Two cyclones for sampling dilute aerosols in the field are described. Their advantages are their robustness and reliability, the high degree of concentration achieved, and the ease with which they will provide a long uninterrupted sequence of samples.

Methods of correcting estimates of cloud concentration for transfer lag in the cyclone are derived.

The cyclones were constructed by J. Nott. We are indebted to G. J. Harper and E. J. Morris for allowing us to make use of their observations, and to Dr J. S. Paterson (Superintendent, Allington Farm) for providing the realistic aerosol at our convenience.

Pseudorabies virus (PrV) infections appear to be more widely distributed in the European wild boar (Sus scrofa) population than assumed. In Europe, attempts to isolate and characterize the causative agents have been limited so far. We therefore collected and examined a total of 35 PrV isolates obtained from wild boar or hunting dogs in Germany, France, Spain, Italy, Slovakia and Hungary between 1993 and 2008. Restriction enzyme analysis of genomic DNA using BamHI showed that all isolates, except one, belonged to genogroup I but different subtypes were evident. For further investigations of the phylogenetic relationships, a 732-bp fragment of the glycoprotein C (gC) gene was amplified by PCR. Sequence analysis revealed about 40 variant positions within this fragment. Comparison of the nucleotide sequences supported the separation into a clade containing isolates from North-Rhine Westphalia, Rhineland-Palatinate (Germany), France and Spain (clade B) and an apparently more variable clade comprising isolates from Brandenburg, Baden-Wurttemberg, Saxony, Saxony-Anhalt (Germany), Slovakia, Hungary, Italy and France (clade A).

The analysis of contact networks plays a major role to understanding the dynamics of disease spread. Empirical contact data is often collected using contact diaries. Such studies rely on self-reported perceptions of contacts, and arrangements for validation are usually not made. Our study was based on a complete network study design that allowed for the analysis of reporting accuracy in contact diary studies. We collected contact data of the employees of three research groups over a period of 1 work week. We found that more than one third of all reported contacts were only reported by one out of the two involved contact partners. Non-reporting is most frequent in cases of short, non-intense contact. We estimated that the probability of forgetting a contact of ⩽5 min duration is greater than 50%. Furthermore, the number of forgotten contacts appears to be proportional to the total number of contacts.

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.

Seven different flotation fluids were assessed for their efficiency in recovering Toxocara canis ova from artificially seeded soil samples. Using the most efficient (a saturated solution of magnesium sulphate plus 5 % potassium iodide) 25 g amounts of 234 environmental soil samples were examined for the presence of Toxocara spp. and Toxascaris ova. Twenty-six samples (11·1 %) yielded ova of one or other species. There was no discernible pattern of distribution of positives with relation to the source of the samples. The maximum number of ova recovered in any one sample was 19. All the ova recovered from the environment were considered viable and potentially infective.

‘Mention of a trademark or a proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture, and does not imply its approval to the exclusion of other products that may also be suitable.’

Non-immunized, vaccinated, and recovered cattle were inoculated intranasally with various doses of foot-and-mouth disease virus. Samples of oesophageal-pharyngeal (OP) fluid were taken periodically for up to 7 days after inoculation and virus titres of these samples were plotted as pharyngeal virus growth curves.

In non-immunized cattle, the length of the lag period and of the growth period were inversely proportional to the dose of virus given. Maximum titres were observed when clinical signs were first detected. Three of the 10 cattle studied had virus growth rates that were lower than rates of others given the same dose of virus, and clinical signs appeared later than expected in these three cattle.

Cattle vaccinated with an inactivated virus oil-adjuvant vaccine had pharyngeal virus growth curves that were similar to those obtained from non-immunized cattle for 30 h. after inoculation. Titres of virus in OP fluid samples taken 2–7 days after inoculation were substantially lower in cattle with a high pre-exposure serum mouse protection index than titres from partly-immunized or non-immunized cattle.

Nine of 14 recovered cattle had detectable but reduced virus growth after intranasal inoculation with homologous virus. Five recovered cattle inoculated with heterologous virus reacted similarly to non-immunized animals.

A large outbreak of campylobacter enteritis associated with the consumption of free school milk is described. The outbreak had an abrupt onset, and lasted for about 3 weeks; it involved mainly school children in the 2–4 and 5–7 year old age groups. During this period it was established from epidemiological and microbiological data that some 2500 children were infected. The source of the epidemic was almost certainly contaminated milk, although bacteriological proof could not be obtained. Biotyping of isolates was of considerable epidemiological value and showed the involvement of two distinct strains, one of which was dominant. Epidemiological evidence of limited person to person transmission of the infection was obtained; febrile convulsions as a prodromal sign of the illness was recognized for the first time. Strains of Campylobacter jejuni, and samples of patients' serum collected during this outbreak have enabled subsequent studies to be initiated on the serotyping of the responsible organism, on the serological response of patients infected with the organism, and on experimental infection of the bovine udder which demonstrated its potential as a source of C. jejuni in raw milk. A careful search of the literature suggests that this is the largest documented outbreak of campylobacter enteritis.

Current methods to establish the duration of toxoplasma infection in pregnant women and for the diagnosis of toxoplasmosis in the neonate or HIV infected patient have significant limitations. We assessed the precision of a commercial ELISA for the detection of toxoplasma specific IgG and adapted the assay to measure avidity using an elution agent washing step. The sensitivity and specificity of the ELISA were 100 and 75 % respectively and optimal measurement of avidity was achieved using 6 M urea as the elution agent.

Toxoplasma lymphadenopathy of less than 3 months duration was associated with low avidity specific IgG but some discordant findings were recorded. Serial measurement of IgG avidity assisted the distinction between actively produced antibody in infants with congenital toxoplasmosis and passively acquired antibody of maternal origin in uninfected babies. There was no significant difference between avidity levels in HIV infected patients with or without cerebral toxoplasmosis.

We provide an update on the epidemiology of shigellosis in Israel using data generated by a sentinel laboratory-based surveillance network for the period 1998–2012. The average annual incidence of culture-proven shigellosis was 97/100 000. We estimated that each case of shigellosis accounted for 25 cases in the community indicating the high burden of disease. Orthodox Jewish communities, living in highly crowded conditions and with a high number of children aged <5 years were the epicentre of country-wide biennial propagated epidemics of S. sonnei shigellosis. S. flexneri was the leading Shigella serogroup in Israeli Arabs. S. flexneri 2a and S. flexneri 6 alternated as the most common serotypes. Both S. sonnei and S. flexneri isolates showed high rates of resistance to ampicillin and trimethoprim/sulfamethoxazole and very low rates of resistance to quinolones and third-generation cephalosporins. Shigellosis due to S. sonnei conferred 81% (95% confidence interval 69–89) protection against the homologous Shigella serotype when epidemic exposure re-occurred 2 years later. These data are of value in the process of Shigella vaccine development.

Escherichia coli O157 outbreaks were identified in Minnesota in February 2003 involving seven persons and in Colorado in July 2003 involving 13 persons. Case isolates from the two states had matching pulsed-field gel electrophoresis (PFGE) patterns. Independent case-control studies linked infections in each outbreak with eating alfalfa sprouts that were traced to the same seed distributor. The Colorado sprouter reportedly complied with the Food and Drug Administration (FDA) sprout guidance, whereas the Minnesota sprouter did not. These investigations revealed that increased compliance with existing FDA guidance is needed and that additional research is needed to improve the alfalfa seed decontamination process. This reaffirms the FDA recommendation that raw alfalfa sprouts should be considered potentially contaminated and avoided by persons at high-risk such as the elderly, young children, and immunocompromised persons. PFGE played an essential role in linking these two temporally and geographically distinct E. coli O157 outbreaks.

Salivary excretion of rabies virus was evaluated in 14 adult vampire bats (Desmodus rotundus) intramuscularly injected with a large dose (106 MICLD50) of vampire rabies virus variant CASS88. Saliva samples were obtained from surviving bats every other day for 30 days, then weekly for 2 months, and finally 1 and 2 years later. Rabies virus was isolated in murine neuroblastoma cells and in randomly selected cases by PCR. Rabies virus was not detected in the saliva of any of the 11 animals that succumbed (somewhat early) to rabies challenge, nor in the control bats. In contrast, virus was detected early, and only once (days 6, 6 and 21) in each of the three animals that survived rabies challenge and remained healthy for at least 2 years after challenge. At that time even vigorous dexamethasone and cyclosporine administration failed to provoke further viral excretion.

Six patients developed local infection after being bitten or groed by swine. Wounding was often deep and occurred characteristically on the posterior aspect of the thigh. Severity of infection caried from simple wound infection with discharge and slouth to cellulitis and abscess formation; pathogens included haemolytic streptococci, pasteurellae, Bacterodies sp., Proteussp. and Escherichia coli and were usually isolated in mixed culture. A patient with Pasteurella aerogences infection apperars to be the first reported in England. A seventh patient developed Streptococcus milleri septicaemia after wounding himself while cutting teeth from piglets. It is suggested that a course of broad-spectrum antibiotics should be given as part of the initial treatment when patients present with the more servere pig bite injuries.

1. During the years 1954–56 large number of salmonellae, comprising six sero-types and a number of Salm. typhi-murium phage types, were isolated at the Bradford abattoir.

2. Most of the cultures were derived from pigs; the animals presented no sign of clinical illness.

3. Human salmonella infections in Bradford over the same period were closely related to the abattoir findings.

4. It seems probable that individual pigs are infected on the farms and when brought to the abattoir may infect others in the lairages.

5. Limiting the duration of stay in the lairages and prevention of overcrowding may substantially reduce the proportion of animals found infected at slaughter.

We wish to express our thanks to Dr John Douglas, Medical Officer of Health, Bradford, for his interest and encouragement in this investigation and to Mr F. H. Myres, Mr J. Noble, Mr E. Root and Mr R. Butterfield of the Bradford Health Department for their enthusiastic help. Thanks are also due to Dr Joan Taylor and Dr E. S. Anderson and staffs of the Salmonella and Central Enteric Reference Laboratories, Colindale, for their assistance in typing Salmonellae, and to a number of our colleagues who have kindly read the script and offered valuable criticisms.

Certain fimbriae and the flagellae of Salmonella enterica serovar Typhimurium have been shown to contribute to attachment and invasion of gut epithelium in the murine typhoid infection model and to contribute to pathogenesis in the chick. However, little is known of the role these organelles play in Enteritidis poultry infections and, to study this, day-old chicks were dosed orally in separate experiments with defined multiply afimbriate and/or aflagellate mutant strains of Enteritidis. The colonization and invasion characteristics of each mutant were compared with those of the isogenic wild type strain by the determination of the number of bacteria recovered from livers and spleens at known time points post infection. Compared with wild type Enteritidis, a mutant unable to express flagella but retaining the genetic potential to express fimbriae was recovered post mortem from livers and spleens in significantly reduced numbers compared to the isogenic wild-type at all time points post infection (P<0·001). Conversely, a flagellate but multiply afimbriate mutant (defective for the elaboration of five different fimbrial types) and a flagellate but non-motile ‘paralysed’ mutant were recovered from livers and spleens in similar numbers to the wild-type. The data suggested that Enteritidis flagella, but not fimbriae, played an important role in pathogenesis in the chick model and that the flagellar apparatus itself and not motility per se contributed significantly to this role.

Legionella pneumophila is the main pathogen responsible for outbreaks of Legionnaires' disease, which can be related to contaminated water supplies such as cooling towers or water pipes. We combined conventional molecular methods and whole genome sequence (WGS) analysis to investigate an outbreak of L. pneumophila in a large Australian hospital. Typing of these isolates using sequence-based typing and virulence gene profiling, was unable to discriminate between outbreak and non-outbreak isolates. WGS analysis was performed on isolates during the outbreak, as well as on unlinked isolates from the Public Health Microbiology reference collection. The more powerful resolution provided by analysis of whole genome sequences allowed outbreak isolates to be distinguished from isolates that were temporally and spatially unassociated with the outbreak, demonstrating that this technology can be used in real-time to investigate L. pneumophila outbreaks.

The outbreak of pneumonia-like respiratory disorder at China and its rapid transmission world-wide resulted in public health emergency, which brought lineage B betacoronaviridae SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) into spotlight. The fairly high mutation rate, frequent recombination and interspecies transmission in betacoronaviridae are largely responsible for their temporal changes in infectivity and virulence. Investigation of global SARS-CoV-2 genotypes revealed considerable mutations in structural, non-structural, accessory proteins as well as untranslated regions. Among the various types of mutations, single-nucleotide substitutions are the predominant ones. In addition, insertion, deletion and frame-shift mutations are also reported, albeit at a lower frequency. Among the structural proteins, spike glycoprotein and nucleocapsid phosphoprotein accumulated a larger number of mutations whereas envelope and membrane proteins are mostly conserved. Spike protein and RNA-dependent RNA polymerase variants, D614G and P323L in combination became dominant world-wide. Divergent genetic variants created serious challenge towards the development of therapeutics and vaccines. This review will consolidate mutations in different SARS-CoV-2 proteins and their implications on viral fitness.

The prevalence of campylobacter gastroenteritis has been estimated by bacterial isolation using selective culture. However, there is evidence that certain species and strains are not recovered on selective agars. We have therefore compared direct PCR assays of faecal samples with campylobacter culture, and explored the potential of PCR for simultaneous detection and identification to the species level. Two hundred unselected faecal samples from cases of acute gastroenteritis were cultured on modified charcoal cefoperazone deoxycholate agar and subjected to DNA extraction and PCR assay. Culture on CCDA indicated that 16 of the 200 samples contained ‘Campylobacter spp.’. By contrast, PCR assays detected campylobacters in 19 of the 200 samples, including 15 of the culture-positive samples, and further identified them as: C. jejuni (16), C. coli (2) and C. hyointestinalis (1). These results show that PCR offers a different perspective on the incidence and identity of campylobacters in human gastroenteritis.

A collection of 308 clinical isolates of β-haemolytic Lancefield group C streptococci was assembled from laboratories in England. Nigeria and New Zealand. Of these, 276 isolates were Streptococcus equisimilis. 23 S. milleri and nine S. zooepidemicus. Isolates of S. equisimilis in the African collection, though few, gave higher rates of lactose and raffinose fermentation, aesculin hydrolysis and positive α-galactosidase reactions than those from elsewhere. Erythromycin resistance was found in 1·9% of the English isolates of S. equisimilis.Strains from superficial infections accounted for 88 % of the collection and were most commonly isolated from the upper respiratory tract, skin or wounds. Amongst the 36 patients yielding isolates from deep sites S. equisimilis was found in septicaemia, cellulitis, abscess, peritonitis, septic arthritis, pneumonia, mycotic aneurysm and acute epiglottitis. S. milleri was found in abdominal abscesses, peritonitis, pleural empyema and osteomyelitis and S. zooepidemicus was found in septicaemia, pneumonia, meningitis and septic arthritis. Within the collection an unselected general catchment of 214 isolates of group C streptococci from the laboratories in Yorkshire showed the following species: from 199 superficial infections 94% S. equisimilis. 5% S. milleri and 1% S. zooepidemicus and 15 patients withdeeper, more agressive infections 67, 27 and 6·7% of these species respectively.

In a 5-year retrospective survey of respiratory syncytial virus (RSV) infections among hospitalized children, 1340 cases were identified of which, 98·4% were children <5 years old with a male:female ratio of 1·5:1. Most cases occurred from April to September showing a significant positive correlation with temperature and relative humidity. Community-acquired infections accounted for 92·5% of the cases with a mean hospital stay of 5 days. The estimated annual incidence of RSV infection requiring hospitalization was 2·5/1000 children <5 years old with a mortality of 0·15% among hospitalized cases. On average, 248 children were admitted each year to the 1400-bed acute regional hospital accounting for an expenditure of HK $1.94 (∼US $0.25) million for hospitalization costs which equates to an annual cost in excess of HK $6.67 (∼US $0.86) million for the whole of Hong Kong. An RSV vaccine should be a priority.

Following primary vaccination no antibody was detected up to the tenth day. After this time neutralizing antibody and antihaemagglutinin were present in the majority of individuals, while, with the technique used, complement-fixing antibody was found in less than half those examined. Neutralizing antibody may be found in the blood more that 20 years after primary vaccination; by this time very few show antihaemagglutinin and then only in low titre. Complement-fixing antibody was not found more than 6 months after primary vaccination.

In revaccinated individuals the antibody response tended to be higher than after primary vaccination and, when it occurred, often appeared within a week. This suggests that prompt revaccination of smallpox contacts may offer even greater protection than does primary vaccination.

The neutralization test is a better measure of immunological response than are either of the other two tests, for these may give a negative result even though there may be a well-marked rise in neutralizing antibody. The ‘early’ type of reaction to revaccination was associated with an antibody response in only about half the subjects examined. In the remainder, the skin reaction, although identical in appearance, must be regarded as allergic in nature and not accompanied by increase in immunity.