Sera from people born between 1883 and 1930 and collected in 1977 were tested for the presence of HI antibodies to A/FM/1/47 (H1N1) virus and three recently (1977 and 1978) isolated influenza A-H1N1 viruses. The highest frequency of high-titred antibody to the four H1N1 viruses was detected in sera from people born in 1903–4, i.e. 42,54,38, and 22% had antibody against A/FM/1/47, A/Hong Kong/117/77, A/Brazil/11/78, and A/Fukushima/103/78 respectively. The birthdate groups 1896–1907 showed a higher percentage of HI antibody titres ≥18, ≥50, ≥100 or ≥1600 against the four H1N1 viruses than the birthdate groups 1907–30. This indicates the existence of an era, 1908–18, in which, apart from the H3N2 virus (1900–18), the H1N1 virus was epidemic among the human population.

Trimethoprim resistance was plasmid-encoded in all trimethoprim-resistant Salmonella typhimurium and in the majority of trimethoprim-resistant salmonellas of other serotypes isolated since 1970 from humans and food animals in Britain. In S. typhimurium, non-autotransferring plasmids of compatibility group 3 and autotransferring plasmids of group H2 predominated. The predominance of these plasmid types has resulted from the spread of clones of trimethoprim-resistant strains of phage types 18,170 and 204c. In other salmonellas, a variety of plasmid compatibility groups have been identified. Almost all plasmids which conferred resistance to trimethoprim also coded for sulphonamide resistance.

A five-tube most probable number (MPN) method, with pre-enrichment and enrichment stages, was used in a study of the incidence of salmonella contamination of British fresh sausages and the ingredients used in their manufacture. All samples were taken from a large factory in the course of routine production. There was an incidence of 65 % contamination of pork (n = 20) and 55% (n = 20) in pork and beef sausages. The incidences of contamination of uncooked ingredients varied from 95 % for mechanically recovered meat (n = 20) to 10 % for another type of meat. Cooked and/or dried ingredients were rarely contaminated with these organisms and, when contamination occurred, coliforms were also important.

The numbers of salmonellas isolated ranged from 7–40 for pork sausages, from 8–24 for beef and pork sausages and from 0·8–378 organisms/g for ingredients.

The following salmonella serotypes were isolated (ranked in descending order of incidence): S. derby, S. dublin, S. newport, S. stanley, S. typhimurium, S. heidelberg, S. infantis and S. agona.

A total of 1799 swine sera collected in Toyama prefecture in the central part of Japan during the years 1978–82 were tested for antibody against swine influenza virus (SIV), A/New Jersey/8/76 (H1N1). A high prevalence of antibody was observed in the years after the severe epizootic of SI, 34·5% in 1979 and 51·7% in 1982. In other years, the percentages of positive sera were low and ranged from 1·7 to 12·4%. Regional variations were seen in relation to a small scale epizootic. No antibody to SIV was detected in any of the sera collected during the warm season. In the following dry and cold winter, however, a severe epizootic occurred among the swine populations.

Outbreaks of abortion associated with infection by Salmonella montevideo have affected sheep in the east, especially the south-east, of Scotland each year since 1972. Disease in the north and north-east was usually less severe.

Between 1 January 1970 and 31 December 1981, a total of 67 incidents affecting sheep were reported by veterinary laboratories to the Communicable Diseases (Scotland) Unit, 87 % of which presented during the main lambing months of February, March and April. Twenty-one episodes of bovine infection were also recorded over the same period, 17 of which involved single animals only, usually an aborted cow or a scouring calf.

Despite intensive investigations, neither the origin nor the mode of spread of S. montevideo infection among sheep and cattle in Scotland has been established with any certainty, although there has been considerable evidence indicating the role of scavenging wild birds, particularly seagulls, as vectors transmitting infection to other farms in the same district. Also largely unexplained are the differences in the epidemiology and clinical pattern of disease in the south-east compared to the north and north-east, while sheep in the west of Scotland have remained virtually unaffected throughout.

A seroepidemiological survey for toxocaral infection was performed using samples from children and adult women in the Yamaguchi area of Western Japan, An enzyme-linked immunosorbent assay using excretory–secretory antigen was applied to these sera. Of samples tested, 3·1% from children and 3·7% from women were positive. It was found that regression analysis of positive rates by age between 20 and 70 or more years was significant in the positive direction. The positive rates from urban, rural and fishing areas were 5·7, 3·9 and 1·7% respectively. Also, the rates from northern, western and eastern parts in the research area were 5·7, 4·7 and 0·5% respectively. These findings suggested that environmental factors are important for toxocaral infection. Further, the rate for 108 samples who answered that they have owned dogs was 6·2% compared to 2·9% of 422 respondents who denied an experience of owning dogs. This fact suggested thatattention should be paid to dog breeding for prevention and control of toxocaral infection in man.

Eight sera from 125 cases of infectious mononucleosis (IM) were reactive for rubella-specific IgM in an M-antibody capture radioimmunoassay. The reactivity of individual sera varied depending upon the source of the rubella antigen used in the assay. One serum gave strongly positive results with some rubella haemagglutinating antigens but negative results with others and may have contained an IgM antibody which was capable of distinguishing between strains of rubella virus.

If the diagnosis of rubella is based solely on detection in solid-phase immunoassay of rubella-specific IgM, IM should be excluded.

Twenty-nine strains of Corynebacterium diphtheriae isolated from throats and 29 strains from skin lesions, the latter mainly from communities of low socio-economic status in tropics and cold climates, have been examined for the property of adherence to human buccal epithelial cells. All throat strains showed adherence. In contrast, strains from skin lesions were predominantly poor adherers. These results indicate that strains of C. diptheriae from throats must now be added to the important group of pathogens which possess the property of adherence to surface epithelial cells of mucous membranes, thus providing an essential first step in the process of colonizing their hosts. The possible role of this phenomenon of adherence to bucco-pharyngeal epithelial cells in the evolution of the host—parasite relationship of C. diphtheriae is discussed.

The names Citrobacter koseri and C. diversus are synonyms for a species of enterobacterium with a particular ability to cause neonatal meningitis. 517 strains belonging to this species were examined using biotyping and serotyping techniques. 40 % of the strains belonged to serogroups O2 and O1 and 72 % belonged to biotypes d and a. Strains isolated from cerebrospinal fluid belonged to several different serogroups and biotypes but serogroups O2 and O3 and biotypes d and e were the most common. All the strains were resistant to ampicillin, 42 % were resistant to neomycin/kanamycin and 38 % were resistant to cephaloridine. 37 % of the strains were resistant to three or more drugs.

Sera were collected from female cattle in 118 commercial herds being subjected to a programme to eradicate brucellosis by test and slaughter, in an area in which vaccination of heifer calves with Brucella abortus strain 19 was compulsory. Of 4583 sera positive by the Rose Bengal plate test, the brucellosis radioimmunoassay was positive for 1524, the complement fixation test for 1363 and the indirect haemolysis test for 1141. These figures, and supporting evidence from the eradication programme, suggest that the radioimmunoassay may be a useful supplementary test in problem herds.

In a collaborative study 12 Public Health Laboratory Service laboratories and the Division of Hospital Infection, Central Public Health Laboratory, investigated the degree of contamination of standard dressings produced by manufacturers in India or in England by a comparison of the results of culture of 25 sterilized dressings with those of 25 untreated dressings. Of the 38 batches of dressings made in India 27 (71 %) were judged contaminated and another six could be so judged when Bacillus species were examined. In two batches laboratory contamination precluded a judgement and only three batches passed the test. Of the 27 batches made in England, only three gave any evidence of contamination at the lowest level of significance. Repeat investigation of one of these batches gave no evience of contamination.

Organisms of the genus Bacillus and fungi were associated with contamination; micrococci and propionibacteria were laboratory contaminants. There was evidence for both failure of sterilization and of contamination after sterilization during the manufacture of dressings.

A collection of more than 300 strains belonging to either Lancefield group C or group G was made. The cultures had been isolated either sporadically from patients with serious disease or as apparent clusters from various nosocomial outbreaks. T-protein antigens were sought. So far, nine distinct serotypes have been found among the group G streptococci and seven serotypes amongst the Streptococcus equisimilis (group C) strains. Of the sixteen serotypes, four were the original T-types 7, 16, 20 and 21 described by Griffith (1934). Because of the similarities of representatives of the two groups to Lancefield group A streptococci (Griffith, 1934; Maxted & Potter, 1967) a few strains not unexpectedly carried T antigens usually seen in group A streptococci. Using this scheme it has been possible to serotype 76% of S. equisimilis strains of human origin and 82% of group G streptococci from human clinical material. A small collection of group C and group G streptococci of animal origin could not be serotyped with the experimental T-antisera.

The properties of 48 cultures identified as Yersiniaenterocolitica or Y. enterocolitica like organisms, including Y. frederiksenii, Y. intermedia and Y. kristensenii, were examined. Of these, 39 were isolated from flieces of apparently healthy pigs, five from healthy cattle, one from an aborted bovine fetus, one from an aborted lamb and one from a lamb suffering from acute enteritis.

Most isolates from healthy animals were of Y. enterocolitica biotype 1 or Y. intermedia and belonged to O serogroups not usually associated with disease in man or animals.The isolates from abortion or enteritis cases were of Y. enterocolitica biotypes 3, 4 and 5 and belonged to the pathogenic serogroups 0:5b and 0:2a, 2b, 3. No organisms of serogroup 0:9 were found.

Infection of guinea-pigs by intranasal (i.n.) instillation of 109 viable organisms of two newly isolated strains of Legionella pneumophila (74/81, serogroup 1; 166/81, serogroup 3) did not induce disease, but 104 organisms administered as a small particle aerosol (< 5 μm diameter) produced a fatal widespread bronchopneumonia within 3 days. Milder illness and less extensive bronchopneumonia were also produced in rhesus monkeys and marmosets by one of these two strains (74/81). Mice were resistant to induction of disease by aerosols of both these two strains, though organisms did persist in the lungs for at least 4 days. Both of these L. pneumophila strains were pathogenic for guinea-pigs by aerosol infection over a wide range of doses but the serogroup 1 type strain (NCTC 11192) was not. There was no mortality after infection of guinea-pigs by intranasal instillation of any of these strains but all proved to be fatal after intraperitoneal (i.p.) injection of large doses. Guinea-pigs, rhesus monkeys and marmosets exposed to aerosol infection with L. pneumophila provide relevant models for studying the pathogenesis of Legionnaires' disease.

Faeces samples enriched for salmonellas in selenite F broth incubated at 43°C were subcultured to brilliant green MacConkey agar after 6 h. Four platings were made. As a control technique, each sample was enriched in selenite F incubated at 37°C for 24 h and subcultured once to brilliant green MacConkey agar. Of the specimens plated at 6 h, out of a total of 25 positive samples, 6 required more than a single subculture to reveal the presence of salmonellas. Twenty-four positive isolations were made from the selenite broths incubated at 37°C for 24 h and subcultured once only. All faecal samples positive by enrichment were also positive by direct plating. Nine samples seeded by 6 h produced only 1–2 salmonella colonies per plate. Convalescent specimens are, therefore, unlikely to be efficiently diagnosed by early subculture even if it is combined with multiple plating.

River Taff samples, after pre-enrichment in buffered peptone water, were enriched in Rappaport's medium at 37°C for 6 h. Subcultures were made to four plates of brilliant green MacConkey agar. A control subculture was made at 24 h to a single plate of brilliant green MacConkey. Although multiple subculture at 6 h improved salmonella isolation, the method was not as efficient as a single plating from the same enrichment culture at 24 h. There was no evidence that subculture at 6 h combined with multiple plating had a value either for faecal examination or for the isolation of salmonellas from sewage-polluted natural water.

Samples of other natural waters submitted routinely by Environmental Health Officers were pre-enriched in buffered peptone water before subculture to Rappa port's medium. The enrichment cultures were incubated at 37°C for 24 h and duplicate platings were made to brilliant green MacConkey agar. By double plating at 24 h, a gain of 16% in salmonella recovery was made. This compares favourably with the gain obtained by subculture from Rappaport after 24 and 48 h incubation. It also saves 24 h in examination time.

Concentrations of the rodenticide ergocalciferol (vitamin D2) in samples of rodent baits laid in foodstores and in the laboratory were monitored over several months. Bait samples were solvent extracted and ergocalciferol concentration determined by high pressure liquid chromatography (HPLC). Ergocalciferol levels were constant for more than 21 days in dry samples and did not fall by more than 30% in 100 days. When water (10% w/w) was added to the baits in the laboratory the ergocalciferol concentration fell by approximately 30 % in 30 days. In these wet laboratory samples there was a rapid visible growth of fungus and in normal rodent control use baits should have been replaced when such deterioration became evident.

This paper uses relatively simple and deterministic mathematical models to examine the impact that different immunization policies have on the age-specific incidence of rubella and measles. Following earlier work by Knox (1980) and others, we show that immunization programmes can, under some circumstances, increase the total number of cases among older age groups; the implications for the overall incidence of measles encephalitis and of congenital rubella syndrome are examined, paying attention both to the eventual equilibrium and to the short-term effect in the first few decades after immunization is initiated. Throughout, we use data (from the U.K., and U.S.A. and other countries) both in the estimation of the epidemiological parameters in our models, and in comparison between theoretical predictions and observed facts. The conclusions defy brief summary and are set out at the end of the paper.

Much evidence of immunogenic heterogeneity among the LC strains of Mycoplasma mycoides ssp. mycoides emerged from cross-immunization and hyperimmunization experiments in mice in which three LC strains (Vom/Plum Island, 74/2488, and Mankefår 2833) were used for challenge purposes. All heterologous LC-strain vaccines cross-immunized against the three challenge strains, but protection was usually only ‘partial’, i.e. significantly less than that given by homologous vaccine. Cross-hyperimmunization with all heterologous LC but not SC strains produced protection against challenge with Vom/Plum Island that was virtually ‘complete’, i.e. similar to that produced by homologous vaccine. Challenge with 74/2488 gave generally similar results; but against Mankefår 2833 six heterologous LC vaccines gave complete protection and six did not.

Vaccines prepared from the Smith (1423) strain of M. mycoides ssp. capri gave some protection against Vom/Plum Island but none against 74/2488 or Mankefrr 2833. The cross-immunizing ability of three further M. mycoides ssp. capri strains appeared to resemble that of Smith (1423).

In a cross-hyperimmunization experiment, vaccines prepared from SC strains of M. mycoides ssp. mycoides varied greatly in their ability to protect against challenge with strains 74/2488 and Mankefår 2833.

The pattern of phage types of 2553 strains of Salmonella typhi isolated over the 10-year period 1970–9 was studied. During the period 29 different phage types were encountered, not including the categories of ‘untypable strains’, ‘degraded Vi-strains’ and Vi negative strains. For the period as a whole, the commonest phage types encountered were A (20·9%), E1 (14·8%), D1 (10·3%), degraded Vi positive strains (10·3%), untypable Vi strains (7·3%), C4 (7·1%), D2 (4·4%), E2 (3·9%) and type 25 (2·6%). There were phage types which appeared in the early years of the period and then disappeared (types B2, D9 and D1-N). Others only made their appearance in recent years (K1 and 53). Notable differences were also seen in the predilection of some phage types for certain geographical areas.

Aqueous suspensions of virulent Legionellapneumophila grown on solid medium retained virulence and aerosol survival characteristics for several months. Significant numbers of viable organisms were recovered from aerosols held at various relative humidities (r.h.) for up to 2 h. The organisms survived best at 65% r.h. and were least stable at 55% r.h.

Exponential phase broth-grown organisms survived poorly in aerosols in comparison with stationary phase broth cultures or organisms grown on solid medium, suggesting that the metabolic status of Legionella pneumophila organisms may be an important factor affecting their ability to survive in aerosols and cause respiratory disease.