The effect of the ionization of the air on the decay of bacterial aerosols was studied in a Burns and Plastic Surgery Unit. Ions were generated by free corona needles. The air content of bacteria measured by settle plates was found to be smaller during the ionization period than during the controls period. The number of individual phage typed Staph. aureus strains was especially found to be lower during ionization. The opposite potential increased the disappearance of bacteria from the air. The size of skin particles carrying bacteria is not optimum, but the results obtained show that the ionization may have applications in controlling airborne infection.

Immunization procedures with live attenuated and inactivated vaccines were carried out on a group of young recruits at the beginning of an outbreak of infection due to an A/Victoria/3/75-related virus strain, which occurred in February 1977 in a military camp. A retrospective investigation on protection from clinical influenza was then performed in order to investigate whether immunization with live virus vaccines, administered at the beginning of an epidemic, could provide early protection from the disease. In the course of the two weeks following vaccination, laboratory-confirmed clinical influenza cases occurred in 4 subjects among the 110 volunteers of the control group which received placebo, and in 8, 7 and 4 subjects respectively of the 3 groups of about 125 individuals, each of which received one of the following vaccine preparations: (a), live attenuated A/Victoria/3/75 influenza virus oral vaccine, grown on chick embryo kidney culture; (b), live attenuated nasal vaccine, a recombinant of A/Puerto Rico/8/34 with A/Victoria/3/75 virus; and (c), inactivated A/Victoria/3/75 virus intramuscular vaccine. These data do not support the hypothesis that, during an epidemic of infection, early protection from clinical influenza can be achieved through immunization with live attenuated or inactivated influenza virus vaccines, in spite of the high immunizing capability of the vaccine preparations.

By means of the spore fluorescent antibody technique, 31 strains of Clostridium botulinum types A (18 strains), B (10 strains) and F (3 strains) were found to belong to the same homogeneous group irrespective of their toxigenic types. Some strains of this species also cross-reacted with certain strains of Clostridium sporogenes types I, II and III and Clostridium histolyticum type II. By spore antigenic analysis it was found that Clostridium parabotulinum contained two components designated L and M, the former describing species specificity; the latter was the cross-reacting component shared by some strains of Clostridium sporogenes and Clostridium histolyticum. Following this, a scheme showing the distribution of spore antigenic components among various species of Clostridium was given.

We report an investigation into faecal carriage of Klebsiella aerogenes and the distribution of this organism in the environment of three wards. In all three wards faecal carriage rates were high (60–70%). The faecal carriage rate increased with antibiotic administration and with length of in-patient stay. K. aerogenes was widely distributed in the ward environment and was found on the hands of nursing staff. Clusters of isolations of K. aerogenes of the same serotype were demonstrated indicating either patient-to-patient transfer or a common source of infection. The results indicate that even under conditions in which there are no outbreaks of K. aerogenes infection, there is a large reservoir of this organism both in the bowel of patients and in the ward environment.

The antigenic varieties of influenza A virus isolated from 1968 to 1976 in a surveillance of a small, rather remote population were similar to those from England and Wales as a whole, despite frequent antigenic changes during the period. Household studies in the first two H3N2 influenza A epidemics found low attack rates within households, a high proportion (70%) of affected households with only one case of influenza, similar distributions of affected households in the two epidemics by the number of cases of influenza and similar distributions of the influenza cases by the day of their onset in the household outbreak. No serial interval could be demonstrated by cumulating household outbreaks. More than one minor variant was causing influenza contemporaneously in the same villages in several seasons, and different variants were on one occasion found on successive days in bedfellows. The regular occurrence of epidemics in winter was often accompanied by the disappearance of the epidemic variants and their replacement, after a virus-free interval, by new variants.

These epidemiological findings seem best interpreted on the following tentative hypothesis. Influenza A sufferers do not transmit the virus during their illness; instead it rapidly becomes latent in their tissues so that they become symptomless carrier-hosts and develop specific immunity. Next season an extraneous seasonally mediated stimulus reactivates the latent virus residues so that the carrier-host becomes briefly infectious, though symptomless. Antigenic drift occurs because particles reconstituted to be identical with the progenitor virus cannot escape the specific immunity it has provoked in the carrier host. He can shed only mutants also determined by the progenitor virus. From the assortment of mutants shed by the carrier-host, his non-immune companions select that (those) which is best fitted to survive, and it rapidly causes influenzal illness. Epidemics consist largely or entirely of such persons sick with influenza caused by reactivated virus caught from symptomless carrier-hosts.

This study describes aspects of measles in non-human primates. Monkeys infected before importation are shown to produce non-immune offspring in captivity in England. The high antibody titres found in most recently imported monkeys decline slowly during captivity in England. While measles is often fatal to monkeys, we have described an outbreak in which a number of symptomless infections occurred. Histological examination of fatal cases produced evidence of infection in the wall of the urinary bladder in one monkey. The close similarity between measles in humans and monkeys has been confirmed. It is considered that the study of infection among the latter may have significance for the former.

A study was made of the extent to which frozen broilers, contaminated with indicator organisms, can cause cross-contamination in the kitchen.

In 60 kitchens a number of relevant objects were sampled during the preparation of contaminated frozen broilers. The results show that cross-contamination occurred in a high proportion of the kitchens examined. In many instances the indicator organism was still present on various objects even after rinsing, ‘clearing’ or washing up. In view of the possible risk of a cross-contamination with Salmonella spp. the importance of instructing food preparers is emphasized.

No salmonellas could be found in the sinks of the 60 kitchens examined.

A study of Zika virus infections was carried out in four communities in Oyo State, Nigeria. Virus isolation studies between 1971 and 1975 yielded two virus isolations from human cases of mild febrile illness. Haemagglutination-inhibition tests revealed a high prevalence of antibodies to Zika and three other flaviviruses used. The percentages of positive sera were as follows: Zika (31%), Yellow fever (50%), West Nile (46%), and Wesselsbron (59%). Neutralization tests showed that 40% of Nigerians had Zika virus neutralizing antibody. Fifty per cent of Zika virus immune persons had neutralizing antibody to Zika alone or to Zika and one other flavivirus. A total of 121 sera had antibody to Zika virus; of these 48 (40%) also showed antibody to two other flaviviruses, and 12 (10%) had antibodies to three or more other viruses. The percentage of neutralizing antibodies to other flaviviruses in Zika virus immune sera was 81% to Dengue type 1, 58% to Yellow fever, 7% to Wesselsbron, 6% to West Nile and 3% to Uganda S.

The seroepidemiology of rubella infection in Hong Kong Chinese was examined by haemagglutination inhibition of normal sera and a comparison made where feasible with Caucasians living in Hong Kong. Taking reciprocal titre of 20 as a baseline, the incidence of maternally acquired antibody was 84% for Chinese and 90% for Caucasians. In babies up to 2 months this incidence was maintained in Caucasians but declined to 54% in Chinese. High titre antibody was more frequently detected in Caucasians generally, including women of child-bearing age. The detection of rubella-specific IgM in the Caucasian babies was suggestive of recent maternal infection. However, fewer Caucasian (20%) than Chinese (36%) women of child-bearing age (15–40 years) appeared unprotected against rubella. When all age groups were considered, 88% of Caucasians and 53% of Chinese were seropositive. The occurrence of a rubella outbreak during the study did not give rise to a significant increase in the incidence of seropositivity in Chinese 19–25 years, the only age group able to be evaluated in this manner. The ethnic differences in seroepidemiology are considered in the light of known HLA-1 and HLA-8 antigen distributions in Caucasian and Mongoloid people and the apparently low incidence of congenitally acquired rubella in Chinese.

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.

All of 86 foods routinely examined for potentially pathogenic enteric bacteria were found to harbour one or more coliform species. None of the strains isolated produced heat-labile enterotoxin (LT) or showed invasive properties. The suckling mouse test indicated that one strain of Escherichia coli produced heat-stable enterotoxin (ST). Twelve incidents of suspected food poisoning were also investigated. In two of them the foods examined contained LT-producing strains of E. coli and in two there were LT-producing strains of Klebsiella pneumoniae. The counts of viable enterotoxigenic micro-organisms in these foods were 3000–30 000 E. coli/g and 50 000 to 1 million K. pneumoniae/g. The dominant symptom in all the incidents was watery diarrhoea. These seem to be the first reported cases of foodborne enterotoxigenic enteric bacteria in Europe. Though enterotoxigenic E. coli and related gram-negative enterotoxin-producing species are rare in correctly handled food in Sweden, these micro-organisms should be searched for when outbreaks of food poisoning are investigated.

Attempts were made to correlate virus excretion, joint symptoms and antibody response with human leukocyte antigens (HLA) in seronegative adult women given attenuated rubella vaccine. No association was shown between HLA antigens of the A and B loci and excretion of either high or low titres of RA27/3 vaccine among 26 volunteers. However, virus excretion was influenced by such factors as the time of day at which specimens were collected and the method of virus isolation. Our study therefore failed to confirm the hypothesis that certain persons are good ‘spreaders’ of rubella virus and that this capacity is associated with HLA-A1 and B8.

The study of joint symptoms following vaccination with Cendehill, HPV77. DE-5, RA27/3 or To-336 vaccines showed no association between such symptoms and HLA antigens. However, joint symptoms occurred within 7 days of the onset of menstruation in 33 of 47 (70%) vaccinees (P < 0.01) and it is therefore suggested that hormonal factors must play a role. No association between HLA antigens and haemagglutination inhibition (HAI) antibody titres, 8 weeks after vaccination with RA27/3, was found amongst 34 volunteers.

Immunofluorescence (IF) and radioimmunoassay (RIA) have been compared as methods for detecting IgM antibody in 124 infants with confirmed or suspected congenital rubella. IF was used to test sucrose density gradient fractions and RIA to test fractions and whole serum.

When fractions were tested IF and RIA were equally specific and distinguished clearly between IgM and IgG, but RIA was the more sensitive method. The RIA titre in whole serum was always greater than in the peak IgM fraction and there was no evidence that testing the serum, rather than the fraction, could result in failure to detect IgM. With some sera RIA gave low titres which became negative after absorption with IgG-coated latex beads. The mechanism of this ‘false positive’ effect, which may have been due to IgM with anti-IgG activity, was not investigated, but if it can be removed by absorption it need not reduce the specificity of the test.

During the first 6 months of life IgM antibody was detected by RIA in 30 out of 32 unfractionated sera and by IF in fractions from 28 of these. After the age of 6 months IgM was found progressively less frequently and the greater sensitivity of RIA became a more obvious advantage: 17 out of 60 specimens were positive by RIA and 11 of these were negative by IF.

RIA testing of whole serum appears to be an economical, specific and sensitive method for detecting IgM antibody in congenital rubella, of particular value when the titre of antibody is low.

A prospective study of 2983 operations in general and orthopaedic surgery during 3 years performed in four operating theatres in a modern operating suite was carried out in order to evaluate the importance of airborne infection. Weekly nose-and-throat samples were taken from the surgical staff and pre-operative samples were taken from the nose, throat, skin and perineum of the patients. The air contamination was followed by using settle plates, which showed low mean counts of total bacteria of between 9 and 15 c.f.u./m2/min, with mean counts of Staph. aureus of between 0.03 and 0.06 c.f.u./m2/min. No correlation was found between the total number of bacteria and the incidence of post-operative infections or between the amount of Staph. aureus in the air and post-operative Staph. aureus infections. It was concluded that further increases in ventilation could, at best, only marginally affect the incidence of post-operative infection.

The post-operative wound-infection rate was 9.0%. In various types of surgery, the infection rates varied from 5.3% in clean operations to 47.6% in dirty surgery. About one third of the infections were classified as moderate or severe.

Adverse patient factors, such as immunodeficiency, steroid treatment, intensive care, etc., increased the rate to 15.0%; in ‘normal’ patients it was 3.8%.

Among the bacteria isolated, gram-negative bacilli (31% of wounds), often together with other bacteria, and Staph. aureus (28%) predominated, but in 25% no specimens were taken.

Of 76 post-operative Staph. aureus infections, 32 were caused by the patients' own strains, and of the remaining 44 infections, 22, or 8% of all infections, could be traced to strains present in the air and/or the respiratory tracts of staff during the operation.

The length of pre-operative hospital stay had no influence on the carrier rate of Staph. aureus in patients. The incidence of post-operative wound infection was significantly higher in patients carrying Staph. aureus and was even higher if these bacteria were found on the skin.

Patients with wound infections stayed, on an average, 15 days longer than patients without infections. In serious infections the increase in duration of stay was > 20 days. Although infections were commoner in older patients, the average additional hospital stay of infected patients did not increase with age. If the post-operative infections studied in a concurrent retrospective study are taken into account more than 12 000 bed-days were due to post-surgical wound infections in the period studied or, in other words, some 12 beds (corresponding to 5.5% of the total) were always occupied by infected patients.

A review of 50 hospital-based outbreaks of food poisoning which were reported in Scotland during 1973–7, is described. At least 1530 persons consuming hospital-prepared food were involved. Thirty-one episodes were associated with Clostridium perfringens (C. welchii), 11 were due to food-borne salmonella infection, three to enterotoxigenic Staphylococcus aureus, and five incidents were of undetermined aetiology. This differs noticeably from the experience in England and Wales where salmonellas appear to predominate as the main cause of hospital outbreaks. Twenty-two incidents occurred in hospitals for psychiatric or mentally subnormal patients, and ten others were located in geriatric units. Only 33 hospitals were involved in the 50 outbreaks as nine hospitals experienced two or more episodes.

The role of the hospital in the occurrence of food poisoning may be over-emphasized in comparison with other catering establishments, as outbreaks are more readily recognized and laboratory facilities are usually available for investigation, but it is also believed that many episodes may not be reported. The peculiar problems of the hospital-catering service and particularly those of the older long-stay hospitals, are discussed in relation to preventive measures which would minimize the hazards of food poisoning.

Serological studies on cows recovered from natural cowpox indicated that Haemagglutinin-Inhibiting (HAI) antibody persisted for at least 27 weeks, and Virus Neutralizing (VN) antibody persisted for at least 98 weeks.

The effect of artificial air-ionization on air-borne transmission of Newcastle disease virus (NDV) infection in chickens was studied in an isolated system consisting of two side-by-side cages with solid walls and a wire-gauze roof. During a 3-week observation period more than 90% of the uninoculated indicator chickens, housed in one of the cages, contracted the virus shed to the air by the NDV-inoculated, diseased birds in the neighbouring cage. This air-borne transmission of NDV was completely prevented by increasing the ion concentration in the test room by a constant negative corona discharge above the wire-gauze roof. On the other hand, spreading of the infection within a group of chickens housed in a single cage was not affected by air ionization.

These and other results suggest that artificial air-ionization may protect animals from certain air-borne infections by interfering with microbial aerosol formation and/or by facilitating their decay.

Sixty soil samples were collected from the redeveloped site of the former Metropolitan (Caledonian) Cattle Market, Islington, London. Of these, 15 (25%) contained Clostridium botulinum and no less than four types (B, C, D and E) were demonstrated.

Early British soil surveys suggested that only 4–8% of samples contained Cl. botulinum (type A or B). Although there can be no absolute proof, it seems likely that the striking prevalence at the Market site was the result of faecal contamination by a small proportion of the many millions of farm animals brought there from elsewhere.

The distribution of Clostridium tetani was uneven, but of 18 soil samples taken from one area of the Market site, 16 (89%) were positive.

An outbreak of staphylococcal sepsis in a burns unit occurred between January 1976 and May 1978. Many patients and members of staff had boils, and a number of patients also developed septicaemia. Most of the boils in the early period of the trial and a large proportion of boils in patients during the later period yielded Staphylococcus aureus resistant to penicillin, tetracycline and erythromycin only (PTE), and were shown to be of phage type 95 in the early period while strains were phage typed. From blood cultures, most strains in the early period were of resistance pattern PTE and phage type 95, but in the later period other resistance patterns were predominant. Strains from burns were usually multiresistant (PTEKNML) and of the phage pattern 29/77, which had been endemic in the Unit, but during the early period of the outbreak there was an increased proportion of strains in burns with the resistance pattern PTE and of phage type 95.

Staphylococcal sepsis has for many years been very infrequent in the burns unit. This outbreak seems to have been initiated by a strain of phage type 95 and resistance pattern PTE, but during the course of the outbreak the endemic strain of type 29/77 and some other staphylococci seem to have developed enhanced ability to cause clinical infections, conceivably by transduction from the epidemic strain of phage type 95.

A solid-phase radioimmunoassay (RIA) for detecting rubella virus IgA serum antibodies was developed. Purified rubella virus grown in roller cultures of Vero cells was adsorbed onto polystyrene beads. The coated beads were then incubated with dilutions of serum, and rubella IgA antibodies which attached to the virus antigen on the solid-phase were subsequently detected with 125I-labelled anti-human-alpha antibodies. The specificity of the iodinated anti-human immunoglobulins was confirmed by RIA analysis of fractions obtained by chromatography of an early convalescent serum on an agarose column. A complete separation of IgM, IgA, and IgG was observed.

A total of 144 serial serum specimens from 31 adult patients with an acute rubella infection were tested for rubella IgA antibodies, and the results were compared with the RIA IgG and IgM titres reported earlier from the same specimens. The RIA IgA response was detected in each of the 31 patients and the IgA antibodies appeared almost simultaneously with the IgG and IgM antibodies. The maximum titres, which were lower than the IgG and IgM titres, were reached in about 1 week after the onset of rash. In 6 patients out of 31 the IgA antibody response was transient and persisted approximately two months, while in the remaining 25 patients the IgA antibodies persisted throughout the study period of more than 5 months. The results obtained indicate that the presence of rubella IgA antibodies in serum is not an indication for a recent rubella infection.