Attempts were made to demonstrate variola virus in the conjunctival exudate of 84 smallpox patients who developed conjunctivitis in the acute stage of the illness or during convalescence. Variola virus was isolated from 60 but not from the remaining 24. Of the 64 from whom virus was isolated the conjunctivitis developed from the onset up to the 15th day of illness. From conjunctivitis developing later virus was not recovered. In some patients who developed conjunctivitis early in the disease we failed to recover virus from the conjunctival exudate.

Of 55 close family contacts who stayed in hospital with smallpox patients four developed smallpox. In 21, conjunctivitis but no other illness developed. From 12 of these, variola virus was recovered from the conjunctival exudate and four of these 12, who were further investigated, showed after the appearance of conjunctivitis antibody titres similar to those seen in typical smallpox cases. From nine of the contacts who developed conjunctivitis virus was not recovered. One of these had antibody titres in serum collected before the onset of conjunctivitis which indicated recent smallpox infection. In another there was a marked antibody rise during her hospital stay although examination of conjunctival exudate on three separate occasions failed to yield variola virus. Twenty-six family contacts who developed no illness in hospital had antibody determinations made on sera collected soon after admission to hospital. In eight of these antibody titres were such as to indicate recent smallpox infection although there were no signs, in the form of scarring, or history of recent smallpox infection. These findings have been discussed in relation to the occurrence of minimal and subclinical infection in close family contacts of smallpox patients.

This investigation was supported in part by Public Health Service Grant AI–1632–16 VR from the National Institute of Allergy and Infectious Diseases, by the World Health Organization and by the Marcus T. Reynolds III Fund.

A survey of 13 linen chutes in eight hospitals was carried out to assess the amount of bacterial contamination on the inner walls of these chutes. It was shown that the average bacterial count in these chutes was low by general hospital standards (19·7 bacterial colonies per Rodac plate). This concentration was eight times less than the average concentration found on the floor surface at each linen disposal and collection point (153 bacterial colonies per Rodac plate).

Three chutes sampled during the survey were periodically cleaned but appeared to derive only very limited benefits from the cleaning method they used.

Tests carried out on three linen chutes showed that the bacterial surface contamination of a sterilized chute could normally reach a maximum concentration in a period of between 4 and 24 hr.

It is concluded that so long as good engineering practices are used in the construction of linen chutes the bacterial contamination on their inner surface should not contribute to the problem of hospital cross infection. For this reason, and because of the impracticability of sterilizing linen chutes at very short intervals of time, it is considered that cleaning of chutes would serve no practical purpose.

Thanks must be recorded to the authorities of all those hospitals who gave their permission for us to study their linen disposal chutes and afforded us every assistance.

We should also like to thank Mr W. Carson, Leader of the Building Services Research Unit, for his help and encouragement.

The work reported was a part of an investigation into the design of linen disposal chutes sponsored by the Western Regional Hospital Board, Scotland.

The degree of protection provided by various air movement control systems, as applied to isolation and treatment rooms, has been assessed. The main factors influencing the efficiency of isolation were the air supply rate to the room and the time the door was left open. The effect of some other possible factors, such as temperature differences and method of air distribution, are discussed.

The type of facilities provided must depend on the type of patient and economics, but prediction equations, which allow the assessment of positive, negative and balanced ventilation systems, are presented. The ventilation requirements for isolation rooms should be assessed individually, but for a treatment room a balanced system of ventilation with between 500 and 1000 ft.3/min. should be very effective. Precautions should be taken to ensure the air quantities are balanced and temperature differences are minimized. An air lock should not be necessary for balanced systems provided these rooms are in a mechanically ventilated ward.

We thank Mr W. Carson and members of the Building Services Research Unit for their help and advice and Sister M. F. D. Muir and the staff of the experimental ward for their co-operation. This work was sponsored by the Nuffield Provincial Hospitals Trust.

Requests for reprints, or a fuller description of the ward unit and test results, should be addressed to George Baird, Building Services Research Unit, 3 Lilybank Gardens, Glasgow, W. 2.

The relationship of pre-operative nasal and skin carriage of Staphylococcus aureus to wound colonization and sepsis was studied in 269 patients. Thirty-seven per cent of 96 carriers developed wound colonization as compared to 16 % among non-carriers (a statistically significant difference). The wound sepsis rates were 17 % and 9 % respectively. The combination of nasal and skin carriage was an important factor, since the sepsis rate among skin carriers (most of whom were nasal carriers as well) was 22%. Among carriers, the homologous strain was recovered from the majority of wound colonizations and from all instances of wound sepsis. A carrier strain also was recovered from 52% of the wounds colonized and from 50% of septic wounds in the entire study group. Profuse nasal carriage resulted in a significantly greater number of septic wounds (31%) than sparse carriage (9%). Wound cultures before closure, and skin from the initial incision site only once yielded a patient's carrier strain or a strain of Staph. aureus that was later recovered from the wound. The results indicate that measures designed to control the carrier state or to isolate the wound from the external environment should reduce wound sepsis by approximately one half.

Excellent technical aid was furnished by Eleanor Ford, R. N., Edith E. Silverman, Adrienne Marus, M. S., and Patricia Welch.

A modification of the Henderson apparatus is described which is mobile and which can produce bacterial or viral aerosol in air whose relative humidity can be chosen in the range 20–95 %. The apparatus forms a basic utility for microthread, rotating drum or other aerosol studies.

Much help and advice has been given by Messrs. J. F. H. Peel and D. J. Garriock of the Engineering Section M.R.E. throughout the development of this apparatus. The proportioning valve is a modification of one originally used for a similar purpose by Mr K. R. May. Thanks are due to Messrs. G. J. Harper and A. M. Hood for criticism of the script.

Secondary schoolchildren in England were asked to assess thermal conditions in winter according to subjective sensations of warmth. Conditions of normal occupancy and activity were maintained and optimum conditions established in terms of four thermal measures by regression analysis of over 2500 assessments by boys and girls. The comfort zone was delineated as that within which 60% of the children were comfortable and in terms of the commonly used dry-bulb temperature this zone lay between 59 and 70° F. in still air. The optimum conditions for children were also compared with those recommended for adults.

White pock mutants of cowpox virus produce pocks in the CAM which ‘mimic’ those produced by the parent virus, in macroscopic and microscopic appearance, and in the amount of virus they contain. The proportion of such ‘atypical’ pocks was influenced by the age and source of embryo, incubation temperature and position of the CAM during incubation. Similar results were obtained with white pock mutants isolated from strains of vaccinia, rabbitpox and monkeypox. The appearance of pocks produced by variola, alastrim, ectromelia and vaccinia (Lister) was unaffected by changes in environmental conditions.

I would like to thank Professor K. McCarthy, Professor K. R. Dumbell, Dr C. H. Taylor-Robison and Dr C. R. Madeley for their interest and for kindly providing virus strains, and Miss M. Seyfang for technical assistance.

I would like to thank the Committee on Research, Liverpool University, for a grant towards the cost of the colour plate.

Mice which carried the tapeworm Hymenolepis nana gave anomalous results when they were infected with tubercle bacilli. Males died earlier than females. The cause of death in some was intussusception or acute enteritis. More tapeworm eggs were excreted in the faeces of male mice, and, for each sex, egg counts were higher in BCG-vaccinated animals.

This work forms part of the studies on immunity to tuberculosis for a Ph.D. thesis, and was carried out while I was in receipt of a Harrison-Watson Studentship of Clare College and a Welcome Fellowship of the Animal Health Trust.

Salmonella senftenberg was isolated from 168 patients and staff of a general hospital whereas it was isolated from only seven other sources (four of which were unquestionably associated with the hospital) in the surrounding area during the same period. It was isolated in the hospital in 19 of the 48 months of the period. Two clear-cut episodes were recognized against a background of sporadic isolation. Four-fifths of the patients and staff excreting the organism had no symptoms. Only two are known to have been severely ill, though in some patients very ill for other reasons life may have been shortened a little.

The original source of the organism, whether from the farm or from raw materials such as meat or poultry, was not found.

Mice immunized with a fraction from a culture filtrate of Ps. aeruginosa, then burned and infected with virulent serotypes of Ps. aeroginosa, were protected from septicaemia and death.

The immunogenic fraction killed mice at dosages 400 times those of the minimum protective dosages.

Treatment of the immunogenic fraction with 0·5% formalin reduced its lethal effect for mice and slightly improved its immunizing potency so that the difference between the smallest immunizing dose used and the smallest amount that killed mice was more than 80,000 doses.

After a single subcutaneous injection into baboons the MRC-4 strain of trachoma/inclusion conjunctivitis (TRIC) agent underwent limited multiplication at the injection site, but was then eliminated rapidly from the skin and regional lymph nodes. Forty-eight hours after a single intravenous injection, but not thereafter, it appeared in the peripheral lymph nodes and spleen. The single parenteral injections failed to immunize baboons against conjunctival challenge with the homologous strain. These findings contrasted with those previously reported for the more virulent mutant, MRC-4 f, which multiplied readily in the skin, lymph nodes and spleen, persisted in these tissues up to 3 weeks after injection, and conferred good immunity to conjunctival challenge with MRC-4. The difference in behaviour of MRC-4 and MRC-4 f might be accounted for, at least in part, by the use of a smaller inoculum of live MRC-4; but similar findings in guinea-pigs, reported elsewhere, suggest that the differences observed are real. In conjunction with previous work, the present study suggests that the immunogenicity of TRIC agent is closely related to the mass of antigen that can be administered to or propagated within the recipient.

We are grateful to Mr D. Venters for his able technical assistance.

Studies were made of a 14-room isolation ward in which the bedrooms were provided with individual ventilation units to provide a slight positive pressure within the rooms. Airborne staphylococci were detected with sedimentation plates.

The median count of Staphylococcus aureus in the occupied bedrooms was 4·6 col. per 14 cm. plate exposed for 24 hr. or 13 col./m.2 hr. When the air count was high virtually all the staphylococci proved to be of the phage type harboured by the patient in the room; with low counts a substantial proportion were apparently derived from patients in other rooms.

The apparent rate of acquisition of S. aureus in the nose of the patients was between 2·7 and 4·2 per 100 patient weeks at risk. This is substantially lower than has commonly been observed in open wards.

We are very graetful to Miss M. A. Adams, Sister in charge of the Almroth-Wright isolation Ward, and all her staff for all their help and co-operation during this study, which was supported by funds provided to St Mary's Hospital by the Ministry of Health for clinical research.

The reconstruction of the ward was designed by Mr A. Stableford, Group Engineer to St Mary's Hospital; the ventilation units were designed and supplied by White Bays and White Ltd., London.

In view of recent food-borne outbreaks of salmonella infection in which cooked-meat slicing machines have been implicated in the spread of organisms from contaminated meat products to other meats, experiments have been made to provide laboratory evidence that a contaminated slicing machine will easily cross-contaminate other products passing through it. Chopped pork inoculated with coagulase-positive staphylococci was cut on a slicing machine; staphylococci were isolated up to the 41st slice of various cooked meats cut on the same machine. The experiments were repeated with Salmonella oranienburg; this serotype was isolated up to the 31st slice of various cooked meats cut on the same machine, and from pieces of damp cloth wiped over the gravity feed, knife centre disk and cutting blade.

The importance of efficient and regular cleaning of slicing machines with hot water containing detergent/disinfectant, or detergent followed by disinfectant, applied with clean cloths or preferably disposable paper, is stressed.

I thank Dr Betty C. Hobbs, Director of the Food Hygiene Laboratory, and Dr J. C. Kelsey, Administrative Director of the Central Public Health Laboratory, for their help throughout the work and the compilation of the paper.

Two new media, strontium chloride and strontium selenite broths, are described for the enrichment culture of Salmonella from human and animal material.

In comparative trials, strontium chloride was found to be comparable to Rappaport medium for the recovery of a wide range of Salmonella serotypes from human faeces and sewage, and from pig faeces and glands. Both were superior to selenite F medium.

Strontium selenite was found to be superior to selenite F in the recovery of S. typhi from human faeces and sewage.

We are greatly indebted to Mr M. H. Lello for preparing the samples of strontium selenite used in the investigation and for allowing us to publish the notes on his method of preparing the substance.

Our thanks are due to Pro. C. T. Huang of Hong Kong for sending samples of faeces from typhoid cases under his care; and to Dr Joan Taylor for her continuing help in confirming or identifying the serotypes of salmonella isolated.

We thank Dr W. S. Davidson, Commissioner of Public Health, Western Australia, for permission to publish.

Nasopharyngeal secretions and cough/nasal swabs were taken from 111 children admitted to hospital in Newcastle upon Tyne with acute lower respiratory disease. A comparison was made between nasopharyngeal secretions and cough/nasal swabs as material for isolation of viruses in tissue culture. These results were, in turn, compared with those obtained by applying a fluorescent antibody technique to the exfoliated cells in the nasopharyngeal secretions for the rapid diagnosis of respiratory syncytial virus infection.

More viruses were isolated in tissue culture from nasopharyngeal secretion than from cough/nasal swabs. Further evidence for the superiority of nasopharyngeal secretions was obtained by comparing the virus isolations in the laboratory in 1967 with those in 1968. Respiratory syncytial virus was not only isolated more often but more quickly in tissue culture inoculated with nasopharyngeal secretions.

The fluorescent antibody technique not only provided a diagnosis on the patient's day of admission in 95% of those infected with respiratory syncytial virus but also proved to be as sensitive as the culture of nasopharyngeal secretions and considerably more sensitive than the culture of cough/nasal swabs for the diagnosis of respiratory syncytial virus infection.

We wish to acknowledge the invaluable help given us by consultants, medical officers, ward sisters and their staff in the paediatric wards of the Child Health Department. We also wish to thank the technical staff in the Department of Virology for their aid.

Serum specimens collected in 1966 from individuals of different age groups were studied for the presence of haemagglutination inhibition (HI) antibody to four influenza viruses. All sera were from individuals of blood group A or O and in no instance was the incidence of antibody to a virus strain significantly greater for persons of blood group O compared with similar aged individuals of blood group A. This finding for HI antibody to A 2/Singapore/1/57 is different from similar studies of serum specimens collected in 1961–3. It is suggested that the change in the immune status of a population, with reference to blood-group status, is due to repeated exposure to infection; this changing pattern of immune status is discussed.

Similar studies of HI antibody to adenovirus type 3 and 7 in human sera from persons of blood group A and O shows a changing pattern with increasing age. These results are consistent with the findings for influenza virus and are discussed. Repeated exposure of a population to infection results in obscuring genetically determined variations in susceptibility.

I would like to thank Professor M. G. McEntegart, Professor of Medical Microbiology, and Professor C. H. Stuart-Harris, Professor of Medicine, for their advice and criticism, and Miss D. Coles, F.I.M.L.T., and Mrs P. Robinson for expert technical assistance.

It was possible to demonstrate from retrospective records that a link existed between contaminated animal feedstuffs, turkeys and an outbreak of Salmonella senftenberg infection at Ryhope Hospital. Possibly infected or contaminated turkeys were supplied to the hospital from two turkey farms in one of which the birds were fed on contaminated white fish meal and the other had had infected birds.

This work was carried out months after the events described and would not have been possible without the help and co-operation of the Public Health Laboratory Service, The Veterinary Field, Investigation and Research Services, Houghton Poultry Research Station, The Medical Officer of Health for Brighton, Dr Rosetta Parker, and the various feed companies involved, who very kindly made their records available to us.

A large-volume sampler was used to recover virus excreted as aerosol by cattle, sheep and pigs infected with foot-and-mouth disease. Pigs were found to excrete virus to a maximum of 104.7 ID 50 per animal per hour and sheep and cattle to a maximum of 103.2 ID 50. Excretion from pigs totalled 106 ID 50 per animal over 5 days and from cattle and sheep 3 x 104 ID 50 per animal over 4 days. Maximum recovery occurred 41 hr. after infection in pigs and cattle when lesions had generalized and 17 hr. after infection in sheep before lesions had been observed. Sampling in a multistage liquid impinger showed that 65–71% of virus was excreted as an aerosol of size > 6 μ, 19–24% 3–6 μ and 10–11% less than 3 μ. The site of production of virus excreted as aerosol is suggested to be the upper respiratory tract. Under conditions of relative humidity greater than 70% and at low temperatures, survival of virus to a distance of 100 km. is likely to occur and because of the minute respiratory volume the aerosol would be sampled more efficiently by cattle than pigs or sheep and by large animals than by small. These findings are discussed in relation to spread of virus in the field.

Mr Dave Allen and Massey-Ferguson Ltd. are thanked for their generous donations, with which the large-volume sampler was purchased. We are grateful to Dr C. E. Gordon Smith, Mr G. J. Harper and Dr K. P. Norris of the Microbiological Research Establishment, Porton, for advice and help and for the loan of the multistage liquid impinger. The technical assistance of N. H. Cheale and C. W. Hawkins is gratefully acknowledged.

Investigations to define the epidemiological pattern of adenovirus infection in military recruits were carried out in a training centre at Ossendrecht, The Netherlands, during a 9-year period. Extensive outbreaks of adenovirus illness occurred in the winter and spring, and in some years in the late fall. The seasonal variation in total incidence of adenovirus infection as estimated by frequency of antibody rises in randomly selected recruits correlated well with that of adenovirus illness. In the cold season 20–60 of every 100 men were infected, whereas no or very little activity of adenovirus was found during the summer.

Type 7 was prevalent during the first 2 years of the study period, type 21 during the next 3 years and type 4 during the last 4 years. The proportion of adenovirus infection associated with clinical illness, the distribution of adenovirus illness by week of training and the immunity of incoming recruits against adenovirus infection as estimated by frequency of neutralizing antibody were compared for type 7, type 21 and type 4.

Adenovirus was responsible for about one third of all cases of acute respiratory illness. The next most common diagnostic category was influenza. Other respiratory agents (parainfluenza, RS and Coxsackie A-21 viruses, Mycoplasma pneumoniae and haemolytic streptococci) were of less importance.

This work was supported in part by the United States Department of the Army through its European Research Office.

We are indebted to the following persons who contributed to this study: C. P. A. van Boven, R. Brouwer, J. H. E. Custers, J. H. Dijkman, A. Prins and A. R. van der Werff, medical officers; Mr A. P. K. M. I. van Nieuwstadt, Miss M. C. J. van Nunen, Dr G. C. J. van der Ploeg and Dr H. J. A. Sonderkamp, members of the staff of our laboratory; and Misses C. H. Bronswijk, G. J. Hof, A. D. E. M. Leeuwenberg, W. T. C. J. Smulders and C. M. G. Stevens, and Mrs A. M. van Snik, technicians.

Major-General Dr H. J. van der Giessen and Brigadier General W. P. Blokpoel, former Directors-General of Medical Services of the Royal Netherlands Army, and Colonel Dr B. J. W. Beunders, former Head of the Division of Preventive Medicine, granted facilities for the conduct of this study.

Hysterectomy-produced, colostrum-deprived pigs were injected twice with formalinized antigen prepared from the J strain of Mycoplasma suipneumoniae; the first injection was with Freund's adjuvant and the second injection without adjuvant. The immunity of these animals was tested by inoculating them intranasally with different doses of lung suspension prepared from cases of enzootic pneumonia. Two of the pigs were not killed shortly after infection, but were kept and challenged with enzootic pneumonia in order to compare the serology of experimentally-injected animals with the serology of the immune state following the experimentally-induced disease.

In a second main experiment, a pregnant sow was injected twice with nonformalinized antigen without adjuvant, and her litter was subsequently exposed to the disease at 7 days of age after suckling naturally from birth.

There was no evidence to suggest that the injections had protected the pigs in the first experiment against a high dose of infection, but they may have given some protection against low doses. The piglets suckled by the injected sow were not protected against two different doses of infection.

Serum samples taken at different stages were examined by the metabolic inhibition (MI) test, the indirect-haemagglutination (IHA) test, the complement fixation (CF) test and the gel-diffusion precipitin test, using M. suipneumoniae as antigen.

Serum samples taken before injection in the first experiment were all negative in the MI test and they became positive after the injections of antigen. However, 1 the highest MI titres obtained were not associated with obvious immunity; nor was the development of true immunity after experimental infection associated with a change in MI titre.

In the first experiment, substantial IHA titres (over 20,000) were recorded by 14 days after the second injection of antigen. Again, there was no correlation between the IHA titres and the area of pneumonia following experimental infection. In the sow experiment, IHA titres developed after the first injection and increased after the second; a high IHA titre occurred in the colostrum and titres of 320 or more were present in the piglets 7 days after birth.

The CF titres appeared earlier than the IHA titres but did not increase so markedly thereafter. Once more, there was no correlation between the titre before infection and the area of pneumonia afterwards.

In the gel-diffusion test, precipitins were demonstrated in all the post-injection serum samples tested, most of the samples being positive after the first injection. Precipitins were also demonstrated in the colostrum of the injected sow and in her uninjected litter at 7 days of age.

From these experiments it was concluded that, as judged by the development of pneumonic lesions and in marked contrast to the known immunizing effect of the disease itself, injections of antigen given in this manner had little or no protective effect against the dose levels of infection used. Nevertheless, the titres obtained in the MI, IHA and CF tests were comparable with those obtained earlier in pigs that were strongly immune, which provides further evidence for the suggestion that these tests do not measure protective immunity.

Miss Elaine Repworth provided technical assistance. Most of the expenses of this work, including the salary of two of the authors (R. G. H. and R. L. W.) were met by a grant from the Agricultural Research Council.