In the period 1960–70 meat and poultry products caused over 70% of successfully investigated outbreaks of human salmonellosis. The number of human incidents of salmonellosis declined from 1960 to 1966, but then more than doubled between 1966 and 1971. This increase was mainly due to a threefold increase of incidents of salmonella serotypes other than Salmonella typhimurium. The serotypes which increased most and contributed significantly to this trend were S. enteritidis, S. panama, S. Stanley, S. virchow, S. Agona, S. 4,12:d:- and S. indiana.

Strong evidence exists that these serotypes have a path of infection from animal feedingstuffs to the pig and poultry animal reservoirs to pork and poultry foods to man. Cattle appear to be a less important source than pigs and poultry and this may be because the nature and content of their feed is different.

The importance of the control of the pig and poultry reservoirs of salmonella infections is stressed and a significant role of animal feedingstuffs in the maintenance of these reservoirs strongly suggested.

Ventilation of vessels varying widely in size was found to preserve the toxic effect of open-air factor(s). There was a correlation between the minimum rates of ventilation required and the ratios of the surface area of the vessels to their volumes. The data obtained allowed an estimate to be made of the diffusion coefficient of open-air factor(s) and gave an indication that the molecular weight range of the open air factor(s) was from 50 to 150.

Neuraminidase (N) can be extracted from virus particles of influenza B strains by treatment with trypsin, in a form which is free from the viral HA and has specific immunological activity. The N antigen of B/LEE/40 behaves differently from that of 1965–6 strains in gel diffusion and enzyme inhibition tests with animal antisera raised by infection or by artificial immunization with the homologous or heterologous strains. The frequency and titres of NI antibody detected in human sera by B/LEE antigen are different from those found with antigen from B/Eng/ 13/65. The latter antibody appears to contribute to the effect of serum HI antibody in protecting volunteers exposed to a deliberate intranasal challenge infection of the B/Eng/13/65 strain.

It has been shown that it is possible to investigate the colonization resistance in individual mice by determining the concentration of a certain contaminant (S.R.-E. coli) in the faeces during the first 4 days after contamination. Experimental contamination is contra-indicated in many cases such as in individuals with decreased resistance to infection. Particularly in this group, the value of the colonization resistance should be determined. It appeared to be possible to determine the colonization resistance in such individuals by quantitative biotyping of the Enterobacteriaceae species in the faeces on several consecutive days.

Of 60 TRIC agents isolated from Gambian children with trachoma, 25 were serotype 1 and the remainder type 2. There was a pronounced difference in the proportions of these types in the two villages studied. In the village with a predominance of type 2 strains, TRIC agents remained confined to 2 adjacent compounds over a 14 month observation period. All 19 type 1 strains examined were characterized by the appearance in yolk sac smears of compact aggregates of elementary bodies; such aggregates were seen in only 2 of 35 type 2 strains, and may reflect a chemical difference in the surface of the elementary bodies or in a substance elaborated during their replication.

In mice and in monkeys, ‘selective’ elimination of Enterobacteriaceae species from the digestive tract of animals with a sensitive flora was accomplished by oral treatment with nalidixic acid (1 mg./g. body weight in mice and 0·4 mg./g. body weight in monkeys). During treatment, the concentration of enterococci (and also of Candida albicans in the monkey) remained unaltered. This indicates that the fraction of the anaerobic microflora which is responsible for the colonization resistance of the digestive tract is not affected by the treatment. An important consequence seems to be, that elimination of yeast and fungi with fungistatic drugs can be started at the same time as elimination of Enterobacteriaceae is attempted.

The air of loose-boxes holding pigs affected with swine vesicular disease was sampled for virus. In the multistage impinger virus to a titre of 102·6 TCID50 was associated with particles greater than 6 μm., 101·6 with particles 3–6 μm. and 101·4 or less with particles less than 3 μm. In the noses of workers in contact with the pigs for periods not less than 5 min., virus to a titre of 102·4 TCID50 was found. Virus was recovered from the air for 2–3 days during the disease and maximum titre in pigs infected by injection or by contact occurred on the second to third day after generalization of the lesions. The amounts of virus were about 160-fold less than those recovered from pigs affected with foot-and-mouth disease, and the quantity and time of excretion suggest that the source of swine vesicular disease virus in the aerosol may be from the lesions and skin rather than from the respiratory tract.

An examination was made of the relations between antigen, antibody and fixation of complement with foot-and-mouth disease virus (FMDV). It was found that complement fixation in this system follows the same principles as models developed in other antigen/antibody systems. The assumption that there is a relation of direct proportionality between the amount of complement fixed and the amount of antiserum reacting with constant antigen was found to be incorrect. An alternative method was proposed for the quantitative differentiation of FMDV strains by comparing the titres of an antiserum when reacting with optimum amounts of homologous or heterologous antigens.

A total of 2525 strains of Escherichia coli were isolated from the faeces of 33 mothers, the faeces of their babies and the mucus extracted from the babies' mouths after delivery. Of these strains 1832 could be O-serotyped with 150 O antisera. E. coli were isolated from 28 babies and the same serotypes as were found in their mothers were found in 22 of them. E. coli was isolated from only 14 of the mucus specimens but in 12 of these at least one of the serotypes present was subsequently found in the babies' stools.

Although we have failed to produce either paroxysmal cough or vomiting in rhesus monkeys, cynomolgus monkeys and marmosets, we have found in marmosets several features of pertussis infection similar to those seen in children with whooping cough: catarrh, persistence of colonization of the naso-pharynx with Bordetella pertussis for 4–11 weeks, change of serotype during colonization and inability of type 1 organisms to establish themselves as the predominant serotype.

As in children, we have found that intramuscular vaccine of type 1,2,3 was more effective than type 1,2 in preventing persistent infection with the currently prevalent serotypes 1,2,3 and 1,3. A mixed vaccine (1,2,3 and 1,3) seemed to produce agglutinin 3 in the serum more consistently than a pure type 1,2,3 vaccine. The duration of colonization, after naso-pharyngeal challenge, was greatly reduced in animals with agglutinin 3.

Local immunity, resulting from previous infection, was even more effective than a good vaccine in preventing subsequent persistent colonization. Marmosets may be useful in studying the possible development of aerosol pertussis vaccine for human use.

Several foot-and-mouth disease virus strains were examined by complement-fixation tests in microplates and in tubes. It was established that the two systems are comparable, although greater reproducibility is obtained with tube tests. While microplate tests are a satisfactory method for the differentiation of strains, tube tests provide a more precise method for the identification of small antigenic differences.

For 6 months details of every patient who had his or her urine sent to a laboratory for bacteriological examination and the result of such examination were entered on a computer-card. A total of 15,606 cards were completed with information in code recording the sex and age of a patient, the origin of the request, the presence or absence in the urine of an excess of protein or cells, the culture result and the name of any significant organism isolated together with its sensitivity to various antimicrobial drugs. This information was interrelated in a computer, and in some cases the resulting numerical details were expressed as rates so as to eliminate the effect of uneven sex and age distribution. In this way the occurrence of urinary tract infection and the type of infecting organism in persons of either sex at various ages was examined according to whether the patient was in hospital or general practice. The sensitivity pattern of each type of significant organism isolated was established according to its source. The association between patients of either sex and various ages who had, or did not have, bacteriologically evident infections and the presence in their urine of an inflammatory exudate was investigated. Finally, the capacity of each type of infecting organism to produce such an exudate was estimated.

It was shown that hospital and general practice experience of urinary tract infections differed widely, with regard both to the age and sex distribution of those suffering from it, and to the causative organisms concerned and their sensitivities to antimicrobial drugs. It is suggested that these differences were so great that conclusions drawn from any study of this subject conducted in one of the two areas cannot be applied to the other, and that those derived from a mixture of the two will vary according to the relative sizes of each of the components.

The mean isolation rates of salmonellas from the mesenteric lymph nodes and faeces of healthy mink were 16·7% of 618 animals from three farms and 3·9% of 772 animals from four farms respectively. Salmonella senftenberg was the most commonly isolated serotype. S. typhimurium, S. dublin, S. livingstone, S. menston, S. enteritidis, S. bredeney and S. infantis were also seen.

The prevalence of salmonellosis in 316 dead mink from 12 farms was 0·6%.

The epidemiological aspects are discussed.

Three purified cell-wall glycoprotein antigens, a, b and c, sensitive to sodium periodate and resistant to pronase, were extracted from mycelium of Micropolyspora faeni with aqueous phenol or trichloracetic acid. Pronase-sensitive, sodium periodate-resistant protein antigens were extracted from mycelium with aqueous phenol. Immunoelectrophoresis was a critical method of assessing purity of preparation.

Antibodies to glycoprotein antigens only occurred in clinically defined cases of farmer's lung disease, whereas antibodies to protein antigens also occurred in symptomless farmers. Precipitins to a occurred in all cases of farmer's lung disease, and this antigen was isolated and purified.

Fractionation of pooled sera from cases of farmer's lung disease showed that precipitins were IgG globulins, whereas latex-agglutinating antibodies were IgG, IgA and especially IgM globulins. It is suggested that farmer's lung may involve a cytotoxic type II reaction, in which glycoproteins adsorbed to tissue cells react with IgG, IgA and IgM immunoglobulins in the presence of complement, causing cellular damage.

Sera from cynomolgus monkeys from Malaysia, from Indian rhesus monkeys, from various species of monkeys from Africa and from South America have been examined for neutralizing antibody to Tanapox and Yaba viruses. No antibody was found to either virus in the sera of rhesus monkeys or South American monkeys. A certain proportion of sera from cynomolgus monkeys and various species of African monkey showed antibody to one or other of the viruses, but few of the positive sera showed antibody to both. The results would seem to suggest that infection with the two viruses is endemic in African and Malaysian monkeys but does not occur or is very rare in Indian rhesus and New World monkeys.

The influence of obstructions and thermals on the air flow in unidirectional or laminar flow systems was studied with special reference to operating rooms. It was shown that thermals induced in the operating rooms would have little influence in the normal laminar-flow system. The importance however of obstructions such as operating lamps and personnel was shown.

Influenza-like illness, cold and sore throat was the diagnosis given in over 80% of 5177 acute respiratory illnesses in patients swabbed over a 10-year-period. A pathogenic organism was isolated twice as frequently from patients with a sore throat or an influenza-like illness as from those diagnosed as suffering from croup or laryngitis and bronchitis. A laboratory diagnosis was commoner in school children than in older or younger persons.

Most of the organisms isolated were found in association with all types of acute respiratory illness but, with increasing age of the patient, one particular agent or group of agents was more likely to be of aetiological significance.

Normal ferrets did not produce serum antibody following immunization with 200 i.u. of inactivated A/Hong Kong/68 influenza virus vaccine and were found to be susceptible to subsequent challenge infection with A/Hong Kong/68 virus. High titres of virus were recovered from nasal washings collected 3 days after infection, serum antibody was produced, increased nasal protein was detected and HI antibody was detected in nasal washings. Ferrets infected with influenza virus A/PR/8/34 7 weeks before immunization with inactivated A/HK/68 virus did, however, produce serum HI antibody to A/HK/68 virus. This antibody conferred partial immunity to challenge infection with A/HK/68 virus, as shown by decreased titres of virus in nasal washings and reduced levels of nasal protein. Previous infection of ferrets with influenza virus B/Ann Arbor/66 did not result in the production of serum antibody to A/HK/68 virus following immunization with A/HK/68 vaccine and the animals were completely susceptible to subsequent challenge infection with A/HK/68 virus. Differences in the amount of nasal protein and nasal antibody produced after A/HK/68 infection were also found in ferrets previously infected with either A/PR/8/34 or B/AA/66 virus, compared with normal ferrets.

The cytopathic effect of smallpox and camelpox viruses has been compared in cell cultures derived from human and monkey tissues. The two viruses could easily be distinguished in HeLa, GMK–AH1, BSC–1 and WISH cells, camelpox producing multinucleate giant cells and smallpox producing rounding up of individual cells. In other cells (LLC–MK2, HEK and 2RhK) the differences were not so marked, and in some (VERO, HEL, K and HuTh) no differences were seen.

During the period 1961–71 of 1785 viruses isolated from patients in the general population 503 (28%) were rhinoviruses, 465 (26%) influenza viruses, 248 (14%) enteroviruses, 234 (13%) herpes simplex virus, 132 (7%) parainfluenza viruses, 129 (7%) adenoviruses and 49 (3%) respiratory syncytial virus. Also isolated were 18 strains of mumps virus, 7 coronaviruses and 295 streptococci of groups A, C or G.

Fluctuations were observed in the frequency with which respiratory syncytial virus, parainfluenza virus type 2, and the adenoviruses were isolated over the 10-year period.

Influenza viruses types A and B, parainfluenza viruses types 1 and 2, respiratory syncytial virus, adenoviruses types 3, 4, 6, 7 and 21, and many enteroviruses were all associated with outbreaks.

Infections with influenza viruses A and B and parainfluenza viruses types 1 and 2 came during the winter, whereas those with parainfluenza virus type 3, enteroviruses, and rhinoviruses were more frequently seen in the summer and early autumn.