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.

An immunofluorescence test for detecting parvovirus B19 IgG was developed by infecting insect cells with recombinant baculovirus expressing the capsid protein VP1. The test was used to study the prevalence of antibodies in 725 healthy children and young adults living in Santiago, Chile. In total, 248 sera were taken in 1990 and 477 in 1996. The seroprevalence was low in children less than 5 years old (3% in 1990 and 21% in 1996). It rose during school age to a prevalence around 50%, reaching 60% in young adults. No differences were found between genders. There was a statistically significant higher seroprevalence in the low socio-economic status group in 1990 samples, but this was not observed in 1996. The higher prevalence observed in children less than 5 years of age in 1996 compared with 1990 could be explained by the occurrence of intervening epidemics of parvovirus B19 infection.

The prevalence of active infection with Helicobacter pylori in the general population of England and Wales was estimated using high reactivity for specific IgG in serum ELISA as a marker. A total of 10118 anonymized residues of serum samples collected in 1986 and 1996 from persons aged 1–84 years were used. Estimated prevalence of active infection varied by region and was highest in London. Prevalence was related to decade of birth and increased from 4·3% in those born during the 1980s to 30% in those born before 1940. An estimated total of 7·5 million people living in England and Wales have an active infection and analysis by decade of birth showed no significant difference between samples collected in 1986 and 1996. These data suggest H. pylori infection is becoming less common, is acquired at an early age and is unlikely to be resolved unless suitable antimicrobial treatment is sought.

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.

Tattoos have been shown to be associated with transfusion-transmitted diseases (TTDs), particularly hepatitis B virus (HBV) and hepatitis C virus (HCV) infections. Very little is known about the association between different categories of tattoos and TTDs. In a cross-sectional study in Brazil, we studied 182 individuals with tattoos and assessed the odds of testing positive for a TTD according to tattoo type, number, design and performance conditions. Major findings were significant associations between an increasing number of tattoos and HBV infection (odds ratio (OR) of 2·04 for two tattoos and 3·48 for [ges ] 3 tattoos), having a non-professional tattoo and testing positive for at least one TTD (OR = 3·25), and having [ges ] 3 tattoos and testing positive for at least one TTD (OR = 2·98). We suggest that non-professional tattoos and number of tattoos should be assessed as potential deferral criteria in screening blood donors.

Few studies have assessed risk factors for sporadic cryptosporidiosis in industrialized countries, even though it may be numerically more common than outbreaks of disease. We carried out case-control studies assessing risk factors for sporadic disease in Melbourne and Adelaide, which have water supplies from different ends of the raw water spectrum. In addition to examining drinking water, we assessed several other exposures. 201 cases and 795 controls were recruited for Melbourne and 134 cases and 536 controls were recruited for Adelaide. Risk factors were similar for the two cities, with swimming in public pools and contact with a person with diarrhoea being most important. The consumption of plain tap water was not found to be associated with disease. This study emphasizes the need for regular public health messages to the public and swimming pool managers in an attempt to prevent sporadic cryptosporidiosis, as well as outbreaks of disease.

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.

In a cross-sectional survey of 226 HIV-infected men, we examined the occurrence of diarrhoea and its relationship to drinking water consumption patterns, risk behaviours, immune status and medication use. Diarrhoea was reported by 47% of the respondents. Neither drinking boiled nor filtered water was significantly associated with diarrhoea (OR = 0·5 [0·2, 1·6], 1·2 [0·6, 2·5] respectively), whereas those that drank bottled water were at risk for diarrhoea (OR = 3·0 [1·1, 7·8]). Overall, 47% always or often used at least one water treatment. Of the 37% who were very concerned about drinking water, 62% had diarrhoea, 70% always or often used at least one water treatment. An increase in CD4 count was protective only for those with a low risk of diarrhoea associated with medication (OR = 0·6 [0·5, 0·9]). A 30% attributable risk to diarrhoea was estimated for those with high medication risk compared to those with low medication risk. The significant association between concern with drinking water and diarrhoea as well as between concern with drinking water and water treatment suggests awareness that drinking water is a potential transmission pathway for diarrhoeal disease. At the same time we found that a significant portion of diarrhoea was associated with other sources not related to drinking water such as medication usage.

We took the opportunity provided by a large outbreak of cryptosporidiosis in the North West of England to investigate the potential impact of recall bias on strength of association and on estimates of outbreak size. We conducted a community-based survey of 4 towns within the outbreak area and 4 control towns. A postal questionnaire was sent to 120 homes, chosen at random from the local telephone directory, in each of the 8 towns. Although not statistically significant, the prevalence of self-reported diarrhoeal disease was marginally higher in the control towns than in the outbreak towns. There was a very strong association between self-reported diarrhoea and drinking water consumption in both control and outbreak areas. The impact of recall bias in outbreak investigations is much greater than previously thought. Identification of the cause of outbreaks should not be based solely on case-control studies conducted after the press has reported the outbreak. Such evidence is likely to be unreliable and give falsely significant associations between water consumption and disease.

Hepatitis B carriers who acquired the infection perinatally die from hepatocellular carcinoma (HCC) and cirrhosis at high rates. Published cohort studies are largely limited to males and are too small to estimate the age-specific risk of death. We therefore used routinely collected Hong Kong data to estimate the risks. Deaths were partitioned between carriers and non-carriers, then current life table calculations determined life expectancy and probability of dying from HCC or cirrhosis. HCC is the dominant cause of death for male carriers in middle adulthood with a lifetime risk of 27% for HCC compared to 4% for females. Predicted life expectancy is 72 years for male carriers, compared to 79 years for non-carriers. Female carriers have a life expectancy of 81 years and non-carriers 83 years. This model probably applies to all southern Chinese populations and emigrants with similar life history, and other populations that acquired infection early in life.

During the period 1974–91 large numbers of Southeast Asian immigrants and refugees were resettled in Western countries, including Australia. Health screening during this period demonstrated that intestinal parasite infections were common. A cross-sectional survey of 95 Laotian settlers who arrived in Australia on average 12 years prior to the study was conducted to determine if chronic intestinal parasite infections were prevalent in this group. Twenty-three participants had positive Strongyloides stercoralis test results (22 with positive serology, including 1 with S. stercoralis larvae detected in faeces and another with larvae and equivocal serology). Of these 23 participants, 18 (78%) had an elevated eosinophil count. Two patients had eggs of Opisthorchis spp. identified by faecal microscopy. The detection of chronic strongyloidiasis in Laotian settlers is a concern because of the potential serious morbidity associated with this pathogen.

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.

A survey of the coverage, distribution and the factors associated with use of influenza and pneumococcal vaccines among general practitioners (GPs) in primary care and in hospital settings was carried out in 53 general practices in Scotland taking part in the ‘Continuous Morbidity Recording’ (CMR) programme. The annual vaccine distribution increased substantially among 53 general practices from 1993 to 1999 and in Scotland as a whole from 1984 to 1999. From the questionnaire, overall coverage was 43% (95% CI 38–48) for influenza vaccine in the 2000–1 season and 13% (95% CI 9–16) for pneumococcal vaccine in the last 5 year period, in high-risk patients recommended for these vaccines by the Department of Health (DoH). Influenza vaccine coverage was highest in the elderly (65 years of age and above) at 62% (95% CI 59–74). Although pneumococcal vaccination is not currently recommended for all elderly, coverage of this vaccine was also higher in this group (22%, 95% CI 16–29). In the majority of patients (influenza vaccine, 98% and pneumococcal vaccine, 94%), vaccination was carried out in general practice. Only 2% of patients had received pneumococcal vaccination in a hospital setting. The level of influenza and pneumococcal vaccination varied with the level of deprivation. Most GPs considered that the responsibility for influenza and pneumococcal vaccination lay with them. Forty-five percent of GPs reported having a written policy with set target for influenza vaccination and 11% for pneumococcal vaccination.

Following the Nipah virus (NV) outbreak in March 1999 in Singapore, a serological survey was undertaken to screen individuals potentially exposed to NV. Blood samples were tested for NV IgM, IgG and neutralizing antibodies. Twenty-two (1·5%) of 1469 people tested had antibodies suggesting NV infection. Although 12 of the 22 infected people (54·6%) were symptomatic, the remaining 10 (45·4%) were clinically well and had no past history of compatible pulmonary or neurological disease. Clinical and serological findings suggested three people had been infected with NV before the outbreak was recognized. All those who were infected were male abattoir workers. None of the people who had contact with horses, and no healthcare workers exposed to infected patients and their specimens had detectable antibodies. This study provides evidence that NV causes asymptomatic infection. All of the antibody positive individuals had direct contact with pigs and there was no evidence of human to human transmission.

Sera from an age-stratified sample of 4188 individuals, submitted for diagnostic purposes to 15 public health laboratories in England and Wales in 1996, were tested for hepatitis A antibody. The serological profiles were consistent with declining incidence in the past. This hypothesis was tested by comparing the serological profiles of Ashford, Leeds and Preston public health laboratories with those from sera collected during a previous study in the same laboratories in 1986/7. A comparison of equivalent 10 year birth cohorts revealed that significant hepatitis A seroconversion had only continued in Ashford. However, it is probable that most seroconversions are due to vaccination and immigration rather than continuing viral transmission. Further population-based surveys collecting more in-depth social and demographic data are needed to confirm the main factors influencing hepatitis A seroprevalence and to explain the regional differences.

In order to investigate the serological relationship of Dobrava hantavirus (DOBV, originating from Slovenia) and the Dobrava-like Saaremaa virus (SAAV, recently discovered in Estonia) we analysed 37 human serum samples, 24 from Estonia and 13 from the Balkans, by focus reduction neutralization test (FRNT). Most of the Estonian sera (19), including all sera from Saaremaa island (12), reacted with higher FRNT end-point titres to the local SAAV; the majority of them (15 and 11, respectively), with at least fourfold or higher titres to SAAV than to DOBV. In contrast, out of the 13 sera collected in Slovenia, Bosnia-Herzegovina and Greece, only one reacted more strongly with SAAV (with a twofold higher titre), while 10 of these sera reacted more strongly with the local DOBV (9/10 with fourfold or higher titres). These results indicate that DOBV and SAAV define unique hantavirus serotypes.

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.