1. Sixteen cases of paralytic poliomyelitis and twenty-four cases of aseptic meningitis (‘non-paralytic poliomyelitis’) occurring in the Sheffield area were studied clinically and by virological methods.

2. Poliovirus was isolated from thirteen of the sixteen cases of paralytic poliomyelitis and from three of the twenty-four cases of aseptic meningitis. In another two of the cases of paralytic poliomyelitis and another six of the cases of aseptic meningitis serological evidence of poliovirus infection was obtained.

3. Serological evidence of Coxsackie virus infection was found in four of the cases of aseptic meningitis; but in one there was also clear-cut evidence of poliovirus Type 3 infection, and in another it seemed that the infection was contracted in hospital. Evidence of Coxsackie virus infection was also obtained in five cases of paralytic poliomyelitis.

4. Serological evidence of Adenovirus infection was found in one case of aseptic meningitis.

5. No acceptable evidence was found of infection with Columbia SK or related viruses, or with the virus of lymphocytic choriomeningitis.

6. From one patient with aseptic meningitis an unidentified virus was isolated.

We wish to thank Dr J. Kennedy for permission to study patients and Prof. C. P. Beattie and Prof. C. H. Stuart-Harris for help in preparing the manuscript.

Eleven cases of aseptic meningitis occurred in a Cambridgeshire village between 17 October and 11 November 1955. The syndrome consisted of severe headache, backache, vomiting, fever and neck stiffness together with lymphocytes and frequently some granulocytes in the cerebrospinal fluid. Principally, it affected persons aged between 10 and 30 years. Out of a total population twenty-three at risk, seventeen were infected and eight became ill. A further three contacts who were living in Cambridge became ill.

Identical strains of virus were isolated from the faeces of two patients by inoculation of trypsin-dispersed human amnion cells and from the faeces of another two patients by inoculation of monkey kidney cultures. Bourn virus, which belonged to the ECHO group, Type 9, multiplied readily and produced cytopathogenic effects in human amnion and monkey kidney cultures, but it was not cytopathogenic in HeLa cell cultures. These investigations strongly suggest that Bourn virus caused the epidemic.

We wish to thank Dr M. G. P. Stoker for his advice and criticism and Mrs B. M. Cook for technical assistance.

We are indebted to Dr J. O'H. Tobin and Dr F. K. Sanders for advice on certain technical procedures.

It is a pleasure to acknowledge the assistance given by many colleagues and friends, including Dr D. I. Annear, Miss D. K. Bell, Mrs D. Ditchburn, Dr R. M. Fry, Dr D. Gairdner, Dr J. E. Power, Dr D. Simpson, Dr P. Tyzer and Dr P. J. Wormald.

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.

Sera of Nigerians aged between 10 and 60 years were tested individually for their antibody to five strains of influenza A virus. The results showed a similar pattern to those which other investigators have found with sera collected in the U.S.A. and in this country. However, antibody to the swine and WS strains was found in younger individuals than was reported previously; and the distribution of antibody titres suggests that this represents antibody to minor antigens of more recent strains, rather than persistence of swine and WS viruses.

We should like to thank Dr C. H. Andrewes F.R.S. for his criticisms and Dr James S. Porterfield who sent the sera.

Calculations have been carried out which indicate that poliovirus vaccine contains sufficient antigen to account for the observed antibody response.

Ninety-seven groups of five-membrane pock counts from 115 titrations of vaccinia virus preparations were examined in an attempt to identify the statistical distribution followed by such counts, and to obtain an estimate of the overall coefficient of variation of the technique.

It was found that the distribution of counts was neither Poissonian nor normal, and that the count variances ‘wandered’ so extensively that no valid estimate of the overall coefficient of variation was possible. Nor was it possible to assess the intrinsic reproducibility of the test, although it is empirically a useful one.

A study has been made of various factors involved in performing neutralization tests with vaccinia virus on chorio-allantoic membranes.

The common practice of using a single serum concentration has been shown to result in a test which is qualitative only. The linear relationship between the logarithm of the pock count of the surviving virus and the logarithm of the serum dilution can be used to determine the dilution of serum which will neutralize 50% of a virus suspension. By this method it is possible to distinguish between sera whose potencies vary by about fourfold.

I gratefully acknowledge the advice and criticism given by Dr J. C. N. Westwood and Dr I. A. Macpherson, as well as the help given by Mr S. Peto with the statistical treatment of results. My thanks are also due to Mr H. B. Maber and Corporal M. Fitzpatrick, R.A.M.C., for their technical assistance.

In seeking a more satisfactory test than the conventional mouse-protection tests for the assessment of typhoid-paratyphoid vaccines in relation to their O and Vi antigens, it was decided to undertake a series of experiments with vaccines containing the somatic antigens of Salmonella paratyphi C and to use this organism to challenge mice thus immunized. Salm. paratyphi C contains the same Vi antigen as Salm. typhi and moreover it is capable of giving rise to a true infection in mice in contrast to the acute intoxication which follows a fatal dose of Salm. typhi.

Large doses, of the order of 100 × 106, of this paratyphoid organism injected intraperitoneally into mice resulted in acute intoxication with death in 24–72 hr., similar in every way to the picture with typhoid bacilli, but when the dose was reduced 100-fold or more an infective illness was set up which after an interval of 5–10 days or more, during which the organisms multiply freely in the tissues, terminated fatally. Typhoid bacilli do not produce a true infection in mice.

Living vaccines were prepared of Salm. typhi Ty6S (an almost pure Vi strain) and Salm. cholerae-suis (contains the same O-antigen complex as Salm.paratyphi C). These were used separately, and in combination, to immunize different batches of mice by the subcutaneous route against a subsequent intraperitoneal challenge with a Vi-positive culture of Salm. paratyphi C at both high- and low-dose levels. The different challenge doses were to assess the relative values of the 0 and Vi components in protecting against intoxication (high dose) and infection (low dose), respectively.

Against intoxication pure Vi vaccines were almost as effective as Vi + O vaccines, whereas pure O vaccines gave little or no protection.

Against fatal infection the combined Vi + O vaccine offered good protection and the pure O vaccine was but little inferior, whereas the pure Vi vaccine appeared to be without significant effect.

Quite small doses of Salm. paratyphi C administered by the intra-gastric route can give rise to a general infection in mice, but in order to obtain consistent results much larger doses were found necessary (about 300 x 106 organisms). Mice immunized with the same three vaccines and subsequently challenged by the intragastric route with this large dose showed significant protection throughout. The combined, O + Vi, vaccine did not appear to have any advantage over the pure O vaccine, but both were markedly superior to the pure Vi vaccine. Further experiments on the same lines are however necessary to see if the results obtained in this single experiment are reproducible.

The relationship of the above findings to the evaluation of agents employed in man for the prophylaxis of enteric fever and the need for further experimental work of a similar nature are discussed.

We wish to thank Dr F. Kauffmann for strains of Salm. paratyphi C, Lt-Col. T. E. Field, whose results we have freely quoted, and Dr S. Peto for advice on statistical evaluation of our results.

1. When GDVII virus was injected into the brains of mice, subsequent intracerebral injections of mixed pertussis and diphtheria prophylactic significantly shortened the incubation period. Subsequent intramuscular injections of mixed prophylactic had no influence on the course of the infection.

2. Intramuscular inoculation of either GDVII virus or EMC virus results in a marked localization of paralysis in the injected limb. With GDVII virus, the localization probably arises from the use of the sciatic nerve route for entry into the c.n.s., and is unaffected by injection of substances into the opposite limb. With EMC virus, localization can be modified by injections into the opposite limb.

3. When GDVII or EMC virus was injected by a peripheral route other than intramuscular, intramuscular injections of vaccines or normal mouse brain suspension induced localization of paralysis in the injected limb.

4. Intramuscular inoculation of vaccines increased mortality in mice injected into the same limb muscle with GDVII virus. Within the limits tested the later the vaccines were injected relative to the virus, the greater was the effect.

5. When the vaccines used were more than a few months old, this facilitating effect was replaced by a protective effect. Mice injected intramuscularly with aged vaccines were significantly more resistant than the controls to GDVII virus injected into the same muscle.

6. Intracerebral inoculation of vaccines, and to a lesser extent other substances, increased mortality in mice which had received intramuscular inoculations of GDVII virus, by allowing virus to pass directly from the blood into the brain. This resulted in a predominance of cerebral symptoms when the vaccines were injected immediately after the virus, but not when the interval was lengthened to 48 hr.

7. The mode of action of modifying factors in neurotropic virus infections is discussed in the light of these results.

This work was done in the Department of Zoology, Oxford University, during the tenure of a grant from the Medical Research Council. I also wish to thank the Nuffield Foundation for their support of the virus research carried on in the Department.

I am most grateful to Dr F. K. Sanders for his advice and criticism, as well as for provision of technical facilities, and to Dr Donald Michie for assistance with the statistical treatment of the data, and for much other help.

1. The electrostatic precipitation of single cell bacterial aerosols has been studied. Two types of electrostatic precipitators of the wire-in-tube construction have been developed. In one type the collector is a tube with nutrient agar, in the other a vertical water-film.

2. Collection efficiencies of 90 % and more could be obtained at sampling rates of 25 l./min. and tensions varying from 5 to 10 kV.

3. The survival of organisms in electrostatic precipitators has been measured in comparison with other samplers, viz. the slit sampler, membrane filters and impingers. The equivalence of the electrostatic precipitators and other samplers in sampling spore aerosols could be demonstrated. Aerosols containing vegetative organisms were sampled equally well in the agar tube precipitator as in the slit sampler. In the precipitator with water-film collector there is a loss of c. 25 % of viable cells.

4. The practical advantage of the electrostatic precipitators is their very low air resistance.

The authors feel greatly indebted to Prof. Dr J. A. Cohen and Dr F. Wensinck for their helpful criticism of the manuscript, to Mr W. de Vries who designed and constructed the generator for extremely high tension; to Mr R. van Strik, Philips-Roxane (Weesp, Netherlands), for statistical advice and computations and to Miss H. Kranenburg for technical assistance.

1. The relationship has been examined between the variance and the mean of pock counts made by a number of different workers.

2. In all cases the variance was considerably greater than that expected if the distributions were of the Poisson form. Recent work of Westwood et al. (1957) suggests that variation approaching the Poisson expectation can be achieved by appropriate technical measures.

3. With one exception, there appeared to be a linear relationship between the logarithm of the variance and the logarithm of the mean. The slope of this line varied from one laboratory to another, but not, apparently, from one occasion to another in any one laboratory.

4. The hypothesis that for any set of egg membranes the expectations of the pock counts bear constant ratios to each other, irrespective of the virus density, was untenable: the observed variances increase less rapidly with high counts than would have been expected on this theory.

5. Statistical methods are proposed for comparing and combining sets of counts at different dilutions. If Poisson variability were achieved, simpler methods would be available.

I am much indebted to Dr L. Collier, Prof. A. W. Downie, Dr C. Kaplan and Dr F. O. McCallum for permission to use their unpublished data; to Dr J. C. N. Westwood for discussing with me his (then) unpublished work; to Miss Irene Allen for computing assistance; and to Mrs G. M. Young for the preparation of the diagrams.