Characterization of the incubation time from infection to onset is important for understanding the natural history of infectious diseases. Attempts to estimate the incubation time distribution for novel A(H1N1v) have been, up to now, based on limited data or peculiar samples. We characterized this distribution for a generic group of symptomatic cases using laboratory-confirmed swine influenza case-information. Estimates of the incubation distribution for the pandemic influenza were derived through parametric time-to-event analyses of data on onset of symptoms and exposure dates, accounting for interval censoring. We estimated a mean of about 1·6–1·7 days with a standard deviation of 2 days for the incubation time distribution in those who became symptomatic after infection with the A(H1N1v) virus strain. Separate analyses for the <15 years and ⩾15 years age groups showed a significant (P<0·02) difference with a longer mean incubation time in the older age group.

Risk factors for cervical infection with human papillomavirus (HPV) were assessed among 236 Italian women at risk for human immunodeficiency virus (HIV) infection (intravenous drug users (IVDU) or sexual partners of males at risk for HIV infection). All study participants underwent a structured interview, determination of HIV serostatus and detection of HPV cervical infection by means of polymerase chain reaction (PCR). Overall, the cervical presence of HPV DNA was ascertained in 86 of these 236 women (36·4%), while squamous intraepithelial lesions (SIL) were diagnosed in 57 (24·1%). HPV-infected and non-infected women did not differ in age, education and cigarette smoking. A statistically significant trend in the risk of HPV infection with increasing number of lifetime sexual partners was noted (P=0·01), but such trend was attenuated in multivariate analysis (multiple logistic regression (MLR) odds ratio (OR) for [ges ]20 partners vs 1=1·6, 95% confidence intervals (CI): 0·4–5·9). A nearly threefold higher risk of HPV cervical infection emerged among IVDU women (MLR–OR: 2·7, 95% CI: 1·4–5·0), and this difference was not influenced by HIV serostatus. The prevalence of HIV infection was higher among HPV-positive than HPV-negative women (62·8% and 54·0%, respectively) (MLR–OR=1·9, 95% CI: 0·9–3·8), and the proportion of women with less than 200 CD4+ cells/mm3 was slightly and not significantly higher among HPV-positive (47·1%) than negative women (37·2%).

Typhus Fever is a disease which modern sanitary reform has banished from the midst of progressive communities. As a result few opportunities are now afforded for investigating the disease by the bacteriological methods of to-day. Sporadic cases and small epidemics occur from time to time in the few insanitary districts that remain in Belfast. Dr Ernest H. Milligan and I made some observations of a bacteriological nature on this disease which we communicated to the Ulster Medical Society in 1908. Since that time I have continued the investigations when any opportunity occurred and in this paper are recorded the results which have been obtained. Recently some new light has been thrown on the etiology of typhus fever, so the present time appeared to me to be opportune to publish our own observations, to analyse the findings of other observers and to discover what is truly established with regard to this subject.

A prospective survey was conducted in patients admitted to 11 randomly selected general practices and eight hospitals located in six provinces of Poland. For each patient meeting the international acute gastrointestinal infection (AGI) case definition criteria, information was collected on healthcare resources used. Antibacterial drug consumption was assessed using defined daily doses (DDD) and extrapolated to the national level using results from a parallel study of AGI incidence in the community. Additionally, a logistic multivariable model was fitted assessing determinants of antibacterial drug administration. Valid questionnaires were collected from 385 general practitioner (GP) consultations and 504 hospital admissions. Antibacterials for systemic use were prescribed during 60 (16%) GP consultations and 179 (36%) hospital admissions. The estimated societal AGI-related consumption of antibacterials amounted to 5·48 million DDD (95% uncertainty interval 1·56–14·12 million DDD). Antibacterial prescription was associated with work in large practices [adjusted odds ratio (aOR) 3·16] and hospital wards (aOR 2·87), compared to small general practices, referral for microbiological testing (aOR 2·88), presence of fever (aOR 2·50), presence of mucus or blood in stool (aOR 1·94), age >65 years vs. <5 years (aOR 1·88), and rural vs. urban residence (aOR 1·53). Despite the fact that antibacterials were prescribed to a minority of consulted AGI patients, their consumption in society was not negligible due to the high prevalence of AGI symptoms. Prescription of antibacterial drugs should be restricted to cases with specific indications, preferably following microbiological investigation of AGI aetiology. To achieve this, clear national recommendations should be widely disseminated to physicians, and included in medical training curricula.

Because of recent reports of abortion in farmers' wives following infection with ovine strains of Chlamydia psittaci during pregnancy, the distribution of chlamydial antibodies was studied in rural populations in north-west England, where endemic chalamydial infection with abortion in common in sheep. Immunoperoxidase assays with C. treachomatis and ovine C. psittaci showed no significant differences in either the frequency or titres of antibodies between sheep farmers and other types of farmer or non-farming adults living in the same areas. The frequency and titers of antibodies in farmers' wives were no greater than in farmers, and were unrelated to their previous obstetric history or type of farming. Overall, 62/255 (24%) of this rural population had antibody detected by C. trachomatis antigen and only 30/255 (13%) detected by C.Psittaci antigen. The possible significance of these findings is discussed. This survey does not suggest that the risk of infection with C.psittaci is especially high in people working with sheep, but the complications following infection during pregnancy deserve the specific instructions that have been given to pregnant women to avoid exposure, especially during lambing, in farming and veterinary work.

The literature on the dissemination of helminth ova by flies is reviewed. In experiments using various species of filth flies, it was shown that ova of Taenia saginata Goeze 1782 can be passed out for periods of up to 11 days after ingestion, and viability of such ova was demonstrated for three days after ingestion. The possible methods of dissemination of ova are discussed together with the longevity of ova on pasture and the dispersal habits of flies. It is suggested that in Kenya, filth flies may play an important role in the epizootiology of bovine cysticercosis.

In one locality in Italy where the incidence of psittacosis has increased rapidly since 1980, a hospital-based study and a seroepidemiological survey were carried out in order to define the clinical and epidemiological features of psittacosis in that area.

Registers of the Virology Unit of the University of Ancona, Italy, were reviewed and all hospitalized patients with a serological diagnosis of psittacosis were identified. A total of 76 cases were found and studied. A presumptive bird source was identified in 80% of 62 patients, on whom a detailed investigation had been possible. Poultry represented the most frequent probable source of infection. Clinically, the predominant pattern of illness was a moderately severe lower respiratory tract infection, with chest X-rays showing pulmonary shadowings in 68 patients (89%).

In the seroepidemiological study, 51 out of 143 subjects were exposed to birds (35·7%), but only 7 out of 90 urban adult blood donors (7·3%) were positive for chlamydial antibodies using the microimmunofluorescence test.

A total of 522 Danish blood donors were followed during 2004–2005 to describe the seroepidemiology of Legionella infections in healthy individuals from a general population. Antibodies to Legionella spp. were measured by indirect immunofluorescence antibody test. The prevalence of Legionella antibodies (titre ⩾1:128) was 26·8% and remained fairly constant during the year of follow-up. However, 6·9% of the blood donors developed a fourfold or greater rise in antibody titres. A history of visits to Danish summer cottages was associated with both Legionella seropositivity (OR 1·53, 95% CI 1·02–2·30) and seroconversion (OR 2·66, 95% CI 1·21–5·83). There were no consistent associations between either levels of antibody titres or seroconversion and self-reported health symptoms, absence from work due to illness, or to any risk factors. We conclude that community-acquired Legionella infections are frequent; however, they rarely result in severe illness.

In an established burns centre which moved from an old building to new purpose-designed premises, colonization rates of patients' burns with Staphylococcus aureus, Pseudomonas aeruginosa and other Gram-negative bacilli were not reduced. Colonization rates with Streptococcus pyogenes increased but the increase was mainly due to multiple importations in the new premises of a strain of higher communicability than any seen in the old.

In the first 32 months in the new environment 10 patients were found colonized with pseudomonas on admission and 20 became colonized in the unit. A much higher proportion of patients with burns of more than 30% body surface became colonized than of patients with less. About one-third of the above 20 patients became colonized with strains already isolated from another patient; all but one of them had small area burns. Cross-infection was not observed from numerous heavily colonized patients with high percentage burns. This paradox is discussed in detail. Basin outflows in the new premises became colonized with P. aeruginosa of two serotypes not found on patients in this unit.

Argentina incorporated rotavirus massive vaccination in 2015. No specific strategy has been designed to accurately measure the impact of this recent introduction on the diarrhoeal disease burden in our country. We assessed post-vaccine introduction data (all-cause acute diarrhoea and rotavirus laboratory-confirmed cases, and genotype distribution), compared with pre-vaccination period in children under 5 years of age in Argentina. Cross-sectional ecologic analysis was conducted with data from the Argentine Surveillance Health System. Endemic channel and global and seasonal incidence rates of pre- and post-vaccination periods were calculated and further compared. Conventional binary genotypification on rotavirus-positive samples was also performed. In post-vaccination period, a global decrease of 20.8% in the rate of all-cause acute diarrhoea cases was found. The endemic channel showed that declination was more significant in the autumn/winter season. Rotavirus laboratory-confirmed cases showed 61.7% of reduction and the weekly distribution analyses indicated a significant flattening of the expected seasonal peak. G2P[4] was the most prevalent circulating genotype (57.2%). This study represents the first assessment of diarrhoeal disease burden since rotavirus massive vaccination strategy was implemented in Argentina. This introduction represented a successful intervention due to the significant decrease in all-cause acute diarrhoea cases and rotavirus laboratory-confirmed cases.

A retrospective study of 258 children admitted to Ruchill Hospital, Glasgow, with croup between 1966 and 1972 indicated that the viruses most frequently associated with the syndrome were parainfluenza types 1 and 3 and influenza A. Most cases were admitted in the late autumn and winter months, with a small peak in May and June. This seasonal distribution mirrored the circulation of the main causative agents in the community, parainfluenza 1 being principally associated with the autumn cases, influenza A the winter cases and parainfluenza 3 the summer cases. Two of these ‘croup associated’ viruses showed regular periodicity, parainfluenza 1 occurring biennially in even years and influenza A in most years. The periodicity of parainfluenza 3 is as yet undetermined.

Varicella, usually a mild disease of childhood, can also cause complications and hospitalization. Universal varicella immunization is implemented in several countries worldwide, but not in Denmark. Taking advantage of unique national registers, we aimed to estimate the incidence of paediatric varicella hospitalizations and assess determinants for hospitalization. For this purpose, we designed a nationwide, retrospective register study of paediatric varicella hospitalizations and applied a case–cohort design and logistic regression analysis comparing hospitalized varicella patients to a sample of the entire paediatric population in Denmark. Varicella patients were identified in The Danish National Patient Register and referents were randomly selected from the Danish Civil Registration System. The incidence of paediatric varicella admissions was 11/100 000 children 0–18 years of age/year. Of admitted children 67·1% had complications and 30·0% had underlying disease. All categories of underlying disease significantly increased the odds of hospitalization as well as male gender and not having been born in Denmark. In conclusion, we found a considerable burden of paediatric varicella disease in Danish hospitals, of similar magnitude as in other European countries comparable to Denmark. With this study we have provided epidemiological data needed for considering implementation of varicella vaccine in Denmark.

The two processes involved in the phagocytosis of bacilli (B. typhosus) by polymorphonuclear leucocytes in the presence of a sensitising fluid, viz. (1) the sensitisation of the micro-organism, and (2) the phagocytosis of the sensitised micro-organism, have been separately investigated. A single guinea-pig end-piece acted as the sensitising fluid throughout all the experiments.

The removal of opsonin by bacillary emulsions was found to run the course of an adsorption process as evidenced by the numerical relations found to subsist between the bound and free opsonin in equilibrium.

Also the actual phagocytosis of sensitised or partially sensitised micro-organisms suspended in a neutral fluid (physiological saline) was found, on analysis by similar numerical methods, to proceed as an adsorption process.

1. Strains of Bact. coli and related bacteria possess a life cycle resembling that of Myxobacteria. The vesicular, resting nucleus is contained in a microcyst, which is formed by a process suggestive of sexual conjugation.

2. The microcyst germinates by the transformation of the resting nucleus into the chromosome-like bodies typical of active, vegetative cultures. These may be analogous to the chromosome complexes of yeasts. The period of germination of microcysts corresponds to the lag phase of cultures.

3. The nucleus remains permanently in the mitotic condition during the active, vegetative phase of growth, and reproduces by an asexual and a sexual method.

4. Older cultures may be transformed directly into microcysts or may first adopt a secondary, vegetative phase, in which the nucleus is in the form of a single, central body.

5. Microcyst formation differs from spore formation in that it lacks the obvious reduction processes associated with spore formation, upon which a few original observations are included.

Better control of highly pathogenic avian influenza (HPAI) outbreaks requires deeper understanding of within-flock virus transmission dynamics. For such fatal diseases, daily mortality provides a proxy for disease incidence. We used the daily mortality data collected during the 2015 H5N2 HPAI outbreak in Minnesota turkey flocks to estimate the within-flock transmission rate parameter (β). The number of birds in Susceptible, Exposed, Infectious and Recovered compartments was inferred from the data and used in a generalised linear mixed model (GLMM) to estimate the parameters. Novel here was the correction of these data for normal mortality before use in the fitting process. We also used mortality threshold to determine HPAI-like mortality to improve the accuracy of estimates from the back-calculation approach. The estimated β was 3.2 (95% confidence interval (CI) 2.3–4.3) per day with a basic reproduction number of 12.8 (95% CI 9.2–17.2). Although flock-level estimates varied, the overall estimate was comparable to those from other studies. Sensitivity analyses demonstrated that the estimated β was highly sensitive to the bird-level latent period, emphasizing the need for its precise estimation. In all, for fatal poultry diseases, the back-calculation approach provides a computationally efficient means to obtain reasonable transmission parameter estimates from mortality data.

An unusually high incidence of Vibrio cholerae O1 infection was observed in southern Thailand between late December 1997 and March 1998. Fifty-seven V. cholerae O1 strains were isolated in five provinces during this epidemic and were examined. They were El Tor Ogawa strains exhibiting similar antibiograms. All strains were resistant to tetracycline, which had not been reported in Thailand since 1993. The ribotypes, hybridization patterns with ctx and zot gene probes, arbitrarily primed PCR profiles, and pulsed-field gel electrophoresis profiles of the representative strains were compared with the clinical strains isolated from patients in India and Bangladesh in 1997 and 1998 and from international travellers originating from various Asian countries during the 1992–8 period. All southern Thailand strains and the 1998 international traveller strain of Thai origin showed indistinguishable genetic fingerprinting patterns that were distinct from those of other test strains. The results suggest that a tetracycline-resistant clone newly emerged in late December 1997 caused the large epidemic in southern Thailand and that the variants with a slightly different antibiogram appeared during the course of the spreading epidemic.

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.

The relationship between the serological findings for brucellosis and the epidemiological factors has been studied in veterinary surgeons in Northern Ireland. The anti-human globulin (Coombs) test and the complement-fixation test for brucella were used in two groups of veterinary surgeons, those self-employed and those employed by the Ministry of Agriculture.

Significant serological differences were found to exist between the two groups. Those in private practice showed changes related to age, cattle skin rash, reactions to S. 19 vaccine accidents and symptoms suggestive of brucellosis in the past or the last year. But those working for the Ministry only showed titre changes related to the length of their private practice experience before joining the Ministry. In neither group was there a relationship between serological findings and the type of milk drunk or any particular group of symptoms suggestive of brucellosis.

The findings indicate that high titres to brucella by the Coombs and complement-fixation test can occur in people repeatedly exposed to infection at work. Titres which would be of diagnostic importance in the rest of the population may be of little diagnostic significance even when they are as high as 160 Coombs and 128 complement fixation.

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae compromises patient treatment and disease control. Epidemiologically based surveillance of AMR in gonococci is needed to optimize standard treatment regimens. Validation of AMR surveillance data depends on external quality assurance schemes (EQAS). AMR surveillance data quality in India during 2001–2007 was assessed by participants testing panels of reference strains and repeated re-challenge with identical controls, accompanied by educative feedback. Overall, correct results were obtained for 944 (82%) of 1030 tests performed for five ‘core’ antibiotics. Aggregated error rates decreased from 33% (123 tests) in 2001 to 4·4% (180 tests) in 2007 with improvements in individual laboratory performance. Cephalosporin test results produced high error rates without improvement. Reference centre and network laboratory collaboration produced marked improvements in test performance through annual EQAS integrating proficiency testing and participant education. More frequent EQAS cycles would assist this process. These experiences may be applicable in similar settings elsewhere.

1. Standard Bact. coli cultures have been heated at 51° C. in phosphate buffered media having pH values ranging from 2·8 to 8·8, and survivor curves obtained.

2. Except at pH 3·9, the first continuous decline in viable numbers was followed by the establishment of a small fluctuating residual population which was apparently permanent.

3. The colony counts showed a moderate excess of unduly high values of x2, the bulk of which were encountered when the mortality was between 95 and 99·999%.

4. Prolonged incubation of the plates led to increased colony counts, but the rise was confined to the active disinfection phase. It occurred chiefly in the 95–99·999% mortality range and was moderate in degree. The x2 values were little affected.

5. The log survivors-time graphs of the disinfection phase were convex in type but approached linearity in the faster reactions. The logarithmic death-rate became maximal at about 90 % mortality and thereafter remained constant, though under the more acid conditions a somewhat lower rate was maintained. At pH 7·0 and 6·4 the curves were exceptionally straight.

6. Standardization of all the curves revealed a continuous change in shape with pH but, nevertheless, they could be placed in three closely knit overlapping groups which were best revealed by the variation in maximum death-rate.

7. The 50–99·99% mortality times were obtained either from the calculated regressions of log survivors on time over the linear portions of the curves or, outside that range, from the freehand curves. Maximum survival at all mortality levels occurred at about pH 6·5–6·6, i.e. close to the neutral point of pure water at 51° C. On both sides of this point sensitivity increased regularly but was abnormally high at pH 7·0 and 6·4.

8. Within these zones of abnormally high sensitivity the assessment of the effect of a given change in pH varied in amount and direction according to the mortality level chosen.

9. The enhanced resistance of a culture regenerated from the survivors of a disinfection at 51° C. and pH 7.0, as previously reported, could possibly have been largely due to a small increase in acidity but not to a slight shift towards alkalinity.