1. Evidence is given that in recently inoculated persons the Widal reaction, even when serial quantitative tests are done, has no practical value in the diagnosis of enteric fever. Conscription enlarges permanently the inoculated proportion of the whole population.

2. The diagnostic value of any particular titre depends not only on the relative frequencies with which this titre occurs in normal and infected individuals but also on the incidence of enteric fever in the population and on the fashionableness of the Widal test as a diagnostic aid.

3. It is emphasized that blood culture is a more reliable aid to diagnosis than the Widal test.

It is shown that provided the total number of individuals exposed to a constant environment which is inducing change within them be constant, and the number of units of change which must take place within any given individual in order to cause a given event be also constant, then the number of these events is a quantitative measure of the extent of the change in all of the individuals taken together.

From this it follows that the results of Madsen and Nyman and of Chick may legitimately be regarded as proving that the process which underlies disinfection obeys the time-relations and other characteristics of a mono-molecular chemical reaction.

1. A method is described for estimating the disinfecting power of chemical substances on small cylindrical blood-clots of standard dimensions (about 1·5 mm. in diameter) containing a measured number of bacteria (Staph. aureus). It is capable of giving guidance for the use of disinfectants under the described conditions.

2. No practicable disinfectant regularly sterilized heavily infected clots (400,000 cocci) in 5 min. at 17–20° C.

3. In 30 min. the following were the only substances that were uniformly successful with heavily infected clots: 2·5% iodine in aqueous KI solution; 50% Chloros, containing about 5% chlorine; 70% alcohol containing 0·1% acriflavine. (The first of the three was tested on a larger scale than the others, and its potency is therefore the more firmly established.)

4. Reduction of the number of cocci in the clot increased the range of effective disinfectant solutions. Thus with 4000 cocci per clot regular clot disinfection was achieved in 30 min. with the following additional solutions: ethyl alcohol 70 and 50%; Chloros 25%; phenol 2·5% and lysol 1·25%. A few tests indicated that Zephiran (and probably CTAB) at 1 or 2% concentration would also pass this less exacting test.

Bacteriological contamination of a specific-pathogen-free (SPF) animal production building was more extensive after one year of operation than at the time of commissioning. Throat and nose swabs taken from the staff yielded a number of undesirable organisms, in particular, on one occasion, a Group A streptococcus. It is recommended that a closer bacteriological scrutiny of the staff of SPF production buildings ought perhaps to be made in the light of these findings.

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.

When staphylococcal strains from hospital patients are plotted in a frequency curve according to the size of the growth-free zone in a disk test for sensitivity to penicillin-G, this curve is trimodal. This implies that, besides the sensitive, there are two populations of resistant staphylococci: the moderately and the highly resistant, In a hospital-wide survey of coagulase or mannite positive staphylococci isolated in North Carolina Memorial Hospital between October 1964 and October 1965 it was inferred that: (1) there was a statistically highly significant difference between the distributions of the moderately and the highly resistant strains over duration of hospital stay prior to the time of isolation; (2) the highly resistant strains were seldom introduced from outside; and (3) there was no significant association between use of penicillin-G by a patient harbouring a strain and the frequency with which such a strain was found to be highly resistant to this drug. The latter finding is in contrast to significant associations found when the penicillin resistance is moderate, or when the drug used is other than penicillin-G. It is concluded that a fall in the incidence of staphylococcal strains highly resistant to penicillin-G in patients who did not receive other antibiotics may well be a valid index of the efficacy of programmes to control hospital infection. If so, there is a practical merit in adopting the routine of distinguisning between two groups of penicillin-resistant staphylococci, which behave, epidemiologically, as two distinct bacterial populations.

The history of the study by modern methods of the epidemiology of plague may be said to date from the discovery of B. pestis by Yersin and Kitasato in 1894. The severe outbreaks which since then have yearly recurred, notably in Bombay and Hongkong, have offered a wide field for investigation. That the opportunities thus afforded have not been neglected is sufficiently shown in the statement that in Bombay alone no fewer than six scientific commissions devoted their attention to various aspects of the disease within a few years. In addition, epidemics have been investigated in many places throughout the world.

Vaccination coverage and seroprevalence of poliovirus antibodies were assessed in Argentinean children (aged 8–12 and 19–21 months) living in Cordoba City pre-/post-implementation of a DTwP-IPV-Hib vaccination programme, and compared to those of controls from neighbouring populations receiving a full oral poliovirus vaccine schedule. Vaccination coverage was higher in control areas pre-intervention; this increased post-intervention in Cordoba (>90%) but not in control areas. Poliovirus types 1 and 2 seroprotection rates were >97% in all groups pre-/post-intervention. Type 3 seroprotection rates were generally lower, but increased post-intervention in Cordoba becoming significantly higher than control rates. Anti-type 1 and 3 antibody titres increased twofold and sevenfold, respectively, post-intervention, whereas anti-type 2 antibody titres decreased ~40% in the 8–12 months group. All titres increased in the 19–21 months post-intervention group. The introduction of a three-dose primary DTwP-IPV-Hib schedule maintained protection against poliovirus types 1 and 2, and increased protection against type 3, while vaccine coverage in the study area increased.

1. The relation between lethal doses of diphtheria toxin and the times in which they kill guinea-pigs, or lethal times, is approximately such that the lethal dose multiplied by the corresponding lethal time gives a constant value—a hyperbolic relation.

2. Deductions with regard to lethal doses from deaths occurring on the first day or on any day after the sixth give such widely divergent results that, in our opinion, they are at present of negligible value.

3. Under the ordinary circumstances of standardisation of diphtheria toxin and antitoxin the relation given in conclusion No. 1 is as close an approximation as any alternative likely to prove of practical utility.

4. The graphic representation of L+ doses against lethal times gives a straight line relationship.

5. Five of the best investigated toxins confirmed Ehrlich's views in so far as that with toxicities diminishing by 50% their neutralising powers remained practically unimpaired.

6. The individual sensitivities of guinea-pigs to free diphtheria toxin render any general relation between lethal times and doses of little value when a small number, e.g. 5, of test animals is inoculated.

7. Even with a dose of toxin which would, in any ordinary series of tests, be regarded as an L+ dose, 5 out of 33 guinea-pigs survived the sixth day or 15%1, and the m.l.d. of a well-investigated toxin showed similar variations; consequently both the L+ and m.l.d. values of a toxin are not those amounts which kill with certainty in a fixed time, but those which will cause death in that time with the greatest probability.

8. After inoculation, guinea-pigs unless suffering from the consequent “shock,” continue to increase in weight throughout the first day, even with doses that may subsequently prove lethal, and with highly toxic doses the variation in weight during this time is of little significance.

9. The greater the amount of free toxin injected, the more rapid is the increment in weight followed by a decrement.

10. The weight of a test animal at the end of 24 hours after inoculation forms a better normal or origin with which to compare the subsequent time-weight relations than the initial weight before injection.

11. On the basis of Conclusion 10 the general connection is found that with increasing amounts of free toxin the position of the maximum loss of weight is gradually transferred from the second to the fifth day for guinea-pigs which survive over six days.

12. The time-weight ratios for almost certainly lethal doses give straight line connections, corresponding probably to starvation curves of the guinea-pig.

A quantitative method for testing serum diphtheria antitoxin levels was set up using a diphtheria antitoxin radioimmunoassay (RIA). The results of this RIA correlated well with the Schick test in 554 subjects and with intradermal neutralization tests in guinea-pigs in a small group of subjects. The RIA was suitable for use on blood collected by fingerprick on to a disc of standard chromatography paper. These discs could be stored at room temperature for at least 1 month. If storage for more than 6 months was required –20 °C was found to be better. Experience with this RIA in a total of 2349 subjects indicated that it is more accurate, rapid and less costly than Schick testing. The RIA should prove to be the preferred method for testing diphtheria immunity in population surveys.

The ongoing pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to an unprecedented global public health crisis. The objectives of this study were to analyse the dynamic trend in specific antibodies in the serum of patients infected with SARS-CoV-2 within 12 months after recovery and to make a preliminary assessment of the protective effect of vaccination. Eighty-seven patients with confirmed COVID-19 who were admitted to our hospital from January to February 2020 were followed after recovery. Three-millilitre blood samples were collected for specific antibody detection at four time points: 1, 6 and 12 months after recovery and 1 month after vaccination. The changes in specific immunoglobulin G (IgG) antibody and total antibody levels over 12 months were analysed. Moreover, an independent comparison of the neutralising antibody levels of patients after vaccination with those of healthy medical staff after vaccination was performed to compare the inhibition rates of the neutralising antibody to the virus. No statistically significant difference in the sex distribution between groups was observed (P > 0.05). Older patients had a greater risk of developing severe and critical COVID-19 (P < 0.05). The percentages of subjects positive for IgG antibodies at 1, 6 and 12 months after recovery were 88.5%, 75.9% and 50.6%, respectively. The rate of IgG antibody conversion from positive to negative was not uniform across time points: the change was slow in the first 6 months but increased significantly in the last 6 months (P < 0.05). The positive rate of critically ill patients in the first 6 months was 100.0%. The trend over time in total antibody levels was similar to that of IgG antibody levels. Over 12 months, the sample/cut off value of total antibodies continued to decrease, while that of different disease severities was significantly different (P < 0.05). After vaccine administration, the total antibody level exceeded the detection level in the first month, which was independent of disease severity (P > 0.05). Significant differences were observed in the inhibition rate of the neutralising antibody against the virus in the disease group and the control group (P < 0.05). IgG antibody produced by patients naturally infected with SARS-CoV-2 has a duration of no less than 1 year, and the change trend graph of total antibody levels was the same as that of IgG antibody levels. Under vaccine stimulation, the positive rate of IgG antibody was as high as 100%, and the total antibody concentration reached the highest level, which was independent of disease severity. Neutralising antibodies following vaccination in patients who recovered from COVID-19 had a higher inhibition rate against SARS-CoV-2 than those of vaccinated healthy controls, indicating that these COVID-19 patients had a lower risk of reinfection and were better protected.

The maintenance of a constant supply of healthy guinea-pigs is an important part of the work of laboratories which are engaged in the production of diphtheria and tetanus antitoxin. The subacute infective processes to which malnutrition predisposes enhance the effect of the test dose of toxin, with the result that irregular deaths among the animals under test render difficult the titration of the antitoxin. For this reason it is desirable that breeding stocks should be kept in suitable animal houses under the best hygienic conditions possible. This policy has been followed in the Serum Department of the Institute for many years; there have been comparatively few introductions of stock from outside sources, and within recent years special attention has been devoted to diet.

National disease surveillance systems are essential to a healthy pig industry but can be costly and logistically complex. In 2019, Lao People's Democratic Republic (Lao PDR) piloted an abattoir disease surveillance system to assess for the presence of high impact pig diseases (HIPDs) using serological methods. The Lao Department of Livestock and Fisheries (DLF) identified Classical Swine Fever (CSF), Porcine Respiratory and Reproductive Syndrome (PRRS) and Brucella suis as HIPDs of interest for sero-surveillance purposes. Porcine serum samples (n = 597) were collected from six Lao abattoirs in March to December of 2019. Serological enzyme-linked immunosorbent assay (ELISA) methods were chosen for their high-throughput and relatively low-costs. The true seroprevalence for CSF and PRRS seropositivity were 68.7%, 95% CI (64.8–72.3) and 39.5%, 95% CI (35.7–43.5), respectively. The results demonstrated no evidence of Brucella spp. seroconversion. Lao breed pigs were less likely to be CSF seropositive (P < 0.05), whilst pigs slaughtered at <1 year of age were less likely to be PRRS seropositive (P < 0.01). The testing methods could not differentiate between seropositivity gained from vaccine or natural infection, and investigators were unable to obtain the vaccine status of the slaughtered pigs from the abattoirs. These results demonstrate that adequate sample sizes are possible from abattoir sero-surveillance and lifetime health traceability is necessary to understand HIPDs in Lao PDR.

The diagnosis of bubonic plague in rat cadavers, the examination of which is a recognised method of prophylaxis for ships or other communities, which may have been in contact with endemic centres, is attended by especial difficulties, and, on the other hand, calls for especial speed and finality in technique.

A clinical trial was initiated in South Africa before the winter season of 1976. The study involved 253 volunteers divided into three groups of vaccinees and one control group.

Two groups of vaccinees were inoculated with either one or two doses at 2 weeks' interval (107·2 EID 50/dose) of the RIT 4025 live recombinant strain [A/Scotland/840/74 (H3N2) serotype] and one group received one injection of an inactivated vaccine [A/Port Chalmers/1/73 (H3N2), 360 i.u., A/Scotland/840/74 (H3N2), 300 i.u. and B/Hong Kong/8/73, 300 i.u./dose].

The serum antihaemagglutinin antibody responses against the heterologous A/Victoria/3/75 strain as measured by the single radial haemolysis test were satisfactory and not statistically different in all groups of vaccinees. On the other hand, the antineuraminidase antibody response was better in the group receiving the killed vaccine.

At the end of the influenza season, A/Victoria/3/75 infections were confirmed serologically.

Only 12% of the infections were symptomatic. The infection rate was significantly reduced in the live vaccine groups, whereas in the killed vaccine group the percentage of infection was lower but not significantly different from that in the placebo group.

Toxigenic diphtheria is rare in Australia with generally fewer than 10 cases reported annually; however, since 2020, there has been an increase in toxin gene-bearing isolates of Corynebacterium diphtheriae cases in North Queensland, with an approximately 300% escalation in cases in 2022. Genomic analysis on both toxin gene-bearing and non-toxin gene-bearing C. diphtheriae isolated from this region between 2017 and 2022 demonstrated that the surge in cases was largely due to one sequence type (ST), ST381, all of which carried the toxin gene. ST381 isolates collected between 2020 and 2022 were highly genetically related to each other, and less closely related to ST381 isolates collected prior to 2020. The most common ST in non-toxin gene-bearing isolates from North Queensland was ST39, an ST that has also been increasing in numbers since 2018. Phylogenetic analysis demonstrated that ST381 isolates were not closely related to any of the non-toxin gene-bearing isolates collected from this region, suggesting that the increase in toxigenic C. diphtheriae is likely due to the expansion of a toxin gene-bearing clone that has moved into the region rather than an already endemic non-toxigenic strain acquiring the toxin gene.

Among the properties of the red blood corpuscles, that have from time to time been investigated, the resistance of this type of cell to the destructive action of various lytic agents occupies a place of some importance. Very many substances have been studied from this point of view, and no useful purpose would be served by enumerating them here; but it should be noted in passing that, as regards the great majority of them, we have no evidence that they play any part in blood destruction as it occurs “in vivo” under either physiological or pathological conditions.