SARS-CoV-2 serological tests are used to assess the infection seroprevalence within a population. This study aims at assessing potential biases in estimating infection prevalence amongst healthcare workers (HCWs) when different diagnostic criteria are considered. A multi-site cross-sectional study was carried out in April–September 2020 amongst 1.367 Italian HCWs. SARS-CoV-2 prevalence was assessed using three diagnostic criteria: RT-PCR on nasopharyngeal swab, point-of-care fingerprick serological test (POCT) result and COVID-19 clinical pathognomonic presentation. A logistic regression model was used to estimate the probability of POCT-positive result in relation to the time since infection (RT-PCR positivity). Among 1.367 HCWs, 69.2% were working in COVID-19 units. Statistically significant differences in age, role and gender were observed between COVID-19/non-COVID-19 units. Prevalence of SARS-CoV-2 infection varied according to the criterion considered: 6.7% for POCT, 8.1% for RT-PCR, 10.0% for either POCT or RT-PCR, 9.6% for infection pathognomonic clinical presentation and 17.6% when at least one of the previous criteria was present. The probability of POCT-positive result decreased by 1.1% every 10 days from the infection. This study highlights potential biases in estimating SARS-CoV-2 point-prevalence data according to the criteria used. Although informative on infection susceptibility and herd immunity level, POCT serological tests are not the best predictors of previous COVID-19 infections for public health monitoring programmes.

Scrub typhus is a common bacterial infection in Asia caused by Orientia tsutsugamushi. This serological cohort study estimated the incidence of infection in a rural population in South India. Participants were enrolled through systematic sampling in 46 villages at baseline, and revisited the following year. Blood samples were tested for IgG antibodies using ELISA, followed by indirect immunofluorescence assays (IFA) in those positive for ELISA at both rounds. A case was defined as sero-conversion (ELISA), or at least a 4-fold titre increase (IFA), between the two time points. In addition to crude incidence rate estimates, we used piecewise linear rates across calendar months, with rates proportional to the monthly incidence of local hospital cases to address seasonality and unequal follow-up times. Of 402 participants, 61.7% were female. The mean age was 46.7 years, (range 13–88). 21 participants showed evidence for serological infection. The estimated incidence was 4.4 per 100 person-years (95% CI 2.8–6.7). The piecewise linear rates approach resulted in a similar estimate of 4.6 per 100 person years (95% CI 2.9–6.9). Considering previous estimates of symptomatic scrub typhus incidence in the same study population, only about 2–5% of infections may result in clinically relevant disease.

1. A given strain of Bact. aertrycke was sub-cultured daily, except on Sundays, in 5–7 c.c. of casein broth, pH 7·4–7·6, under different partial pressures of oxygen. Most experiments were continued till about ninety sub cultures had been made. Virulence determinations were made from time to time by intraperitoneal inoculation of twenty mice with about 100 living organisms, the control and the experimental cultures generally being tested simultaneously. The results showed that under anaerobic conditions there was no appreciable change in virulence. Under the usual aerobic conditions, and in partial pressures of oxygen varying from 1 to 21 per cent., the virulence declined, the extent and rapidity of the fall increasing with the pressure of oxygen supplied. In high partial pressures of oxygen, varying from 40 to 100 per cent., there was a slight increase in virulence, the increase being greatest in cultures incubated in pure oxygen.

2. Some of the literature dealing with incitants to microbic dissociation is discussed, particularly that dealing with variations in oxygen pressure.

3. In explanation of the experimental results obtained, a tentative hypothesis is put forward with reference to the dissociation of Bact. aertrycke. It is suggested that under aerobic conditions, and under low partial pressures of oxygen generally, substances are formed in the medium, as the result of growth, which favour dissociation, and lead to the appearance of weakly virulent or completely avirulent variants. Under anaerobic conditions these substances either are not formed at all, or appear in amounts too small to be of significance. In cultures incubated in high partial pressures of oxygen, these substances are formed, probably in large quantity, but owing to the high alkalinity of the medium and the abundant oxygen present, they undergo rapid destruction. This explanation is based on the fact that many protein degradation products, particularly those with a phenolic grouping, prove markedly unstable in an alkaline medium in the presence of free oxygen.

As an alternative hypothesis it is suggested that the maintenance of the organisms in the virulent state depends on the intracellular pH. Under anaerobic conditions it is supposed that the metabolism is such as to lead to no marked change in the H-ion concentration within the cell. In the presence of air and of low pressures of oxygen generally, owing to the breakdown of the protein in the medium and the production of ammonia, the intracellular reaction becomes more alkaline; whereas in high pressures of oxygen the increased amount of CO2 produced is sufficient to compensate for the production of ammonia, and the intracellular pH remains more or less at its original value. This hypothesis rests on the observation of Stephenson and Whetham (1924) that in high pressures of oxygen Bact. coli may produce considerably larger quantities of CO2 from lactic acid than under ordinary aerobic conditions; and on the demonstration by Jacobs (1920 b) that, owing to the ease with which CO2 is able to penetrate the living cell, the intracellular pH may differ markedly from that of the medium to which the cell is exposed.

4. It is of interest to note that Bact. aertrycke, when incubated under partial pressures of 40 to 75 per cent. of oxygen, rapidly passed into the nonmotile O form.

Although attempts to produce an active immunity against diphtheria were made as early as 1902, it is since the Schick test was described in 1913 that there has been available some clinically applicable measurement of individual immunity, naturally obtained or artificially produced; and it is probably true to say that large-scale active immunization has been practised in this country for only some 10 or 15 years.

Since disinfectants containing hypochlorites have been used for the sterilisation of dairy utensils, and it has been claimed that such disinfectants are more efficient than steam sterilisation, it seemed advisable to study the question in the interests of the Milk Industry. The efficiency of three proprietary disinfectants (A, B and C) has, therefore, been investigated.

Hecht (1923) states that the haemolytic activity of serum complement disappears on standing, but that the activity can be restored by the addition of heated fresh serum. It has also been shown (Gordon and Wormall, 1928; Gordon, 1930;. Gordon and Carter, 1932) that the bactericidal action of serum involves the activity of a complement similar to haemolytic complement and that inactivation of the latter by dilute ammonia and congo red causes, at the same time, inactivation of the bactericidal complement. The experiments now to be described show that the similarity of the two complements is exhibited once again in the effect of long standing on serum.

It is well established that plague, once it has gained a foothold in a place, tends to recur every year at the same season and that the plague season varies in different places. It has been demonstrated that in Bombay City the periods between the epidemics are bridged over by cases of acute plague amongst the rats accompanied by a few cases in man. Knowing, then, the factors which determine the rise and fall of the epizootic amongst the rats, once the infection is present, we have a fairly complete conception of the seasonal prevalence of human plague in a city such as Bombay. In the case, however, of a large province, such as the Punjab, with scattered villages, the question of the annual recrudescence in the several villages is not so simply answered. For, it will be remembered that in the two Punjab villages of Dhand and Kasel, which were under close observation by the Commission for a whole year, no acute plague was found amongst either man or rats in the long interval between the epidemics. While this is so, a certain number of rats were caught alive, which, although apparently in good health, harboured living and virulent plague bacilli in chronic abscesses (see above, p. 335).

Current methods of control recruitment for case-control studies can be slow (a particular issue for outbreak investigations), resource-intensive and subject to a range of biases. Commercial market panels are a potential source of rapidly recruited controls. Our study evaluated food exposure data from these panel controls, compared with an established reference dataset. Market panel data were collected from two companies using retrospective internet-based surveys; these were compared with reference data from the National Diet and Nutrition Survey (NDNS). We used logistic regression to calculate adjusted odds ratios to compare exposure to each of the 71 food items between the market panel and NDNS participants. We compared 2103 panel controls with 2696 reference participants. Adjusted for socio-demographic factors, exposure to 90% of foods was statistically different between both panels and the reference data. However, these differences were likely to be of limited practical importance for 89% of Panel A foods and 79% of Panel B foods. Market panel food exposures were comparable with reference data for common food exposures but more likely to be different for uncommon exposures. This approach should be considered for outbreak investigation, in conjunction with other considerations such as population at risk, timeliness of response and study resources.

A total of 375 separate sampling experiments were performed on groupings of 100 samples each from distinct binomial populations in order to obtain estimates of the frequency of rejection of the hypotheses of homogeneity against alternatives of a trend by means of the usual χ2 or binomial index of dispersion test. These artificial realizations are presented in Figs. 1–5, and compared graphically with corresponding non-central χ2 distributions.

The authors would like to acknowledge the technical assistance of the Research Computer Laboratory of this University in programming and supervising the computational phases of this investigation, which was partially supported by the State of Washington Initiative 171 Funds for Research in Biology and Medicine and the Boeing Employees' Good Neighbor Fund.

1. The respiration of bacteria normally present in thin slices of skin taken from pig's trotters has been measured in Cruickshank micro-respirometers.

2. These respirometers were originally designed to measure skin respiration in a medium including antibiotic to inhibit bacterial activity. The skin and medium was contained in a glass well. Using pig skin in a similar system without antibiotic, bacteria left the skin to grow independently in the medium. To overcome this difficulty polythene cups were made with an inner compartment for the tissue without medium and an outer compartment for water which provided a humid atmosphere.

3. Using polythene cups without medium the skin respiration was neglible, bacterial respiration was measured in situ and correlation between oxygen uptake and bacterial counts was obtained. This correlation was valid within experiments only.

4. Respiration of skin samples taken from adjacent areas of pig's trotter was similar, but there was large variation between samples from different trotters.

5. Respiration due to bacteria increased rapidly for 6–9 hr., followed by a slower increase. This may be due to a limited food supply or to a state of equilibrium.

Laboratory tests were carried out to assess the efficacy of gophacide as a rodenticide against the Norway rat (Rattus norvegicus) and the house mouse (Mus musculus). Results of feeding tests with wild animals suggest that the compound would be more useful against mice than rats, and that 0.3% would be a near optimal concentration for field trials for both species.

The hazards of using gophacide as a rodenticide are discussed.

Sera of 197 apparently well persons were tested for residual haemagglutination-inhibiting antibodies against live Hong Kong/68, A/FM/47 and A/PR/34 strains. Sera of 62 well persons, regularly exposed to contacts with swine, were tested against an inactivated A/New Jersey/76 antigen.

Those born some time before and during a certain influenza era showed a significantly greater proportion of homologous residual titres against the subtype prevailing in that influenza era, than those born after the termination of the same era.

In each of the seven age groups tested both the percentage of positives and the geometric mean titres were usually highest against the Hong Kong strain (representing the most recent era); the next highest were those against the FM1 strain and the lowest were those against the PR8 strain (representing the most distant of these three influenza eras).

The serological involvement of donors exposed to regular contacts with swine was relatively stronger against the New Jersey antigen than the response of other serum donors shown against the other three, more recent, prototypes of influenza virus A. The oldest age groups showed significantly lower antibody response against the PR8, FM1 and Hong Kong strains (but not against the New Jersey antigen) than the next one or two of the younger age groups.

Strains of Staphylococcus aureus were isolated at a single sampling from cows in a dairy herd. When typed by phage most showed a complex pattern of lysis with group III and IV phages. Cross-spotting of strains showed great lytic activity and ten phages were isolated. The parent strains were lysogenized with these phages and the effect on the phage typing pattern of 202 daughter strains from 25 parent cultures was studied. Phage action was often blocked completely, with up to four being blocked on the one strain. Those most frequently blocked were phage 101, 117, 307 and 42D.

The change by which a strain of B. dysenteriae Flexner becomes resistant to sulphonamides is similar in character to the change in B. coli mutabile from white (non-lactose-fermenting) to red (lactosefermenting).

The highest proportion of variants are found in papillae, while no variants are found in the growing margin of colonies.

Reversion does not take place during growth on sulphonamide-free media.

The variation is a direct and heritable response to a chemical stimulus and in adaptation to this part of the environment.

The variation described by Reiner Müller of B. typhosus on rhamnose and of certain coliform bacteria on arabinose may also be of the same nature.

Strains of B. dysenteriae Flexner resistant to sulphanilamide or sulphaguanidine 1/10,000 are only partially resistant to sulphathiazole 1/100,000 and to sodium sulphapyridine 1/10,000.

Technique. The size of (uncrowded) colonies on a plate containing 1/10,000 sulphanilamide or sodium sulphacetamide is a useful criterion of resistance or non-resistance, but a resistant strain must be able to grow on 1/5000 Sa and will not grow on 1/5000 Ssac.

The best culture medium for these tests is Lab. Lemco bouillon with agar, but without peptone.

In concluding I wish to express my thanks for their help to Prof. H. R. Dean, Prof. C. H. Browning, Drs E. T. C. Spooner, A. MacDonald, J. E. McCartney and R. D. Stuart. The sulphonamides I received through the kindness of the British Pharmacopoeial Commission and of Messrs May and Baker.

In an uncompleted study in 1965 microscopic haematuria in the second or third week after acute pharyngitis was found four times more often in patients with either microbiological or clinical evidence of dual infection with both group A streptococci and a virus than in patients with evidence only of infection with group A streptococci.

Prospective studies of the role of viruses in the aetiology of transient haematuria and of acute post streptococcal glomerulonephritis are feasible in general practice and would be most productive if concentrated in children 5–9 years of age.

Vaccination is a significant preventive measure to contain the coronavirus disease-2019 (COVID-19) pandemic. Vaccination rates can provide useful information on the potential spread of infection in a given population. In this study, vaccination rates and attitudes towards vaccination in cultural sectors, specifically the music sector, have been investigated. In total, 4341 persons in four different areas, including visitors to performances of classical music and musicals, as well as professional and amateur musicians, have participated in this survey. Results show rates of 86% recovered from the COVID-19 virus or vaccinated at least once, with 54.5% fully vaccinated. These vaccination rates were considerably higher compared to the general population. An attitude of hesitation towards vaccination found in 6.4% of those sampled was half that of the general population. These findings drawn from a large sample indicate that in the field of music a high vaccination rate is to be found, as well as a low rejection rate of vaccination on the part of the audience and performers. The results can be used to provide insights into the vaccination status to be found at cultural events and, importantly, to assist in consideration of whether cultural events should be permitted to continue under pandemic circumstances.

The outbreak of cattle plague in Egypt and the establishment of the Serum Institute at Abbassieh offered a suitable opportunity for investigating some points concerning the nature of the causal agent of the disease, and especially the important question whether the virus is, or is not, capable of traversing a filter candle. On this point the literature is strangely contradictory.

Salmonellosis is a foodborne disease of humans and animals caused by infection with Salmonella. The aim of this paper is to improve a deterministic model (DM) and an individual-based model (IBM) with reference to Salmonella propagation in flocks of laying hens taking into account variations in hens housed in the same cage and to compare both models. The spatio-temporal evolution, the basic reproduction number, R 0, and the speed of wave propagation were computed for both models. While in most cases the DM allows summary of all the features of the model in the formula for computation of R 0, slight differences between individuals or groups may be observed with the IBM that could not be expected from the DM, especially when initial environmental contamination is very low and some cages may get rid of bacteria. Both models suggest that the cage size plays a role on the risk and speed of propagation of the bacteria, which should be considered when designing new breeding systems.