In a paper on “The Spread of Bacterial Infection” (Journal of Hygiene, xix. No. 4, March 22, 1921) Dr W. W. C. Topley has shown the results of many months' observation of the progress of an epidemic in a population of mice. The author thus describes the experiment: “This experiment lasted from May 21, 1919, until June 11, 1920.…The epidemic started about the middle of October, 1919, and continued in the manner to be described until the conclusion of the experiment.…The period May 21 to September 17 is omitted.…During this time there was no indication of the active spread of infection.…The whole experiment may be divided roughly into four periods. The first extends from May 21 to Sept. 17, and has been referred to already. From Sept. 18 and onwards, only normal mice were added to the cage. From this date until Jan. 5, 1920, the mice were added in such a way as to keep the total number in the cage roughly constant. From Jan. 6 to April 27, 1920, three normal mice were added each day, except on two occasions when none was added. The number of mice in the cage during this period varied from day to day, reaching a maximum immediately before each considerable wave of mortality, and falling to a minimum just before its cessation. During the final period from April 28 to June 11, 1920, two normal mice were added daily instead of three.”

During the past four years it has been part of our routine work to examine samples of ground waters from wells and springs in various portions of Ohio, and, in so doing, organisms have been obtained from time to time conforming to the tests usually given as differentiating faecal bacteria.

There is limited research on whether inequalities exist among individuals from different ethnicities and deprivation status among enteric fever cases. The aim of the study was to investigate the association between the enteric fever incidence rates, ethnicity and deprivation for enteric fever cases in England. Additionally, it was assessed if ethnicity and deprivation were associated with symptom severity, hospital admission and absence from school/work using logistic regression models. Incidence rates were higher in the two most deprived index of multiple deprivation quintiles and those of Pakistani ethnicity (9.89, 95% CI 9.08–10.75) followed by Indian (7.81, 95% CI 7.18–8.49) and Bangladeshi (5.68, 95% CI 4.74–6.76) groups: the incidence rate in the White group was 0.07 (95% CI 0.06–0.08). Individuals representing Pakistani (3.00, 95% CI 1.66–5.43), Indian (2.05, 95% CI 1.18–3.54) and Other/Other Asian (3.51, 95% CI 1.52–8.14) ethnicities had significantly higher odds of hospital admission than individuals representing White (British/Other) ethnicity, although all three groups had statistically significantly lower symptom severity scores. Our results show that there are significant ethnic and socioeconomic inequalities in enteric fever incidence that should inform prevention and treatment strategies. Targeted, community-specific public health interventions are needed to impact on overall burden.

A total of 289 non-O1 Vibrio cholerae (NVC) strains and 20 rough V. cholerae (RVC) strains isolated in an endemic area were tested for antibiotic resistance and for transferable R-plasmids. Twenty three per cent of NVC and 40% of the RVC isolates were found to be resistant to one or more drugs. Eight NVC and four RVC strains possessed multiple drug resistance, varying from four to eight drugs. The common spectrum found in NVC isolates were chloramphenicol and streptomycin (CS) or chloramphenicol, streptomycin, tetracycline and ampicillin (CSTA). Resistance to sulphamethoxazole (Su) and to trimethoprim (Tm) was encountered infrequently. In RVC isolates in addition CSTASuTm determinants, resistance markers to aminoglycosides kanamycin, gentamicin and neomycin were also found. Eighteen of the 27 V. cholerae strains with two or more resistance determinants transferred them en bloc to Escherichia coli K12. The level of resistance in the recipient strain was equal to or greater than that of the donor vibrio strains. Most of the strains possessing solitary resistance markers were unable to transfer them. βlactamase production could be demonstrated in 92·8% of the ampicillin resistant strains. None of the strains was resistant to nalidixic acid or furazolidone. The results emphasize the importance of antimicrobic susceptibility determination of V. cholerae isolates, regardless of the serotypes, before commencing chemotherapy.

Less than half of stool samples from people symptomatic with infectious intestinal disease (IID) will identify a causative organism. A secondary data analysis was undertaken to explore whether symptomology alone could be used to make inferences about causative organisms. Data were utilised from the Second Study of Infectious Intestinal Disease in the Community. A total of 844 cases were analysed. Few symptoms differentiated individual pathogens, but grouping pathogens together showed that viral IID was more likely when symptom onset was in winter (odds ratio (OR) 2.08, 95% confidence interval (CI) 1.16–3.75) or spring (OR 1.92, 95% CI 1.11–3.33), the patient was aged under 5 years (OR 3.63, 95% CI 2.24–6.03) and there was loss of appetite (OR 2.19, 95% CI 1.29–3.72). The odds of bacterial IID were higher with diarrhoea in the absence of vomiting (OR 3.54, 95% CI 2.37–5.32), diarrhoea which persisted for >3 days (OR 2.69, 95% CI 1.82–3.99), bloody diarrhoea (OR 4.17, 95% CI 1.63–11.83) and fever (OR 1.67, 95% CI 1.11–2.53). Symptom profiles could be of value to help guide clinicians and public health professionals in the management of IID, in the absence of microbiological confirmation.

A strain of Proteus vulgaris, recovered from a case of cystitis, showed extreme pleomorphism in a primary culture on ordinary agar.

Pleomorphism was not found in sub-cultures on media free from added NaCl, but it appeared in the presence of a limited range of NaCl concentrations; with still higher concentrations it was not observed, although growth occurred. It was rarely found in cultures which grew with difficulty.

Pleomorphism, occurring under the conditions mentioned as to salt concentration, was most marked in young cultures which grew vigorously; it usually disappeared as the cultures aged; and it became less and less evident in serial sub-cultures on medium containing the same amount of salt.

The morphology of the organism differed on different media, e.g. filamentous on salt-free agar, short bacillary on MacConkey's agar, but it was practically constant in repeated sub-cultures on any one type of medium.

Pleomorphism could be re-induced on any of the media used by suitable alteration of its NaCl content (increase or decrease). Pleomorphism was not determined by variation of the H-ion concentration of salt-free media; nor by variation of the temperature of incubation of cultures; nor by growth in fluid media as opposed to solid media.

After nearly 4 years under laboratory conditions the organism is still sensitive to variation in the NaCl concentration of its environment, as evidenced by pleomorphism; but pleomorphism is now less extreme than it was originally.

Pleomorphism is still most marked in young sub-cultures on media with suitably altered salt concentration, but it is sometimes difficult now to induce pleomorphism unless a stock culture several weeks old is used as the inoculum.

The pleomorphism comprises aberrant forms similar to many of those which are regarded by certain observers as evidence of stages in a life cycle; but, in the case of the organism described, these forms can be induced by the simple expedient of altering the salt concentration of the medium on which it is grown. The occurrence of such forms is thus, of itself, no proof of a life cycle.

An investigation into an outbreak of Salmonella Newport infections in Canada was initiated in July 2020. Cases were identified across several provinces through whole-genome sequencing (WGS). Exposure data were gathered through case interviews. Traceback investigations were conducted using receipts, invoices, import documentation, and menus. A total of 515 cases were identified in seven provinces, related by 0–6 whole-genome multi-locus sequence typing (wgMLST) allele differences. The median age of cases was 40 (range 1–100), 54% were female, 19% were hospitalized, and three deaths were reported. Forty-eight location-specific case sub-clusters were identified in restaurants, grocery stores, and congregate living facilities. Of the 414 cases with exposure information available, 71% (295) had reported eating onions the week prior to becoming ill, and 80% of those cases who reported eating onions, reported red onion specifically. The traceback investigation identified red onions from Grower A in California, USA, as the likely source of the outbreak, and the first of many food recall warnings was issued on 30 July 2020. Salmonella was not detected in any tested food or environmental samples. This paper summarizes the collaborative efforts undertaken to investigate and control the largest Salmonella outbreak in Canada in over 20 years.

Test baiting has shown that rats underground are distributed in a series of discrete colonies, each one in close association with a group of men. Interplay between colonies is rare in large mines although evident in small ones. In the absence of stables the rats must depend almost entirely on miners’ food scraps.

These observations were made during work carried out under a research grant from Safety in Mines Research Establishment, Ministry of Power, and I am indebted to the Ministry for permission to publish the results. I should like also to express my gratitude to Dr E. T. B. Francis who supervised the work, Mr. C. S. W. Grice of the Ministry of Power and Miss B. B. Jones of the Ministry of Agriculture, Fisheries and Food for their help in various aspects of the work.

The early identification and prediction of hand-foot-and-mouth disease (HFMD) play an important role in the disease prevention and control. However, suitable models are different in regions due to the differences in geography, social economy factors. We collected data associated with daily reported HFMD cases and weather factors of Zibo city in 2010~2019 and used the generalised additive model (GAM) to evaluate the effects of weather factors on HFMD cases. Then, GAM, support vectors regression (SVR) and random forest regression (RFR) models are used to compare predictive results. The annual average incidence was 129.72/100 000 from 2010 to 2019. Its distribution showed a unimodal trend, with incidence increasing from March, peaking from May to September. Our study revealed the nonlinear relationship between temperature, rainfall and relative humidity and HFMD cases and based on the predictive result, the performances of three models constructed ranked in descending order are: SVR > GAM> RFR, and SVR has the smallest prediction errors. These findings provide quantitative evidence for the prediction of HFMD for special high-risk regions and can help public health agencies implement prevention and control measures in advance.

In Sudan, data on varicella infections are lacking and the vaccine is currently not in use. The aim of this study was to investigate previous exposure to varicella zoster virus (VZV) among children and adults from the general population and among health-care workers (HCWs) in Khartoum. Dried blood spot samples collected between 2015 and 2016 from 294 children aged 1‒15 years, 153 adult volunteers and 241 HCWs were investigated for the presence of VZV IgG antibodies using ELISA. The overall seroprevalence of VZV IgG antibodies among the investigated cohorts was 50.4%, ranging between 14.3% in children and 79.3% in HCWs. Seropositivity increased with age among children and HCWs (P ⩽ 0.05). A relatively low seropositivity (64.7%) was observed among young adults and HCWs, suggesting that a high proportion of Sudanese adults remain susceptible. In hospital settings, this result implies a risk of nosocomial infection involving both HCWs and vulnerable patients. The results of this first VZV study in Sudan suggest active virus circulation in different age groups. Especially HCWs at the start of their career might benefit from vaccination, not only to save themselves from herpes zoster and its sequelae, but also to indirectly protect vulnerable patients.

A simultaneous investigation into certain epidemiological aspects of scarlet fever was carried out over a 2-year period at Oxford, Cambridge and Cardiff. The results obtained at the three centres are compared and contrasted.

Nose and throat swabs were taken from 648 patients on admission to hospital; group A haemolytic streptococci were demonstrated in the swabs of 75·3 %. Eight days after admission 81·9 % had given positive swabs.

Serological typing showed that 56·9 % of strains were types 1–4. The only other common types were types 11 and 8/25.

The average length of stay in hospital was estimated for all cases, divided into groups according to whether or not they had suffered from complications or been cross-infected. The average for the whole series was 30·6 days; this was increased to 33·4 days for all complicated cases and to 37·6 days for all those cross-infected. It was longest (42·3 days) when there were both complications and cross-infections.

The incidence of cross-infection with fresh serological types of haemolytic streptococci was noted both in hospital and for the first 3 weeks after discharge. In the whole series 20·1 % of cases were cross-infected in hospital. The cross-infection rate was highest at Cardiff (27·9 %) and lowest at Oxford (13·5 %). Of the 123 cross-infected cases, complications occurred in 23·6%.

A total of ninety-eight patients (16·4 %) suffered from complications; in twenty-three of these (23·4%) complications were attributed to cross-infecting strains.

Nose and throat swabs were taken from all patients shortly before discharge; 60·3% were still carrying haemolytic streptococci.

Data were obtained regarding the rate at which cases became free of haemolytic streptococci. By the 10th week of the disease only 3·2 % of those who had not been cross-infected were carrying streptococci. Cross-infected patients were slower in becoming negative; at the 10th week 25·8% were still carriers.

There were fourteen return cases (return case rate 2·1%) following the return home of eleven primary cases (infecting case rate 1·7 %).

Swabbing of home contacts at the time of the patient's admission to hospital showed that one or more contacts of 25·5% of cases carried in their naso-pharynx the same type of haemolytic streptococci as that infecting the patient; 12·8% of the contacts swabbed were positive. During the first 3 weeks after discharge 24·6 % of contacts, that is one or more contacts of 55·5% of cases, carried a type that had been harboured by the patient while in hospital.

It was noted that in a particular area the common types that gave rise to scarlet fever also commonly caused other streptococcal infections of the upper respiratory tract. Type 12, however, though frequently found in other streptococcal infections and in healthy carriers, appeared only rarely to cause scarlet fever.

It is suggested that the low incidence of complications, less intimate relationship between complications and cross-infections and low return case rate found in this investigation, as compared to earlier observations made in England, are associated with lowered virulence and invasive powers of the strains of Str. pyogenes responsible for the much milder scarlet fever now prevalent.

The bacteriological findings confirm the wisdom of modern fever hospital practice of early discharge from hospital. It is suggested that discharge within 3 weeks should be the universally adopted rule.

The meaning of the footnote on p. 162 is somewhat ambiguous and the statement comprised in it is not true for all values of n, the number of differences in N.F.T. of which the significance of the mean is tested.

The statement that, by the use of a certain approximate distribution, significance of an observation is underestimated means that the estimated value of P in the neighbourhood of the significance level is greater than the true value.

On the basis of experience in using D.D.T. as an insecticide in both liquid and powder forms, suggestions are made for improved spray and dust guns.

My thanks are to S./Sgt. Toop, workshop foreman, and Pte Carter, tinsmith, of my old hygiene section, for the months of experiment, trial and error involved in producing these apparently simple innovations. Also to Brigadier H. B. F. Dixon, D.D.M.S. West Africa Command, for permission to forward this article for publication.

Pp. 474–485. Messrs W. Martindale inform us that the Lactic Acid Pessaries reported upon by Dr John R. Baker in the Journal of Hygiene, Vol. 34, pp. 474–485, are not recommended by them as a contraceptive. They are made to the order of a clinic. (Editor.)

P. 528, line 26, for “glucose media, and did not affect saccharose and maltose media” read “glucose and maltose media, and did not affect saccharose media”

It has been estimated that 75% of typhoid epidemics are water-borne, and it is not surprising, therefore, that many attempts have been made to prove the presence of the specific bacillus in the suspected waters, although the bacteriological examination for this purpose has always been recognised as most difficult and uncertain.

Strains of Corynebacterium diphtheriae isolated from a small outbreak in the restricted environment of a Mental Hospital were examined. All belonged to one serotype, but there was marked variation in diphthericin type, in sensitivity to bacteriophages and in the minor antigens possessed. One strain was non-virulent and laboratory-produced variants of this non-virulent strain showed changes in some of the characteristics used in the identification and typing of the organism, such as diphthericin type, sensitivity to bacteriophages and diphthericins, virulence, starch fermentation and, to a lesser extent, in antigenic structure. The epidemiological and experimental findings are consistent with the hypothesis that the strains isolated, both in the hospital and in the laboratory, were derivatives of a single parent and the mechanism of some of the variations could be related to changes in some structural component such as the cell membrane or the cell wall.

A metabolic inhibition test based upon phosphatase production is described. This is of value for those Mycoplasma species which produce phosphatase but which cannot be examined by the previously published metabolic inhibition techniques.

Numerouspapers have been published on the effect of heat on diphtheria antitoxin, but there appears to be no record of a series of observations carried out at a temperature nearly that of the human body. The object of this note is to fill in this slight gap in our knowledge.