In discussions of the origin of new infectious diseases, prominence is usually given to dramatic infections acquired from animals (Lassa fever, Marburg and Ebola viruses) or from the environment (legionellosis). But these infections do not spread from human to human, and their impact on mankind can never be catastrophic. If a new infectious agent is to pose a major threat to the human species, it will need to kill tens or hundreds of millions of people over a short period of time (a few years), before vaccines and antimicrobial agents can be developed or effective blocks to transmission established. The 1918 influenza pandemic (total deaths about 20 million) almost came into this world-shaking category, but many of the deaths were presumably due to secondary bacterial pneumonia and this was the pre-antibiotic era. A similar airborne pandemic occurring today could spread globally within weeks by air transport and would have a greater impact. Smallpox arose long before the world became one from an infectious disease point of view, and although it caused devastating epidemics it did not have the opportunity to develop into the ‘major threat’ category. A significant proportion of people recovered, less virulent strains of virus (variola minor) appeared, and an effective vaccine not only kept it under control in many continents but finally eliminated it from the world. The plague (Yersinia pestis) influenced the course of history in Asia and Europe [1] but oven in its respiratory form could not in those days be transferred rapidly from continent to continent.

The efficacy of three proprietary glutaraldehyde disinfectants and their component bases was assessed using the duck hepatitis B virus (DHBV) model. Inactivation of infectivity of undiluted serum containing 106·8 ID50/ml DHBV was assessed after a mixture with an equal volume of disinfectant had stood at room temperature for 10 min. A dried spill of infectious serum was simulated using sterile filter paper disks, saturated with serum containing DHBV, dried and then exposed to test disinfectant for 10 min. Residual infectivity, and hence the reduction in virus titre, was determined by inoculation of dilutions of the treated samples into 1-day-old ducklings. A greater than 3 log10 reduction in virus titre could be demonstrated for the disinfectants as well as for some of their component bases. Disinfectant activity varied according to the method of viral presentation but a reduction of exposure time from 10 to 2·5 min did not diminish activity. The experimental protocol permits a comparative and quantitative assessment of the efficacy of both established and new disinfectants.

In a household survey in the Faroe Islands, an isolated community with hyperendemic occurrence of meningococcal disease due to serogroup B 15, 1604 persons were examined for pharyngeal carriage of Neisseria meningitidis and N. lactamica. Two areas were chosen having experienced high (HIA), and two having experienced low incidences (LIA) of disease. Living in HIA compared with LIA was associated with higher risk of N. meningitidis B 15 carriage and lower risk of N. lactamica carriage, with odds ratios of 2·7 (95% confidence interval (CI) 1·4–5·1, P = 0·003) and 0·41 (95% CI 0·31–0·53, P < 0·0001), respectively. In HIA the risk of N. meningitidis carriage was much lower in non-carriers than carriers of N. lactamica, with an odds ratio of 0·19 (95% CI 0·08–0·47, P = 0·0003); in LIA this association (odds ratio 0·51, P = 0·05) was much weaker. Children 0–14 years had substantially higher risk of being carriers of N. meningitidis group B 15 if the mothers were so, with an odds ratio of 11 (95% CI 4–29, P < 0·0001).

Isolates of Streptococcus pyogenes from vaginal swabs of children with vulvovaginitis received at Nottingham Public Health Laboratory during 1986–9 were studied. A total of 159 isolates was made during the 4 years, increasing from 17 in 1986 to 64 in 1989 and accounting for 11% of all vaginal swabs received from children. The numbers of throat swabs yielding S. pyogenes also showed an increase from 974 in 1986 to 1519 in 1989. A winter peak of isolates was noted for both vaginal swabs and throat swabs. A total of 98 strains from vaginal swabs were serotyped: 22 different types were identified, 61% of which were the common types M4, M6, R28 and M12. Erythromycin sensitivity was done on 89 strains; 84% were highly sensitive (MIC < 0·03 mg/1). There are no other reports of such large numbers in the literature; the reason for seeing this increase in Nottingham is unclear.

Biotyping, slime production, antibiograms, extrachromosomal DNA banding and total DNA restriction analysis were used to characterize Staphylococcus epidermidis strains causing cerebrospinal fluid shunt infections in 11 patients. Infections considered to be community acquired and those acquired in the first 2 weeks of hospital admission were due to oxacillin-susceptible isolates. Multiply resistant strains were isolated from patients who were in hospital for more than 1 month before tube implantation. Slime was detected in staphylococci for 54% of cases, but its expression varied. Strains from different patients could be differentiated from one another by the extrachromosomal DNA bandings and total DNA restriction patterns, but isolates from the same patient were usually similar. During the period of external drainage, epidemiological markers were useful in differentiating persistence of infection from contamination or re-infection by a new strain.

Enterotoxigenic Escherichia coli (ETEC) from Burma, central Africa (Rwanda and Zaire) and Peru, were screened by enzyme-linked immunoassays for the colonization factor antigens (CFAs) and putative colonization factors (PCFs): CFA/I, CFA/II, which consists of three coli surface-associated (CS) antigens, CS1, CS2 and CS3, CFA/III, CFA/IV (CS4, CS5, CS6), CS7, PCFO9, PCFO159.H4, PCFO166, and CS17. The highest proportion of ETEC with identifiable colonization factors (71%) were found in the strains from Burma, which were mainly positive for CFA/I (38%), but strains producing CFA/II (4%), CFA/IV (11%), CS7 (10%), CS17 (4%), PCFO159.H4 (2%) and PCFO166 (2%) were also found. Sixty-nine percent of the ETEC from central Africa were positive for known colonization factors. While CFA/I positive strains were important (12%), a higher number of ETEC producing CFA/IV (33%) and CS17 (24%) were found. Fifty-two percent of the Peruvian strains produced identifiable colonization factors. The largest group of strains produced antigens of the CFA/IV complex (17%), while ETEC producing CFA/II (6%), CFA/III and CS6 (2%), CS7 (6%), PCFO9 (6%), PCFO166 (8%) and CS17 (7%) were also found. These surveys show that there is a considerable variation in the proportions and types of colonization factor found in different geographical areas. From 29 to 48% of the ETEC did not possess an identifiable colonization factor. These were particularly of the LT only producing type. These results have important implications for vaccine formulation.

The purpose of this study was to examine whether certain salmonella serovars, other than Typhi and Paratyphi, may have an increased ability to enter the human body fluids. The data are based on over 20000 salmonella isolated from humans during 1984–9, among them 436 from extra-intestinal (EI) sources. The mean percentage of EI salmonella isolated in Israel (excluding Typhi and Paratyphi), was 2·1 %. In three serovars: S. 9, 12:1, v:-, Virchow and Saintpaul, the percentage of blood isolations and of EI isolations in general, was high. Among the frequent serovars, ser. Infantis and Hadar had a much lower percentage of EI isolations.

Over 5700 hens eggs from 15 flocks naturally infected with Salmonella enteritidis were examined individually for the presence of the organism in either egg contents or on shells. Thirty-two eggs (0·6%) were positive in the contents. In the majority, levels of contamination were low. Three eggs, however, were found to contain many thousands of cells. In eggs where it was possible to identify the site of contamination, the albumen was more frequently positive than the yolk. Storage at room temperature had no significant effect on the prevalence of salmonella-positive eggs but those held for more than 21 days were more likely (P < 0·01) to be heavily contaminated. In batches of eggs where both shells and contents were examined, 1·1% were positive on the former site and 0·9% in the latter.

Between November 1988 and January 1989, a total of 155 people in 36 reported outbreaks suffered gastrointestinal symptoms associated with eating Stilton cheese, produced from unpasteurized cow's milk in the English midlands. Symptoms were suggestive of a staphylococcal illness but extensive laboratory testing of cheeses implicated in several of the outbreaks failed to detect any pathogen, toxin or chemical. Control measures were implemented, and included a voluntary withdrawal of the implicated Stilton cheese from sale on 23 January 1989 and a subsequent decision to use pasteurized milk in production of the cheese.

Over a 2-year period, 25 families comprising of 181 individuals of all ages were longitudinally observed for the excretion of Campylobacter species. Faecal samples were taken from all persons with diarrhoea. Specimens were also taken from apparently healthy individuals and from domestic animals living within the confines of the study families at monthly intervals.

The overall diarrhoea attack rate was 19 episodes per 100 person-years with peak incidence in the 1- to 4-year-old age group (76/100 person-years). Eight (11·5%) of the total episodes were campylobacter-associated and the overall rate of campylobacter positive diarrhoeal episodes were 2·2 per 100 person-years. Of the 1002 stool samples from healthy individuals 32 (3·2/100 samples) were positive for campylobacter. The organism was most frequently isolated from children under 1 year of age both during diarrhoeal episodes (11·5 per 100 person-years) and non-diarrhoeal (11·1 per 100 samples). Multiple infections in a family were rare. In 19·4% of the occasions one or more animals were campylobacter positive. However, only in 7·7% of these occasions was a human infection recorded within 1 month after the animal was found to be positive.

The study showed that the epidemiology of campylobacteriosis in this community was distinct compared to that observed in developed countries.

In order to elucidate the effect of ceftriaxone therapy on the morphology of gut microflora, 11 human volunteers were treated with ceftriaxone, 1 g daily, given intramuscularly in one dose. Treatment continued for 5 days. Faecal microflora was analysed by digital image processing before, during and after the treatment period.

We derived simple numerical parameters which describe the morphologic composition of the flora. They were significantly influenced by the antibiotic, and returned to their baseline values more than 7 days after treatment was stopped. The procedure holds promise for clinical application.

We conducted a 4-year retrospective cohort study to better define the risk of haemolytic anaemia and haemolytic uraemic syndrome (HUS) in children following sporadic gastrointestinal infection with the O 157.H7 serotype of Escherichia coli. Of the 72 children infected with this organism, 9 (12·5%) developed haemolytic anaemia, 6 of whom had HUS. No child in a cohort of 72 age-matched controls with Campylobacter jejuni gastroenteritis developed haemolytic anaemia (P = 0·003). Females had a significantly greater risk of developing haemolytic anaemia after E. coli O 157.H7 infection than did males (8/29 females v. 1/43 males; P = 0·003). In a logistic regression model, female gender emerged as the only statistically significant risk factor for haemolytic anaemia (odds ratio 3·85; 95% confidence interval 1·24–12). These results are consistent with recent reports of a moderate increase in the risk of HUS for females.

Esterase electrophoretic typing and restriction fragment length polymorphism of ribosomal DNA regions (ribotyping) were used to differentiate 102 Pseudomonas aeruginosa clinical isolates obtained from chronic lung infection in 23 patients with cystic fibrosis (CF) and two reference strains (including the type strain ATCC 10145). Twenty-five zymotypes were obtained with the former method and 16 ribotypes with the latter. Combination of the two typing systems led to the finding of 30 different types. Our data highlights the physiopathological complexity of P. aeruginosa infection in CF as, in six individual cases, several types were found among isolates from a given patient. On the other hand, two unique types were found in two and three patients respectively, raising the possibility of crossinfections.

A slide agglutination (SA) test was developed to determine the serogroup of isolates of Treponema hyodysenteriae of serogroups A to F. Rabbit antisera which are normally used for serogrouping T. hyodysenteriae in an agarose gel doublediffusion precipitation test (AGDP) were not suitable for SA because they agglutinated isolates from more than one serogroup. The agglutination reaction was made serogroup-specific by cross-absorbing the typing sera for serogroups A to F with whole treponemes from the other 5 of these 6 serogroups of T. hyodysenteriae. The absorbed sera were reacted in slide agglutination tests with 33 isolates of T. hyodysenteriae and with four non-T. hyodysenteriae intestinal spirochaetes. None of the non-T. hyodysenteriae isolates agglutinated, but 27 of the 33 isolates of T. hyodysenteriae did. The results for 26 of the 27 agglutination reactions agreed with the serogroup as determined in AGDP. One of the 6 isolates of T. hyodysenteriae which failed to react in slide agglutination was of serogroup B, 1 of serogroup D, 1 each were from new serogroups G, H and I, and 1 was untypable in AGDP.

A survey for leprosy among 565 armadillos from Louisiana and Texas found IgM antibodies to the phenolic glycolipid-l antigen of Mycobacterium leprae in 16% of the animals. There were no geographic trends in the distribution of prevalence rates between the sites and the disease probably has a much greater range. Repeat observations in one location showed significant seasonal variations in the observable antibody prevalence rate, but the yearly average remained similar. Infected armadillos tended to be heavier, and the females usually had plasma progesterone concentrations indicative of sexual maturity. Using these characteristics to stratify the populations into adult and sub-adult cohorts, variations in the observable leprosy prevalence rate were seen to be proportional to changes in the age structure of the populations. Leprosy appears to be maintained in steady state within some regions, and nearly a third of the adult armadillos in Louisiana and Texas harbour M. leprae.

A total of 100 serum samples including 22 acute phase sera and 39 paired sera collected from clinically diagnosed cases of leptospirosis in Ming-shan County, Sichuan Province, China were examined by the one-point microcapsule agglutination test (MCAT), which was developed in Japan, and by conventional microscopic agglutination tests (MAT). The one-point MCAT is more reactive to IgM antibody than MAT and is superior in detecting antibodies in the early stages of the disease.

The incidence of Ockelbo disease and the prevalence of Ockelbo virus neutralizing antibodies were investigated in a sample of the Swedish population. The disease occurs throughout most of Sweden but with higher incidence and antibody prevalence rates in the central part of the country. It generally affects middle-aged men and women, with equal incidence between sexes, and is uncommon in people younger than 20 years of age. The disease occurs during a short period each year between the third week of July and the first week of October, with a peak during the second half of August. During the 8 years studied (1981–8), an average of 31 Ockelbo patients/year were diagnosed. The antibody prevalence rates in the oldest age groups were 20–40 times higher than the accumulated life-risk of being diagnosed and reported as an Ockelbo disease patient, which suggests that many cases are asymptomatic and/or unreported.