Laboratory aspects of a programme of sewer swabbing during and after the Aberdeen typhoid fever outbreak, 1964, have been described. Results were discussed and reasons suggested for the relative insensitivity of methods employed in the isolation of Salmonella typhi. It was tentatively concluded that generalized sewer swabbing in a large city was not likely to be very helpful in tracing undetected excreters of S. typhi during and immediately after a major typhoid fever outbreak. The cost of the laboratory side of this investigation, for staff salaries, equipment, media, etc., was somewhat over £7000.

The authors wish to express thanks to Dr I. A. G. MacQueen, M.O.H., Aberdeen, and his staff including Mr H. B. Parry, Chief Sanitary Inspector and staff, for willing and helpful co-operation throughout this programme. Grateful acknowledgement is also made to Dr B. Moore of the Public Health Laboratory, Exeter; to Dr E. S. Anderson of the Enteric Reference Laboratory, London, for ‘phage typing’ the numerous isolations and to Dr Joan Taylor of the Salmonella Reference Laboratory, London, for assistance in typing Salmonella spp. isolated. Especial thanks are due to our laboratory technicians and other staff for the willing support given during the investigation.

Live type 4 adenovirus contained in enteric-coated tablets was given to 2628 military recruits. In two trials, the enteric adenovirus vaccine reduced febrile and afebrile adenovirus illness by about 90% or more. Moreover, a decided protective effect against subclinical adenovirus infection as evidenced by seroconversion was found.

The antibody-stimulating effect of enteric adenovirus vaccine was not an adequate measure of its protective capacity. The neutralizing antibody response of recruits given vaccine was poor in comparison with the antibody response to naturally acquired infection with type 4 adenovirus. The latter response was related to the severity of infection.

We are indebted to Colonel Dr B. J. W. Beunders, Head of the Division of Preventive Medicine of the Royal Netherlands Army, for granting us facilities to conduct this study and to Misses W. T. C. J. Smulders, E. M. J. C. Vallas, J. E. M. Dusseldorp and M. M. J. P. Keeris for their valuable technical assistance.

Genetic marker tests were performed on 61 strains of poliovirus isolated during the Blackburn outbreak from cases or suspected cases and their contacts. The results were correlated with the epidemiological data and good agreement was found for the serological and dextran inhibition tests. The reproductive capacity temperature marker, however, showed inhibition at 39·8° C. of strains otherwise judged to be of naturally occurring type. These strains could be differentiated from those of vaccine origin because they grew readily at 39·2° C. This feature also distinguished the strains isolated in Blackburn from those obtained in the nearby town of Hyde in a simultaneous outbreak.

Dr J. Ardley, Medical Officer of Health, Blackburn, kindly provided a key which enabled the contacts of cases to be traced; and Dr L. Robertson, Public Health Laboratory, Preston, made available his extensive records as well as the many strains isolated in his laboratory.

Two hundred and sixty-four samples of sera obtained from normal healthy persons belonging to different age groups were examined for haemagglutination-inhibiting antibodies against reovirus types 1–3 to assess the prevalence of reovirus infection in the northern part of India.

Reovirus infection appeared as early as 6 months to 1 year of age. With reovirus types 1 and 2, the maximum incidence of 67 and 48% respectively occurred by the age of 10–20 years, whereas with type 3 infection the maximum incidence (73%) was reached by the age of 25 years. The incidence of reovirus type 2 infection in all the age groups was remarkably low in this series. A drop in the incidence of reovirus type 2 infection was also noticed after the age of 20 years.

The difference in geometric mean titre of antibody in different ages against reovirus type 2 was highly significant, suggesting probably that most of the infection occurred by the age of twenty years. The difference in the geometric mean value of the titres of antibody against types 1 and 3 was not significant in different age groups. The levels of antibody against types 1 and 3 in all the age groups were almost the same, suggesting that infection, specially with reovirus type 3, was occurring in all the age groups even beyond 20 years of age.

The authors wish to express their sincerest thanks to Dr Leon Rosen, Pacific Research Section, National Institute of Allergy and Infectious Diseases, Honolulu, Hawaii, for the supply of prototype strains of reoviruses, to Drs B. K. Aikat, Director Professor of Pathology, R. N. Chakravarti, Department of Experimental Medicine, O. N. Bhakoo, and Sucheta Thukral, Department of Paediatrics, Post- Graduate Institute of Medical Education and Research, Chadigarh, for their invaluable help and co-operation, to Prof. P. V. K. Iyer, Department of Mathematics, Panjab University, and to Mr H. D. Gupta, Biostatistician, Post-Graduate Institute of Medical Education and Research, Chadigarh for their statistical analysis of the results.

The authors gratefully acknowledge the helpful criticism and suggestion of Dr C G. Pandit, Ex-Director, Indian Council of Medical Research, during the preparation of the paper.

The authors acknowledge also the technical assistance of Mr Jagmohan Lai Pipat, Mr Gurmeet Singh Khatra, and Mr Amar Singh Saini.

This work was partly supported by the Research Grant of the Indian Council of Medical Research sanctioned to one of the authors (S. R. P.).

The purpose of surveys of amoebae or other organisms is the estimation of the carrier rate in a population, that is, of the proportion of persons who carry a given parasite. As a rule, the tests do not infallibly detect the presence of the organism in a known carrier. Thus simple estimation from a single examination of each member of a sample is not applicable.

Evidence was presented to support a hypothesis that competition between antibody molecules can be an important factor in vaccinia virus neutralization.

It has been shown that there is little difference in the virus neutralizing properties of 7 S and 19 S antibody and it has been further postulated that in the context of protective immunity the proportions of antibodies having neutralizing and interfering effects is likely to be more important than the absolute concentration of neutralizing antibody or the type of immunoglobulin in which it is present.

Plaque neutralization on HEp 2 cells was used to determine the relationship between vaccinia, rabbitpox, cowpox and ectromelia using both 7 S and 19 S antibody. It was shown that for the strains of virus used vaccinia and rabbitpox were very similar but cowpox and particularly ectromelia were clearly distinguishable. The cross-titration relationships were the same for 7 S and 19 S antibody.

The titration slopes and kinetics of cross-neutralizations were interpreted on the basis of a hypothesis of antibody competition put forward in the preceding paper. It was tentatively concluded that these four viruses share a common critical antigen for neutralization and that differences in the structure or presentation of neighbouring antigens could give rise to some of the observed effects.

Poliovirus type 1, strain LSc2ab, was directly sprayed in a static air cabinet at 20° C. and sampled afterwards with impingers. Virus inactivation during spraying was maximal in dry air; during storage maximal decay occurred at moderate humidity.

With regard to the mechanism of the inactivation the following facts have been observed: (1) The RNA in the virus decays simultaneously with the whole virus particle. (2) Oxidation does not play any significant role. (3) Incubation with L-cystine protects the virus against inactivation at 50° C. in aqueous suspension, but not against decay in aerosols.

On the strength of these observations it is concluded that in aerosols denatura-tion of the viral RNA is the cause of the inactivation of poliovirus. The decay in aerosols has some features in common with the thermal inactivation in aqueous suspensions at room temperature.

An investigation was carried out into the bacteriological performance of three air-conditioning plants in a hospital ward. Two of these plants had the facility for recirculating part of the ward air.

An equation has been derived comparing the concentration of bacteria which would be expected to be given off by the humidifiers in the ventilation system, with the concentration of bacteria in the recirculatory tank. The bacterial particles given off by these humidifiers were of nuclei droplet size, and were found to penetrate the filters used with a fair degree of ease. Although the number of bacteria in the humidifier water remained insignificant with a constant overflow of water into the recirculatory tank, on one occasion a build-up of bacteria was demonstrated when the overflow ceased. For hospital use humidifiers of a non-recirculatory type should be used.

The concentration of bacteria on the surface of the recirculatory ducts was assessed, as also were those on the surface of the supply ducts under full fresh air and recirculation. The concentration of bacteria in the supply ducts was low and the use of terminal filters was not merited, although care should be taken to prevent the build-up of bacteria in inlet grills and diffusers. The bacterial concentration in the exhaust ducts was found to be quite high. It was therefore thought that in critical areas, where the ventilation plant may be shut off, the use of some device to prevent reversed air flow may be necessary.

The count of various types of micro-organisms in the fresh air and two-thirds recirculated air are given along with their size distribution. The results of the effect of filtration on the concentration of bacterial particles throughout the air-conditioning plant is given under full fresh air and recirculation. These concentrations appear quite satisfactory. It was found that one set of filters had been overgrown by mould because of free water being brought over from the humidifier. Measures have been suggested to overcome this. When primary or prefinal filtration was approximately 90% efficient to Aloxite 50 (B.S. 2831 Test Dust no. 2) it was demonstrated that a fair approximation to the final filtration figure could be obtained by reference to the quoted efficiency of the final filter to Aloxite 50. After similar primary filtration it was demonstrated that the final filtration of filters against recirculated and fresh air was approximately the same. Owing to the higher number of Staph. aureus in recirculated air, higher efficiency filtration may be required.

Standards of filtration efficiency for critical and non-critical zones are suggested.

Four cows were inoculated via the udder with the 1836 strain of Mycoplasma bovigenitalium. The serological response was investigated using the complement-fixation and serum plate agglutination tests. A heterologous response to M. mycoides was observed, associated with an increase in the anti-γ-globulin titres in the cow's serum. The heterologous response persisted in one cow for 6 weeks after infection. The nature of the immunoglobulin response was characterized by density gradient centrifugation, and by mercaptoethanol and rivanol treatment of the serum and was found to consist entirely of 19 S γ-globulins.

The Mycoplasma persisted in the udder for the 18 weeks duration of the experiment. The Mycoplasma was not isolated from the blood. One of the cows became lame with swollen joints; Bacillus cereus was isolated from the joints and blood.

Two strains of enzootic pneumonia, which are regularly free from mycoplasmas other than Mycoplasma suipneumoniae, were transmitted experimentally to a total of 22 pigs. M. suipneumoniae was recovered in liquid medium from the lung lesions in 20 of these animals (91%).

Twelve field outbreaks of enzootic pneumonia were likewise examined for M. suipneumoniae: from each outbreak, cases were selected where many mycoplasmas with the morphology of M. suipneumoniae were seen in touch preparations made from the lung lesions. M. suipneumoniae was recovered from only two of these outbreaks, but M. hyorhinis was obtained from nine of them.

To establish whether the outbreaks yielding only M. hyorhinis were indeed enzootic pneumonia, material from five of them was used in disease-transmission experiments: enzootic pneumonia was induced in every instance, and M. suipneumoniae was recovered from three of the five transmitted strains.

It is concluded that M. hyorhinis is commonly present in the lung lesions of enzootic pneumonia and that this mycoplasma may often prevent the isolation of M. suipneumoniae. The problem of recovering M. suipneumoniae in this situation is made more difficult by the fact that in no instance where M. suipneumoniae was isolated directly in liquid medium was it cultured in parallel on solid medium.

As many cultures of Staph. aureus untypable by the international basic-set phages at RTD were typed by a block of 20 extra phages at RTD as by the basic set at RTD × 1000. Reproducibility of the lytic patterns was as good with the extra phages at RTD as with the basic-set phages at RTD, and better than with the basic-set phages at RTD × 1000.

A method of assessing redundancy in any set of phages is presented, and a ‘3-strong differences’ rule is suggested for discriminating between cultures of staphylococci from patterns of phage lysis by the combined set of phages at RTD.

Experience with the combined set of phages suggests that it may be possible to improve the phage-typing of staphylococci by substituting a larger series of phages used only at RTD, for the present set of 22 phages used at RTD and RTD × 1000.

A cylinder filled with medium is described, with which prints are made of floors or other surfaces. After a print has been made a slice is cut off the medium, put in a Petri dish and incubated. With one filled cylinder about twenty prints can be made. The method can be used for quantitative bacteriological testing of floors, and the effect of treatment with disinfectants can also be checked in a simple way. Preference was given to disinfection with Halamid.

Sheep infected with FMDV strains of different epizootiological origin developed a carrier state which persisted in the majority of animals for 1–5 months.

The sites of virus persistence and multiplication in the convalescent animal were identified by titration of suspensions of mucosae and epithelia taken post mortem. Virus was recovered most frequently and in highest titre from the tonsillar area and less frequently from the pharynx and dorsal surface of the soft palate. No virus was found in samples taken from the nasal passages, the trachea or the rumen.

In nine laboratories 1% lactose ricinoleate broth has been investigated as a possible alternative to brilliant green bile broth as a confirmatory medium for coliform organisms and Escherichia coli.

Although the results varied considerably from one laboratory to another, in the sum of the results and in the majority of the participating laboratories 1% lactose ricinoleate produced fewer false negative reactions than brilliant green bile broth as a confirmatory medium at both 37 and 44° C.

Although both media are satisfactory, 1% lactose ricinoleate broth can be recommended as an alternative to brilliant green bile broth for the confirmation of coliform organisms and Esch. coli from presumptive positive tubes in the examination of water samples, as it is not subject to the known variability of brilliant green and ox-bile.

This article describes an outbreak of Q fever involving 24 men (five prison officers and nineteen detainees) in one of H.M. Detention Centres. The evidence collected points strongly to the consumption of raw milk as the route of infection. This appears to be the first milk-borne outbreak of Q fever to be reported in Britain.

The recent epidemic of acute glomerulonephritis in Trinidad had two peaks, separated by an interval of about 6 months.

Evidence is presented that there were in fact two successive but overlapping epidemics, the first due to streptococci of provisional M-type 55, and the second to streptococci of M-type 49.