Using data from a cohort study conducted by the Veterinary Laboratories Agency (VLA), evidence of spatial clustering at distances up to 30 km was found for S. Agama and S. Dublin (P values of 0·001) and borderline evidence was found for spatial clustering of S. Typhimurium (P=0·077). The evolution of infection status of study farms over time was modelled using a Markov Chain model with transition probabilities describing changes in status at each of four visits, allowing for the effect of sampling visit. The degree of geographical clustering of infection, having allowed for temporal effects, was assessed by comparing the residual deviance from a model including a measure of recent neighbourhood infection levels with one excluding this variable. The number of cases arising within a defined distance and time period of an index case was higher than expected. This provides evidence for spatial and spatio-temporal clustering, which suggests either a contagious process (e.g. through direct or indirect farm-to-farm transmission) or geographically localized environmental and/or farm factors which increase the risk of infection. The results emphasize the different epidemiology of the three Salmonella serovars investigated.

The inhibitory influence of cyanuric acid on the virucidal effect of chlorine was studied. The time required for 99·9% inactivation of ten enteroviruses and two adenoviruses by 0·5 mg/l free available chlorine at pH 7·0 and 25○C was prolonged approximately 4·8–28·8 times by the addition of 30 mg/l cyanuric acid. Comparative inactivation of poliovirus 1 by free available chlorine with or without cyanuric acid revealed the following. The inactivation rate by 1·5 mg/l free available chlorine with 30 mg/l cyanuric acid or by 0·5 mg/l free available chlorine with 1 mg/1 cyanuric acid was slower than by 0·5 mg/1 free available chlorine alone. Temperature and pH did not affect the inhibitory influence of cyanuric acid on the disinfectant action of chlorine. In the swimming-pool and tap water, cyanuric acid delayed the virucidal effect of chlorine as much as in the ‚clean’ condition of chlorine-buffered distilled water. The available chlorine value should be increased to 1·5 mg/l when cyanuric acid is used in swimming-pool water.

The properties of an atypical Brucella strain isolated from lymph node tissue of a cow slaughtered as a brucellosis reactor were examined. The organism was Gram negative and highly pleomorphic, existing as cocci, coccobacilli, rods, branched and irregular forms which stained with fluorescent antibody conjugates prepared against rough and smooth Brucella abortus strains. It produced lecithinase and required at least 15% v/v equine or bovine serum for growth. It did not need supplementary CO2 for growth, produced H2S and was inhibited by brucella dyes and partially by i-erythritol. Growth inhibition or lysis was produced by brucellaphages. The organism was not pathogenic for guinea-pigs or mice but evoked antibodies mainly to rough Brucella antigens.

1. Both in Bombay city and in the Amritsar district of the Punjab there is a distinct seasonal variation in the number of rat fleas.

2. In these places this seasonal variation of rat fleas corresponds directly in a general way with the plague mortality. During the season when plague is epidemic the average number of fleas per rat is above the mean, while during the non-epidemic season it is below the mean. The height of the epidemic corresponds fairly closely with the season of maximum flea prevalence.

The assemblages of Giardia duodenalis in 25 children with and 25 children without diarrhoea and 24 adults with gastrointestinal symptoms in South India were determined. Polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) targeting the glutamate dehydrogenase (gdh), β-giardin and triosephosphate isomerase (tpi) genes was used. The tpi PCR was the most sensitive and detected G. duodenalis in all 74 microscopy-positive samples, while gdh and β-giardin PCR were positive in 62·2% and 56·8% of the samples. Assemblage B was predominant in both children and adults (82·4%) followed by assemblage AII (9·4%); assemblage AI was not detected. Infections with both assemblages A and B (detected by tpi PCR–RFLP) were seen exclusively in children and the mixed assemblage BIII and BIV (detected by gdh PCR–RFLP) was more common in children than adults (P=0·058).

Truncated models are indirect methods to estimate the size of a hidden population which, in contrast to the capture–recapture method, can be used on a single information source. We estimated the coverage of a tuberculosis screening programme among illicit drug users and homeless persons with a mobile digital X-ray unit between 1 January 2003 and 31 December 2005 in Rotterdam, The Netherlands, using truncated models. The screening programme reached about two-third of the estimated target population at least once annually. The intended coverage (at least two chest X-rays per person per year) was about 23%. We conclude that simple truncated models can be used relatively easily on available single-source routine data to estimate the size of a population of illicit drug users and homeless persons. We assumed that the most likely overall bias in this study would be overestimation and therefore the coverage of the targeted mobile tuberculosis screening programme would be higher.

Photoinactivation of vaccinia virus sensitized by methylene blue had parameters similar to those observed with other viruses. Thus inactivation proceeded exponentially to completion, was irreversible, independent of temperature and the intensity of illumination. Inactivation was dependent on the dose of illumination and the concentrations of both methylene blue and hydrogen ions. The effects of pH appeared to be primarily concerned with the tenacity of dye-virus binding. Inactivation was inhibited by small amounts of nucleic acid but not by their bases or pentoses. Inactivation was only affected by the presence of extraneous protein in relatively high concentration: it was not affected by the enzymes catalase or peroxidase. Attempts to obtain direct chemical evidence of the participation of viral nucleic acid in photoinactivation were unsuccessful.

Recombination experiments strongly indicated the involvement of viral protein in photoinactivation. Immunogenicity was not impaired since good responses of neutralizing antibody were obtained in rabbits immunized with vaccines photoinactivated over a wide range of exposure times.

The screening and treatment of latent tuberculosis infection (LTBI) to prevent active tuberculosis (TB) is recommended by the WHO in all HIV-infected patients. The aim of this study was to evaluate its implementation within Belgium's HIV care. A multiple-choice questionnaire was sent to 55 physicians working in the country's AIDS reference centres. Response rate reached 62%. Only 20% screened all their HIV-infected patients for LTBI. Screening methods used and their interpretation vary from one physician to another. The main barriers to the implementation of LTBI screening and treatment, as perceived by the participants, are lack of sensitivity of screening tools, risks associated with polypharmacy and toxicity of treatment. The poor coverage of LTBI screening reported here and the inconsistency in methods used raises concern. However, this was not unexpected as, in low-TB incidence countries, who, when and how to screen for LTBI remains unclear and published guidelines show important disparities. Recently, a targeted approach in which only HIV-infected patients at highest risk of TB are screened has been suggested. Such a strategy would limit unnecessary exposure to LTBI treatment. This methodology was approved by 80% of the participants and could therefore achieve greater coverage. Its clinical validation is still pending.

A co-operative study was made of the incidence of infection acquired by patients in medical wards. Records were collected of 6740 admissions to 21 wards in 13 hospitals.

There were 384 clinical infections (5·7 per 100 patients admitted); 135 of them (35%) were infections of the lower respiratory tract, 72 (19%) were septic skin lesions or infected wounds, and 81 (21%) were urinary tract infections.

Infection was believed to have contributed to the death of 59 patients—17% of those infected or 8% of those dying in hospital. Nearly three-quarters of the deaths were attributed to ‘pneumonia’.

Acquired infections were most common and most severe at the extremes of age. There was an excess of males over females in staphylococcal infections and in infections of the lower respiratory tract, and of females over males in urinary tract infections.

The incidence of infection was above average in patients suffering from malignant disease, diabetes, rheumatoid arthritis, cerebral thrombosis and haemorrhage, and from diseases of the urinary tract and of the skin.

There were 110 acquired infections with Staph, aureus and 12 deaths were attributed to them. Over half of these infections were due to staphylococcal strains which caused only one clinical infection in a ward in the course of a year.

Pneumonia was difficult to diagnose in severely ill or moribund patients, and its clinical significance was hard to assess. It was not possible to obtain a reliable estimate of the part played by bacterial infection in its causation.

Certain strains of verotoxigenic Escherichia coli (VTEC), and in particular those belonging to serogroup O157, cause attaching and effacing (AE) lesions of the host gut mucosa during pathogenesis. The mechanisms involved with bacterial attachment and the destruction of microvilli are determined by a cluster of genes within the LEE region, which also encode five secreted proteins. Sera from patients with antibodies to the lipopolysaccharide (LPS) of E. coli O157 and other VTEC were tested for antibodies to these secreted proteins. Twenty-one of 34 (62%) sera with antibodies to the lipopolysaccharide (LPS) of E. coli O157 also contained antibodies to one or more of the secreted proteins. Five of 12 sera containing antibodies to the LPS of a range of other VTEC serogroups also contained antibodies to 1 or more of the 5 secreted proteins, as did 16 of 70 (23%) sera from patients with haemolytic uraemic syndrome (HUS), haemorrhagic colitis (HC) or diarrhoea, but without bacteriological evidence of infection with VTEC and which did not contain antibodies to VTEC serogroups O5, O115, O145, O153 or O157. The detection of serum antibodies to secreted proteins may provide additional information for interpreting the results of established lipopolysaccharide-based VTEC serology.

We know, since the time of Pasteur, that repeated passage of rabies street virus from rabbit to rabbit after intracerebral inoculation, leads to a modification of its effect and the appearance of mutative characters. This takes place at a variable period of time depending upon the strain employed. The irreversibility and the permanence of these characters has led to the name of “fixed virus” once the street virus has become adapted for the rabbit.

1. The influence of temperature on the germicidal power of selected disinfectants has been studied, and it has been found that germicides may be classified broadly into three main groups, viz.

Germicidal power (a) unaffected by rise in temperature: chiefly chemical substances, possessing reducing properties;

(b) approximately doubled by rise in temperature from 20 to 37°C.—phenol, alcohol;

(c) increased as much as 10 or 20-fold by the same temperature rise: oxidising agents.

2. The effect of temperature on bactericidal action is different for B. coli and B. fluorescens, thus causing very complex changes in selective action, which are discussed in this paper.

3. The temperature coefficient for the process of protein-precipitation by phenol is 2·2 per 10°C. rise in temperature, and thus similar in magnitude to the coefficient for disinfection by phenol. This supports the view that the germicidal action of phenol is associated with its denaturating effect on the cell-proteins.

4. Previous experimental work had suggested that the bactericidal action of the quinones was due to their chemical reactivity with the simple cell-constituents, e.g. the amino-acids, rather than with the complex colloids. The temperature coefficient of the reaction between benzoquinone and glycine is, however, the normal one, viz. 2 for 10° C. rise, for chemical action, although the germicidal action of the quinones may be actually 20 times more effective at 37° than at 20° C. The presence of certain inorganic cell-constituents accelerates the velocity of reaction between quinone and glycine, but does not increase the temperature coefficient.

5. The bactericidal power of picric acid and potassium permanganate, as well as the quinones, is greatly increased by rise in temperature: and there would appear to be some other factor common to all these disinfectants associated with their high temperature coefficient.

1. An investigation of ninety-eight cases of aseptic meningitis admitted to hospital resulted in the isolation of ECHO virus Type 6 from fifty-one patients.

2. The viruses were cultivated in both human embryonic skin-muscle tissue and human amniotic cell tissue. The latter was found to be more satisfactory.

3. Forty-eight strains were isolated from the stools of patients, six from the cerebrospinal fluid and four from throat-washings.

4. Serological examination of patients from whom the virus was isolated showed that a significant proportion of patients exhibited a specific antibody response. This included three out of six patients with the virus in their cerebrospinal fluid.

5. The clinical picture of aseptic meningitis from which cases ECHO virus was isolated cannot be distinguished from that caused by other known viruses.

6. The evidence presented supports the claim that ECHO virus Type 6 is one of the causes of aseptic meningitis.

Grateful appreciation is acknowledged to Prof. P. M. Holst (Oslo), Prof. Johs. Böe (Bergen), Dr B. Helland-Hanssen (Molde), Dr O. Römcke (Drammen), Dr R. Tingstad (Namsos), and Dr A. H. Brinchmann (Bærum), for providing specimens and case records. I am also grateful to Mrs B. Zapffe and Mrs L. Kohmann for expert technical assistance.

Choline-binding proteins (CBP) have been associated with the pathogenesis of Streptococcus pneumoniae. We screened, using PCR, for the presence of genes (cbpA, D, E, G) encoding these proteins in 34 isolates of pneumococci of known serotypes and penicillin susceptibility from invasive and non-invasive disease. All isolates harboured cbpD and cbpE whereas cbpA and cbpG were found in 47% and 59% respectively; the latter were more frequent in vaccine-associated types and together accounted for 77% of these isolates. No association was observed with penicillin susceptibility but 85% of non-invasive isolates were positive for these genes.

Many contradictory articles on the infectivity of non-culturable Campylobacter jejuni can be found. We studied the effect of non-culturable C. jejuni in an in vitro assay. To prevent the potential effect of a few culturable bacteria in the non-culturable suspension, INT-407 cells, which mimic the outer cell layer in the small intestines, were exposed to culturable C. jejuni suspensions with or without non-culturable C. jejuni. The number of bacteria adhering to and/or invading INT-407 cells and the IL-8 secretion were measured. No differences were found between bacterial suspensions with or without non-culturable C. jejuni added. These findings show that non-culturable C. jejuni do not adhere to or invade INT-407 cells and do not induce an immune response. As previous studies showed a correlation between the used in vitro assays and the effect in vivo, our study strongly suggests that culturability is a good indicator of the risk for C. jejuni infection.

1. The average lethal dose of fluoracetamide for wild R. norvegicus was found to be 13 mg./kg. of body weight and the LD95, about 43 mg./kg.

2. Wild rats offered bait contatining 0·5, 1 and 2% fluoracetamide, after a period of conditioning, seemed to find it palatable and, on the average, ingested the equivalent of 18–100 LD50's. Warning symptoms appeared in about an hour or longer and included short convulsive spasms.

3. The speed of onset of warning symptoms leading to cessation of feeding was studied in albino rats dosed with the equivalent of 2 LD50's of sodium fluoracetate, zinc phosphide or fluoracetamide. Feeding ceased soonest in the case of sodium fluroacetate. Zinc phosphide gave very variable results, but it is thought that if wild rats had been used, feeding would have stopped nearly as soon as with sodium fluoracetate.

4. It is considered that field trials to compare the efficiency of 1% flouracetamide and 2·5% zinc phosphide, both with ‘prebaiting’, would be well justified.

5. Fluoracetamide at 2% may also prove to be a good alternative to 0·25% sodium fluoracetate as a ‘direct’ poison for controlling rats in sewers.

We are indebted to Miss Y. Larthe and Miss E. J. Taylor who took part in the bioassay and in one of the experiments with the marked rats.

Data on the impact of the recently recommended maternal pertussis vaccination are promising, but still insufficient to universalise this approach. We thus compared the epidemiological data prior to the implementation of this vaccination strategy in Argentina (2012) with the figures reported after 2012. During that 2010–2016 period, two outbreaks occurred, one in 2011 and another in 2016. In the former, the incidence was 6.9/100 000 inhabitants and the case-fatality rate 2.6%. Thereafter, a decline in incidence was detected until 2014. During 2015 and 2016 an increase in the incidence transpired, but this rise was fortunately not accompanied by one in the case fatality ratio. Indeed, in 2016 the case fatality ratio was the lowest (0.6%). Moreover, during the 2016 outbreak, the incidence (3.9/100 000 inhabitants) and the case severity detected in the most vulnerable population (infants 0–2 months) were both lower than those in 2011. Consistent with this pattern, in 2016, in the most populated province of Argentina (Buenos Aires), the case percentage with laboratory-positive results indicating a high number of symptoms (59.1% of the total cases) diminished compared with that detected in the 2011 outbreak without maternal immunisation (71.9%). Using the mathematical model of pertussis transmission we previously designed, we assessed the effect of vaccination during pregnancy on infant incidence. From comparisons between the epidemiological data made through calculations, emerged the possibility that vaccinating women during pregnancy would benefit the infants beyond age 2 months, specifically in the 2–12-month cohort.

An outbreak of SARS-CoV2 infection in a Barcelona prison was studied. One hundred and forty-eight inmates and 36 prison staff were evaluated by rt-PCR, and 24.1% (40 prisoners, two health workers and four non-health workers) tested positive. In all, 94.8% of cases were asymptomatic. The inmates were isolated in prison module 4, which was converted into an emergency COVID unit. There were no deaths. Generalised screening and the isolation and evaluation of the people infected were key measures. Symptom-based surveillance must be supplemented by rapid contact-based monitoring in order to avoid asymptomatic spread among prisoners and the community at large.

Social network characteristics of people who inject drugs (PWID) have previously been flagged as potential risk factors for HCV transmission such as increased injection frequency. To understand the role of the injecting network on injection frequency, we investigated how changes in an injecting network over time can modulate injecting risk behaviour. PWID were sourced from the Networks 2 Study, a longitudinal cohort study of PWID recruited from illicit drug street markets across Melbourne, Australia. Network-related correlates of injection frequency and the change in frequency over time were analysed using adjusted Cox Proportional Hazards and Generalised Estimating Equations modelling. Two-hundred and eighteen PWID followed up for a mean (s.d.) of 2.8 (1.7) years were included in the analysis. A greater number of injecting partners, network closeness centrality and eigenvector centrality over time were associated with an increased rate of infection frequency. Every additional injection drug partner was associated with an increase in monthly injection frequency. Similarly, increased network connectivity and centrality over time was also associated with an increase in injection frequency. This study observed that baseline network measures of connectivity and centrality may be associated with changes in injection frequency and, by extension, may predict subsequent HCV transmission risk. Longitudinal changes in network position were observed to correlate with changes in injection frequency, with PWID who migrate from the densely-connected network centre out to the less-connected periphery were associated with a decreased rate of injection frequency.