The redispersal factor for bacteria-carrying particles from a contaminated floor was determined after mopping, blowing and walking activity. Walking gave the highest redispersal factor, 3·5×10−3 m−1, which was three times higher than for blowing and 17 times higher than for mopping. The mean die-away rate for the bacteria-carrying particles used was 1·9/h without ventilation and 14·3/h with ventilation. It was calculated that in the operating rooms less than 15% of the bacteria found in the air were redispersed floor bacteria.

Clean clothes in the staff dressing rooms were heavily contaminated with bacteria, mainly Bacillus sp., but Staphylococcus aureus were found on 14% and Clostridium sp. on 10% of the garments examined. A comparison of the occurrence of Staph. aureus on shirts worn by staff in wards and operating departments showed ward shirts to be contaminated more heavily and with more strains. Examination of sterile gowns worn by surgeons showed that 70% were contaminated with Staph. aureus after operation. Of the strains isolated 31% were identical with those carried by the surgeon or by the patient operated on, but for the remainder no source could be found.

Brains, spleens and livers of 2212 murids, 27 shrews and 7 dormice, trapped at 7 sites in Rhodesia, were tested in 277 pools for the presence of Rift Valley Fever virus. There were no isolations of Rift Valley Fever, but 69 isolations of an unidentified virus were obtained. Sixteen out of 867 sera had low-titre haemagglutination-inhibition activity against Rift Valley Fever antigen, but only one out of 1260 sera had neutralizing antibody. The evidence suggests that murids fail to encounter infection in nature and are unlikely to play a role in circulation and dissemination of Rift Valley Fever virus. Four out of seven widely distributed species of murid, Rhabdomys pumilio, Saccostomys campestris, Aethomys chrysophilus and Lemniscomys griselda, were shown to be capable of circulating amounts of virus likely to be infective for mosquitoes.

Bluetongue antibody of 19 different serological types was found in a group of sentinel cattle near Nairobi. A continuous challenge by these 19 strains occurred each year in this location. The sero-conversion rates were shown to vary from year to year and rainfall had no obvious effect upon the conversion rates.

The 19 different strains of virus were also shown to be active at five widely scattered sites in different parts of the country.

A group of 20 990 children in Uganda was examined for leprosy over a period of 8 years. There was no evidence that the incidence of leprosy varied according to a child's genetic relationship to a leprosy patient, once allowance had been made for the grade of physical contact.

Groups of 33 chickens were fed continuously on diets containing feed additives that are employed commercially for a variety of purposes, and were infected orally when 4 days old with a nalidixic acid-resistant mutant of Salmonella typhimurium. The amount of S. typhimurium organisms excreted in their faeces was estimated by culturing them at intervals and in a standard manner on brilliant green agar containing sodium nalidixate; when the chickens were killed their caecal contents were examined by the same technique.

Avoparcin and lincomycin, like nitrovin and tylosin (Smith & Tucker, 1975b), favoured colonization of the alimentary tract by the S. typhimurium organisms as shown by the fact that the chickens to which they were fed excreted these organisms in their faeces in higher concentration and for longer periods of time than did chickens fed on non-medicated diets. Amprolium, monensin, dimetridazole, arsenilic acid and nitro-hydroxyphenylarsonate had no obvious effect on the salmonella excretion pattern.

When only five chickens in each group were experimentally infected so that the effect of the feed additives on infections acquired by contact could be monitored, avoparcin, lincomycin, nitrovin and tylosin again favoured colonization of the alimentary tract with the S. typhimurium organisms and so did dimetridazole. Arsenilic acid, in contrast, hindered the development of infection. Amprolium, monensin and nitro-hydroxyphenylarsonate were without obvious effect.

Many of the chickens that were fed on diets that favoured S. typhimurium colonization, but not those fed on non-medicated diets, were still excreting S. typhimurium organisms in their faeces when they were killed at 56 days of age, the age at which broiler chickens kept under commercial conditions are usually slaughtered.

In a survey designed to determine the prevalence of Bacillus cereus in the faeces of healthy persons, the organism was found in low numbers in 100 (14%) of single faecal specimens from 711 adults in the general population. In addition, in an attempt at assessing the changes in the B. cereus distribution within the faecal flora of the individual, weekly faecal specimens were submitted over a seven-week period by 18 members of staff of two laboratories. The total isolation rate was again 14%, with 15 serotypes represented. In four individuals B. cereus was isolated in two consecutive weeks and in all cases the isolates were of different serotypes. Excretion was never recorded for more than two consecutive weeks. These findings probably reflect the intake of B. cereus in the individual's diet.

A model activated sludge treatment plant was used which was functionally very similar to a full-scale plant. It was inoculated with f2 coliphage and the titres of virus in the influent, the mixed liquor and the effluent were monitored regularly. The distribution of the virus in the solids and liquid fractions of the mixed liquor was in the ratio of 18:82 and 20–4 % of the influent virus was recovered in the effluent. After inoculation was stopped the titre of virus in the solids fraction of the mixed liquor remained high and unaltered for up to 70 h, whereas the value for effluent reverted to the low background titre originally present. These results are discussed in relation to those reported for poliovirus and it is concluded that f2 coliphage is not a suitable model for studies of the behaviour of human enteroviruses.

Volunteers were inoculated with vaccine made from the 30c mutant, A/Port Chalmers/73 or B/Hong/8/73. Preliminary experiments showed that the 30c strain was antigenically quite close to A/HK/8/68. Volunteers given 30c developed haemagglutination inhibiting antibodies against the ‘current’ 1973 serotypes (as well as to the vaccine virus) but the titres were less than those after the A/PC/73 vaccine. Volunteers were then challenged with a live attenuated virus, WRL 105, with A/Finland/4/74 antigens, by intranasal inoculation. The rates of infection were 43% after B/Hong Kong/8/73, 20% after 30c and 5% after A/PC/73. This indicated that the 30c gave some protection but the vaccine prepared from the current strain gave more.

Influenza activity was studied in the Rome population from 1956 to 1976 by analysis of mortality from respiratory causes and from all causes. During cold weather months, type A influenza virus was associated, as a rule, with epidemic excess deaths at two year intervals while type B virus was prevalent twice during epidemic excess mortality periods. Excess absenteeism from work and virus isolation data were also compared with epidemic excess mortality during four consecutive years. The evidence obtained indicated that influenza virus isolation alone does not represent a reliable index of epidemic influenza activity in this population. The proportion of deaths attributed to respiratory causes consistently increased in every epidemic, the most pronounced increases occurring during large epidemics. The break-down by age of deaths from respiratory causes in the course of two epidemic periods showed that the percentage distribution of deaths was essentially the same as in non-epidemic periods. This evidence indicates that the same factors influencing the age-related distribution of mortality from respiratory causes during non-epidemic periods, probably affect the fatal outcome of influenza during epidemics.

An investigation of the in vitro responsiveness of peripheral blood lymphocytes to tetanus toxoid was undertaken to determine the extent to which such reactivity might reflect in vivo reactions to tetanus toxoid immunization. It was found that lymphocyte transformation in the presence of tetanus toxoid, as measured by the uptake of tritiated thymidine, did not differ significantly for the group giving local or systemic reactions to tetanus toxoid and an immune control group. However, a striking inverse relation between lymphocyte reactivity to tetanus toxoid and age of the cell donors of both groups became clear. Such an age-related decline in the in vitro responsiveness of peripheral blood lymphocytes to a specific antigen has apparently not been reported previously in man.

The potential value of oral erythromycin for antitetanus prophylaxis in non-immune patients with open wounds was assessed. Serum obtained by venepuncture from healthy persons 2 h after an oral dose of an erythromycin preparation was used as a culture medium rendered anaerobic by addition of cooked meat. Strains of Clostridium tetani inoculated into these sera failed to multiply when the donor had taken 500 mg of erythromycin estolate before a meal; other erythromycin preparations and the estolate at a dosage of 250 mg were ineffective or inconsistent in their inhibition of the growth of Cl. tetani.

Human antitetanus globulin (ATG) was given to 12 patients, 9 with severe injuries and 3 with extensive burns, all of whom were judged, from their history, to be non-immune (or with expired immunity); all except one had received large intravenous infusions of blood and/or other fluids. Serum antitoxin assays by a mouse protection technique on days 0, 1–2, 3–5, 6–10 and 14 + showed no detectable antitoxin (< 0·01) unit/ml) in the initial (pre-ATG) sample from three patients with severe injuries and in one with extensive burns. All the patients in the severely injured group showed an early appearance or increase in tetanus antitoxin to protective titres. Two of the three severely burned patients showed, respectively, delayed appearance or an increase in antitoxin; the other burned patients showed a reduction from the initial pre-ATG titre, followed by a return to that titre after day 5.

Two epidemics of water-borne diarrhoeal disease involving a total of 1000 persons are reported. In both epidemics, none of the usual bacterial enteropathogens were recognized and Plesiomonas shigelloides was the only suspect aetiological agent isolated. The ecology of P. shigelloides was investigated in these outbreaks. It was recognized as an inhabitant of fresh surface water and its presence was closely related to warm weather.

A collaborative survey has shown that V. parahaemolyticus is widely distributed in British coastal waters, sediments and shellfish, especially in southern and western areas. The relatively small numbers in the environment do not present significant health hazards from marine products, provided that processing, storage and distribution are adequate. The presence of this organism in small numbers in British coastal waters or in shellfish should not in itself be regarded as cause for concern.

Twenty-four per cent of 2315 patients admitted to the intensive care unit of St Thomas's Hospital in the 4 year period from November 1969 became colonized or infected with Klebsiella species. Capsular typing of 986 klebsiella isolates from 551 patients showed that there were 695 patient-isolates, mostly derived from the respiratory tract. Capsular types 47 and 21 were the commonest types and together accounted for 19·9% of the patient-isolates. The 14 commonest types accounted for 47·3% of all patient-isolates and all these strains showed clustering, strongly suggesting a changing common source, cross infection, or both.

In these days of rapid transit from continent to continent, and the increasing mobility of people, agents of disease are no longer geographically restricted. Disease contracted half way across the world may become manifest in a country in which the pathogen is not normally found. Thus knowledge of the geographical distribution of pathogens becomes increasingly important when a diagnosis is being made. This is as true of ringworm fungi as of any other group of micro-organisms. In the last 12 years, in the Mycological Reference Laboratory, an increasing number of exotic dermatophytes have been seen, related in part at least to the great increase in the number of non-British residents.

Pen and field trials were conducted to assess the performance of the acute rodenticide pyriminil against the house mouse (Mus musculus L.). Four types of poison treatment were carried out using penned family groups of warfarin-resistant mice supplied with alternative plain foods. In each treatment pyriminil was included at 2% in a wholemeal flour/pinhead oatmeal/corn oil bait. Mortality was highest (46/54; 85·2%) when poison bait was offered for 4 days following 3 days of pre-baiting The same pre-baiting and poisoning technique was adopted in five field trials carried out against mice infesting farm building The efficacy of each poison treatment was estimated from the results of pre- and post-treatment census baitings; treatment success ranged between 53·7% and 96·7%, mean 80·5% It is concluded that pyriminil treatments are best carried out after a period of pre-baiting and that when pyriminil is used in this manner it is about as effective as zinc phosphide for the control of mice