Natural aerosols of rabbit pox virus produced by groups of infected rabbits were sampled with a slit and Andersen sampler using an adhesive surface sampling technique (Thomas, 1970). The higher rate of successful recoveries of airborne virus compared with a previous report is believed to be due to the much larger volume of air sampled by this technique and to the processing of the whole of the sample collected by the direct addition of a cell suspension to demonstrate the presence of viable virus.

The serological responses of cattle to inoculation with Brucella abortus and Yersinia enterocolitica type IX were compared. Complete cross-reactions were found in serum agglutination, antiglobulin, complement fixation and Rose Bengal plate tests. The cross-reaction between Br. abortus and Y. enterocolitica IX was confirmed by immunodiffusion tests. Although antibodies specific for each organism could also be detected by immunodiffusion tests with high titre rabbit or bovine sera, these tests were insufficiently sensitive for routine diagnostic use.

A quantitative Rose Bengal plate test, using Rose Bengal stained Br. abortus and Y. enterocolitica IX, was developed which enabled the antibody responses to the two organisms to be differentiated. The specificity of this test was confirmed by cross-absorption experiments and its sensitivity was sufficient to permit evaluation of all bovine sera giving positive reactions to the serum agglutination test.

The spread of Staphylococcus aureus was studied in three general surgical wards of identical design which consisted of a number of separate rooms, and the results were compared with those in the same unit previously studied, in subdivided wards elsewhere and in large open wards.

The nasal carrier rate of Staph. aureus by patients rose during their stay in the ward, but its peak rate was comparable with minimum rates reported in other subdivided wards and was lower than in open wards.

Staphylococcal sepsis rates were lower than in most open wards and were also much lower than those found previously in the same unit when overcrowding was common and each sex had its own ward.

When ten cats were infected orally with undiluted or a 10−1 dilution of virulent feline infectious enteritis (panleucopaenia) virus, all developed severe leucopaenia followed by the development of demonstrable antibody, but none died. Eighteen of 29 cats given a 10−2 dilution of virus died of the disease. Three of the survivors had white blood cell counts of less than 4000 and three had counts between 4000 and 6000 cells. Although the remaining five animals never had individual counts of less than 6000 cells, the geometric means of these counts showed that a marked depression in the leucocyte counts had occurred. All surviving cats developed antibody.

Among the ten cats dosed with either 10−3 or 10−4 dilution of virus, four died of feline infectious enteritis and three developed antibody after falls in the leucocyte counts. It is suspected that low dilutions of feline infectious enteritis virulent virus in cats produce a phenomenon similar to that reported by von Magnus (1954) with influenza virus in eggs.

Leucopaenia is commonly defined as less than 4000 white blood cells/mm.3 of blood. Counts lower than this are usual in cats which either die of the disease or have received large doses of virus; they are less common in cats surviving after administration of diluted virus. Challenge of cats with pre-existing antibody did not provoke a depression in the leucocyte counts.

Calf thyroid tissue cultures were found to be the most sensitive system in detecting virus collected in a large volume air sampler from boxes, where cattle, sheep and pigs infected with A and C strains of foot-and-mouth disease (FMD) virus were housed. It was confirmed with all strains of FMD virus tested that pigs excreted the most virus followed by cattle and sheep, but there was variation between strains, the highest virus recoveries being obtained from animals infected with O1 and C Noville viruses. The results are discussed in relation to outbreaks of foot-and-mouth disease in Great Britain since 1954.

Sampling of human subjects, who had been in contact with animals infected with foot-and-mouth disease (FMD) virus, showed that virus could be recovered from the nose, throat, saliva and from air expelled during coughing, sneezing, talking and breathing. The amounts of virus recovered paralleled those collected with a large-volume sampler and multistage impinger and these findings confirmed that the highest recovery of airborne virus was from infected pigs followed by cattle and sheep. More virus was found in the noses of those examining infected animals than in those operating the samplers, but there was variation between the subjects. In the majority there was a 1·8 log fall in titre by 3·5 hr., but virus persisted in the nose of one subject for 28 hr. Nose blowing or washing the nostrils did not remove virus completely, nor were cloth or industrial masks completely effective in preventing inhalation of virus. It was possible to transmit virus from infected subjects to others on one occasion. No clinical cases of FMD in man resulted from exposure, nor was there any rise in antibody. Use was made of these findings in determining sites of aerosol excretion in animals, and the results are discussed in relation to FMD in man and to the spread of respiratory viruses by the airborne route.

Paired nasopharyngeal secretions were studied in 27 infants infected with respiratory syncytial virus, one taken at onset of illness and one about 7 days later. Both specimens were examined by immunofluorescence and tissue culture for respiratory syncytial virus. In 25 out of 27 (93%) specific fluorescence was still present in cells of the convalescent specimen but was much duller. Virus was difficult to isolate in convalescent specimens; only 8 out of 27 (26 %) proved to be positive. Eight single secretions which were taken late in a respiratory illness were also shown to have this altered fluorescence with absence of virus isolation. Preliminary experiments using antihuman globulin suggest that the findings may be due to the attachment of local secretory antibody to the cells causing ‘blocking’ of staining reaction.

Nasopharyngeal secretions were taken during the acute phase of illness from 30 children admitted to hospital with lower respiratory tract infections. The presence of neutralizing activity in secretions taken at the onset of illness was demonstrated in 11 out of 15 patients (73%) with bronchiolitis caused by R.S. virus, as compared with 4 out of 9 patients (44%) with R.S. virus infections other than bronchiolitis, and 1 out of 6 without R.S. virus infection. Second secretions were taken 7 days later from 10 of the children with R.S. virus infection. Eight of these paired secretions showed an increase of neutralizing activity against R.S. virus. It is suggested that the neutralizing activity, found in secretions taken at the onset of illness, may be a result of previous infection with R.S. virus.

Study was made of the effect of BCG vaccination on the establishment of experimental tuberculous infection in mice. To this end, mice were infected with small quantities of virulent human bacilli administered by the respiratory route. The quantity of bacilli present for inhalation was so controlled as to permit only a finite percentage of unvaccinated animals to become infected. The relative proportion of mice infected by inhaling these small numbers of virulent bacilli was not found to be lowered by prior BCG vaccination. Thus, pulmonary tissue of immunized mice was not able to prevent the initial lodgement of virulent tubercle bacilli. The growth of virulent organisms in infected lungs, however, was significantly retarded by prior vaccination.

The prevalence of salmonellas in drain swabs from three abattoirs of Athens was studied with the use of conventional methods of Salmonella isolation as well as with a new procedure which involves secondary enrichment from the usual selenite broth or Muller-Kauffmann's tetrathionate broth in Rappaport's medium slightly modified.

In all groups studied the secondary enrichment in Rappaport's medium led to an increase in the number of positive swabs, in the number of Salmonella serotypes, and in the total number of strains isolated.

The frequency of Salmonella isolations was higher in samples from abattoirs killing only pigs and lower in samples from abattoirs killing only cattle or only sheep.

The predominant serotype in abattoirs dealing with cattle was Salmonella tennessee, and S. typhimurium in abattoirs dealing with sheep. No predominant serotype was found in samples from abattoirs dealing mostly with pigs.

S. abony, S. drypool, S. emek, S. Indiana, S. muenchen and S. tennessee were isolated for the first time in Greece.

The use of gauze swabs in drains or sewers to clarify the path followed by a salmonella from source to human host has been reviewed in the light of experience gained in Cardiff over 15 years. This period has seen a marked change in attitudes to salmonella epidemiology in that infected food is now regarded as of greater importance than infected food handlers. In these 15 years, butchers, abattoirs and knackers' yards, markets and bakehouses have been monitored. In the bakehouse survey the existence of staff infection was demonstrated by sewage examination. Sewage investigation has also been used to show frequent entry of salmonellas into households in a residential estate. The estate was carefully chosen to exclude salmonellas from industrial sources and shops. The frequent finding of infection in this sewage implies that a commonly consumed heavily infected food item is involved. The wide range of serotypes isolated suggests an animal usually fed on infected animal feed. Poultry and pigs are put forward as animals liable to spread salmonellosis to man.

It is hoped that clarification of the salmonella pathway may eventually lead to measures likely to prevent the transmission of infection to man. It is also suggested that swabs placed in abattoir drains serve as an economical method of obtaining warning of a persistent build-up of contamination. The persistence of a serotype in an abattoir is not infrequently followed by human infection.

Coxsackie A 6 virus, strain V 29, originally isolated from Aedes polynesiensis in Fiji, was found to survive in A. australis for 5 days after intrathoracic injection and for 6 days after feeding on viraemic mice, and in Culiseta tonnoiri for 8 days after feeding.

The virus level in both fed and injected mosquitoes fell steadily after infection and never exceeded the original level.

No virus transmission was obtained in 46 successful second feedings on days 10–14 with A. australis, but three transmissions were obtained with C. tonnoiri, two on day 10 and one on day 13, from 12 successful second feedings.

A 10-month follow-up of 14 Fijian children suffering from molluscum contagiosum showed that the condition could last from about 6 months to about 3 years, but that any one lesion was present for only 2 months. There could be temporary relief from new lesions for at least 2 months; when complete remission occurred, it could be comparatively rapid. It is suggested that individual lesions should not be treated, in order to avoid scarring and because of their relatively rapid disappearance.

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.

All respiratory illnesses which were reported to the medical officers between September 1966 and December 1967 on a Royal Air Force station of 350 men were studied virologically.

Three periods of increased respiratory infections were observed: two occurred in the autumn, one in each year, and the third in the winter during January and February. The autumnal outbreaks were associated mainly with rhinovirus infections, and high isolation rates (82·1, 65·9%) were achieved at these times. Few of the illnesses during the winter outbreak could be diagnosed in the laboratory, and no evidence was found of infection with ‘coronaviruses’.

Despite the entrance of 30 fresh recruits direct from civilian life every 5 weeks, the respiratory infections encountered on the station were very similar to those in the local population and were not predominantly infections with adenoviruses, Coevirus, and Mycoplasma pneumoniae, as previously reported from larger military recruit centres.

An epidemic of acute respiratory disease in a colony of CFE rats is described, the main laboratory findings are recorded and its aetiology discussed.

The epidemic showed that severe respiratory disease varying from peracute to chronic was associated with infection of the lungs with a mycoplasma but that mycoplasmas could be present in rats, even in the lungs, without signs of disease, thus suggesting that one or more other factors were involved. It is also evident that there are strain differences in the susceptibility of rats to this disease.

Nine hundred and seventeen Salmonella infections in 580 households were confirmed during a laboratory study of diarrhoea in general practices in a large urban area during the years 1953–68. This was an annual incidence of about 2/10,000 population. Salmonellas were found in nearly 2% of new cases of diarrhoea investigated. Plural infections were found in 36% of the households studied and 18% of all contacts examined were shown to be infected. Among these contacts the infection rate was higher for children (24%) than for adults (16%). The duration of infection was longer than 2 months in nearly a quarter of the cases followed up, and intermittent excretion was observed in one-fifth. The commonest serotype was Salmonella typhimurium, but its incidence in the district declined especially after 1964. S. typhimurium infection provoked a severer enteritis but less general symptoms than did other salmonellas. Children were more susceptible than adults to salmonella infection, to illness and to prolonged excretion, but symptoms in index cases were as severe in adults as in children.

Daily observations were made on the excretion of African swine fever (ASF) virus by pigs infected intranasally or by contact. Two strains of virus having mean death times of approximately 3 and 6 days were used, the latter being recently isolated from a warthog.

First excretion usually occurred by the nasopharyngeal route, as early as 1 or 2 days before the onset of fever in many cases. The titres of pharyngeal and nasal swabs rose rapidly to reach mean levels of about 104–106 HAD 50 at 48–72 hr. following the onset of pyrexia. Virus in the secretions of the conjunctiva or lower urogenital tract appeared later and did not attain such high levels. Faecal and urinary excretion was of relatively little significance, except in slower infections caused by the recent warthog virus.

These results are discussed in relation to the known failure of infected pigs to transmit the disease to stallmates during the first 12–24 hr. of pyrexia and also in relation to recent work on the pathogenesis of ASF in domestic swine.

There are situations in which direct observation of the attachment of antibody molecules may be the simplest method of detecting antigen-antibody reactions. Applied to the study of the sex pili determined by a number of transmissible bacterial plasmids, the method has distinguished four serotypes in the F-like class and two in the I-like class. Antibody was usually attached haphazardly to the pili; however, in a few cases a regular periodicity could be observed. When few antibody molecules were attached, they could frequently be individually resolved and in certain antibody-pilus combinations large antibody molecules, tentatively identified as IgM, could be seen to predominate.