The study was based on a computerized card index of 9161 patients who had at least one positive blood specimen in the Mycoplasma pneumoniae complement fixation test. A total of 12562 specimens from these patients had been sent to Statens Seruminstitut from hospitals and general practitioners during a 10·5-year period. The period encompassed a previously described endemic period in a 30-year study of the epidemiological pattern of M. pneumoniae infection in Denmark [1], The serological data presented support the hypothesis advanced here that a more than sixfold increase of children in day care might have contributed to a change in the epidemiological pattern. The correlation between age and level of specific antibodies, as well as persistence of seropositivity, were also investigated.

A seroprevalence study was carried out on 1757 outpatients consecutively seen in a sexually transmitted disease (STD) clinic in order to evaluate the sexual transmission of hepatitis C virus (HCV). A total of 1442 consenting patients were tested for hepatitis C, hepatitis B and human immunodeficiency virus type 1 (HCV. HBV, HIV - 1) antibodies. The relations between anti-HCV, anti-HBc and anti-HIV - 1 were studied. Of 73 anti-HCV positive reactions, 45 (61.6%) were confirmed by the recombinant immunoblot assay (RIBA). The proportion of individuals with anti-HCV was higher in outpatients with a history of sexually transmitted disease than without. It was 2.8% in non drug user heterosexuals and 2.9% in non drug user homosexuals. Intravenous drug users (IDU) had higher anti-HCV prevalence when a history of STD was taken into account (42.3% in subjects with STD versus 36.7% in subjects without STD). Among non drug user heterosexuals an association was found between anti-HCV and anti-HBc. These data suggest that sexual transmission of HCV occurs, although it seems to be less efficient than other parenteral modes of transmission. When a more sensitive and specific marker of HCV infection become available, a more accurate estimate of the frequency and efficiency of the sexual transmission will be possible.

A mathematical model for the epidemiology of rinderpest was developed, starting from a simplified descriptive analysis of the disease. A formula for the calculation of the probability of infection of a susceptible animal was first established. A deterministic failure threshold of the infection was then deduced. Deterministic and stochastic approaches were adopted using iterative methods on a computer. These allowed a description of the spread and the variability of an infection process in a population to be made. An illustration of the use of this model showed that, in some cases, variability effects due to stochastic factors were very important. In these particular conditions, the use of the deterministic model alone was not adequate for a good description of the infection. Consequently, improvements of the model were proposed in order to make it more realistic and to allow its use for the evaluation of the efficiency of field operations.

Rates of acquisition and loss of Brugia malayi microfilaraemia were estimated using the parasitological data of a cohort of population in Shertallai, South India. The rate of acquisition of microfilaraemia was found to be dependent on age but not gender. The decline in the rate of acquisition of microfilaraemia in adults above 35 years could be due to the development of acquired immunity. The mean reproductive lifespan for the periodic Brugia malayi adult female worm was estimated to be 34 years and it was independent of host age and gender. The age-specific estimated proportion of population at risk (microfilaria carriers who lost their microfilaria in course of time) of developing lymphoedema approximately mirrored the observed age specific prevalence of lymphoedema in the study-population. On an average, 99% of population at risk developed manifestations of disease. The estimated population at risk of developing disease in different endemic areas is compared and its epidemiological significance is discussed.

Commercially available kits for detection of hepatitis B surface antigen (HBsAg) and hepatitis B surface antibody (anti-HBs) by enzyme immunoassay (EIA) were evaluated in American Samoa during a public health programme to eliminate the transmission of hepatitis B. The first 19184 serum specimens obtained, representing 68% of the total cooperating population, were initially tested for anti-HBs, and those without detectable antibody were tested for HBsAg. All the antigen-positive serum samples, and a selection of the antigen-and antibody-negative specimens were tested by radioimmunoassay (RIA) for detection of both markers. Compared with the standard tests, the EIA kits for anti-HBs and HBsAg performed well; sensitivity and specificity were 90·3 and 96·0%, respectively, for antibody, and 97·8 and 97·9% respectively for antigen. Substantial disagreement between the EIA and RIA tests for HBsAg was found only for specimens considered weakly reactive by EIA. Few differences were found between three EIA method options for follow-up HBsAg testing of weakly reactive serum specimens; each option contributed about equally to improved test specificity for these ‘borderline’ specimens. Based on their demonstrated equivalence to the standard RIA tests, we conclude that the EIA kits for anti-HBs and HBsAg detection are suitable for use in hepatitis B control programmes in open populations.

A nation-wide survey was conducted to estimate the prevalence of Salmonella enteritidis and other salmonellas among Canadian commercial broiler flocks. Environmental (litter and/or water) samples from 226 of 294 (76·9%) randomly selected flocks were contaminated with salmonellas. Litter samples were more often contaminated with salmonellas than water samples (47·4 ν 12·3%). Fifty different salmonella serovars were isolated. The most prevalent serovars were S. hadar, S. infantis, and S. schwarzengrund; they were isolated from samples of 98/294 (33·3%), 26/294 (8·8%), and 21/294 (7·1%) flocks, respectively. Feed samples of 39/290 (13·4%) flocks were contaminated with salmonellas. Salmonella enteritidis was isolated from the environmental samples of 9/294 (3·1%) flocks. Salmonella enteritidis phage type (PT) 8 was isolated from seven flocks, and PT 13a from two flocks.

As part of the investigation of a putative bovine outbreak, 13 isolates of Salmonella typhimurium phage type 204c were subjected to plasmid analysis.Plasmid profiles suggested that several distinct strains were involved and these observations were supported by minor variations in antibiotic resistance pattern. Restriction enzyme fingerprinting and conjugational segregation of the plasmids confirmed these findings. Although 12 of the 13 isolates were resistant to gentamicin, resistance was conferred by 4 distinct plasmids; 3 of these belonged to Inc I and were distantly related on the basis of restriction fingerprints and the fourth was a resistant derivative of the 60 MDa S. typhimurium serotype-specific plasmid. The molecular evidence refuted the hypothesis that geographical and temporal clustering of these gentamicin-resistant isolates could be explained on the basis of a single epidmiological episode.

Neutralizing antibodies to sandfly fever Naples, sandfly fever Sicilian and Toscana viruses were investigated among 479 sera collected from a normal human population in Cyprus. Antibody prevalence rates of 57%, 32% and 20% were found to Naples, Sicilian and Toscana viruses, respectively. The observed frequency of dual and triple infections was higher than would be expected with a random chance of infection. Antibody prevalence rates were similar for men and women for all three viruses tested, but one of two study sites had significantly higher antibody prevalence to Naples and Sicilian viruses than the other. Individuals with antibodies to both Naples and Toscana viruses had higher antibody levels to Naples virus than those with antibodies to Naples virus only. If the antibody prevalence rates found in this study reflect a history of clinical disease as described in the literature, sandfly fever poses a significant public health problem in Cyprus.

Multilocus enzyme electrophoresis was used to examine genetic relationships among and between toxigenic and non-toxigenic isolates of Vibrio cholerae O1 obtained from patients and the environment in the US Gulf Coast and surrounding areas. A total of 23 toxigenic and 23 non-toxigenic strains were examined. All the toxigenic and 7 of the non-toxigenic strains had the same alleles at 16 enzyme loci, whereas the balance of the nontoxigenic strains had 9 distinct combinations of alleles. This study suggests that all of the toxigenic strains belong to a single clone, and that while some of the non-toxigenic isolates were related, most were of diverse origin.

We report a study to determine the presence of Listeria species in surface waters. One hundred ml volumes of 30 water samples taken from 21 different sites were analysed. Most of the samples examined were from ponds and lakes. Listeria species were isolated on eight (27%) occasions, six of these isolates were L. seeligeri, one was L. innocua and one L. welshimeri. Although not statistically significant, coliform and Escherichia coli counts were higher in waters that were positive than were negative for Listeria spp. It is suggested that the low isolation rate of listeria in this study reflects the fact that most waters examined did not receive sewage outfalls. Water sports activities are unlikely to be a risk factor for listeriosis.