. Virus specific IgM antibodies could be detected from days 3–49 and occasionally up to day 91 after infection. IgG1 antibodies were first detected at day 8 and IgG2 at day 11. IgA antibodies coincided with IgG1 antibodies, but antibody titres varied widely. From the results obtained with the sera from the experimentally infected pigs, we calculated the day at which 50% of the pigs had become positive (D50). A D50 of 5, 4, 12, 12 and 24 days was calculated, respectively, for the appearance of antibodies in the virus neutralization test, the IgM, total IgG, IgG1 and IgG2 ELISA. A D50 of 49 days was calculated for the disappearance of IgM antibodies. The isotype specific ELISAs proved to be valuable tools to study the epidemiology of the disease.