The second patient with Arizona gastroenteritis to be diagnosed in Britain had just returned from the United States, where his illness began.

Studies were made in a modified hospital ward containing 19 beds, 14 of them in the open ward, one in a window-ventilated side-room, two in rooms with partial-recirculation ventilators giving 7–10 air changes per hour, and two in self-contained isolation suites with plenum ventilation (20 air changes per hour), ultra-violet (UV) barriers at doorways and airlocks.

Preliminary tests with aerosols of tracer bacteria showed that few bacteria entered the plenum or recirculation-ventilated rooms. Bacteria released inside mechanically ventilated cubicles escaped into the corridor, but this transfer was reduced by the presence of an airlock. UV barriers at the entrance to the airlock and the cubicle reduced the transfer of bacteria from cubicle to corridor.

During a period of 4 years while the ward was in use for surgical and gynaecological patients, the incidence of post-operative sepsis and colonization of wounds by multiple-resistant Staphylococcus aureus was lower (though not significantly lower) in the plenum-ventilated rooms than in the open ward, the recirculator-ventilated cubicles and the window-ventilated cubicles. Nasal acquisition of multiple-resistant Staph. aureus was significantly less common in the plenum-ventilated than in the recirculator-ventilated cubicles and in the other areas. Mean counts of bacteria on settle-plates were significantly lower in the plenum-ventilated cubicles than in the other areas; mean settle-plate counts in the recirculator-ventilated cubicles were significantly lower than in the open ward and in the window-ventilated side-room; similar results were shown by slit-sampling of air. Mean settle-plate counts were significantly lower in all areas when the ward was occupied by female patients. Staph. aureus was rarely carried by air from plenum-ventilated or other cubicles to the open ward, or from the open ward to the cubicles; though staphylococci were transferred from one floor area to another, they did not appear to be redispersed into the air in sufficient numbers to infect the patients. Ultra-violet irradiation caused a significant reduction in the total and staphylococcal counts from the floors of airlocks, and a significant reduction of total counts in the air.

The use of plastic isolators and of an ‘air curtain’ isolator for protection of patients against infection was studied in a burns unit.

Preliminary bacteriological tests showed that very few airborne bacteria gained access to a plastic ventilated isolator; even when the filter and pre-filter were removed from the air inflow, settle-plate counts inside the isolator were much lower than those in the open ward, but the difference was smaller in tests made with an Anderson air sampler, which showed also that fewer large bacteria-carrying particles appeared inside the isolator than outside it. An open-topped isolator allowed virtually free access of bacteria from ambient air. The numbers of airborne bacteria inside an air curtain were appreciably lower than the counts of airborne bacteria in the open ward, but not as low as those in the plastic ventilated isolator.

Controlled trials of isolators were made on patients with fresh burns of 4–30 % of the body surface; the patients were given no topical chemoprophylaxis against Staphylococcus aureus or Gram-negative bacilli. Patients treated in plastic isolators showed a significantly lower incidence of infection with Pseudomonas aeruginosa than those treated in the open ward; this protective effect was shown by isolators with or without filters or with an open top. Ventilated isolators, which protected patients against personal contact and airborne infection, gave a limited protection against multi-resistant ‘hospital’ strains of Staph. aureus, but no such protection was given by an open-topped isolator, which protected only against personal contact infection, or by air curtains, which protected only against airborne infection; the air curtain gave no protection against Ps. aeruginosa, and there was no evidence of protection by any isolator against Proteus spp. and coliform bacilli.

Both the controlled trials and evidence from the bacteriology of air, hands, fomites and rectal and nasal swabs taken on admission and later, supported the view that Ps. aeruginosa is transferred mainly by personal contact, Staph. aureus probably by air as well as by contact and coliform bacilli mainly by self infection with faecal flora, many of which are first acquired from the hospital environment in food or on fomites.

The use of plastic isolators is cumbersome, and of limited value except in the control of infection with Ps. aeruginosa. For this reason and because of the effectiveness of topical chemoprophylaxis such isolators are unlikely to have more than an occasional use in the treatment of burns. Though air curtains greatly reduce airborne contamination, their use in a burns unit does not appear to protect patients against infection when the alternative (and, for Ps. aeruginosa, more important) routes of contamination by personal contact and fomites are left open.

No evidence of vaccine virus transmission was found in two studies where Wistar RA 27/3 rubella vaccine was administered intranasally. Vaccine was immunogenic in all of 23 vaccinated children in one study, while in the other only 5 of the 11 vaccinees developed antibody. The reduced seroconversion rate in the latter study appears to have been caused by one or a combination of factors, including the vaccination technique, the presence of infective nasal conditions in vaccinees and the titre of vaccine used.

A streptococcal antigen that is closely associated with the M-antigen, but is not type specific can be detected by means of a complement-fixation test in extracts of M-positive, but not of M-negative, variants of group A streptococci. Purification of acid extracts results in a concomitant increase in the purity both of the type-specific M-antigen and of the M-associated protein (MAP). Antibody to MAP is present in the sera of patients who have had streptococcal infection. The highest titres are found in patients with rheumatic fever.

Thirty-three of 72 heroin addicts attending a recognized clinic for drug addition had a history of jaundice, but in only five was the serum positive for hepatitis-associated antigen (HAA) when examined by immunodiffusion, immunoelectro-osmophoresis and complement fixation. Two of these were repeatedly positive over an 8–12 month follow-up period and liver biopsy showed chronic persistent hepatitis. A third later developed acute hepatitis. A study of the injection habits suggested that the present low incidence of HAA and the decrease in number of cases with jaundice was probably related to the provision of free disposable syringes by the clinic since it was opened in 1968.

Thirty-seven volunteers were inoculated intranasally with living attenuated influenza A 2 viruses. Rising titres of circulating antineuraminidase (AN) were detected in 14 of 17 infected volunteers. AN was also found in nasal secretions. Statistical analysis showed that there was a correlation between the titres of haemagglutination-inhibituig antibody (HI) and AN in nasal washings, and between AN in blood and washings. Resistance to infection could be predicted from antibody titres in 29 of 37 volunteers and blood AN alone predicted the outcome of 25 volunteers.

This study of 724 13-year-old schoolgirls in the County Borough of Reading showed that approximately 25% were susceptible to rubella. 96·1% of the 129 seronegative girls and significant numbers of girls with low rubella HAI antibody titres responded to subcutaneous vaccination with Wistar RA. 27/3 rubella vaccine. The incidence of most reactions after vaccination was similar in those who responded to vaccine and those who were initially immune but did not develop rising antibody titres, but rash, lymphadenopathy and headache occurred significantly more frequently in the susceptible group.

Influenza C virus antigen could be detected by immunofluorescence in chick amniotic epithelium 4 hr. after inoculation with undiluted amniotic fluid. Antigen could be detected in the nucleus of rhesus monkey kidney tissue cultures 10 hr. after infection. Only cytoplasmic fluorescence was observed 17–21 hr. after infection.

The pattern of replication was similar to that reported for group I myxoviruses, indicating that the virus is correctly classified as an influenza virus.

Mycoplasma gallisepticum antigens were prepared from organisms cultured in broth medium with glucose. The influence of period of growth, pH of the medium and duration of incubation at low pH (5·0) on the sensitivity of these antigens was determined in certain tests. The most sensitive antigen for the serum plate test was harvested after no more than 8 hr. incubation at pH 5·0. Sensitivity in serum plate, haemagglutination and gel diffusion tests was impaired if organisms were incubated at pH 5·0 for long periods. Antigens prepared from buffered broth medium were found to be at least as sensitive as those from unbuffered medium for the haemagglutination and gel precipitation tests, but considerably less so for the serum plate test.

An indoor system designed for the study of survival of airborne micro-organisms in closed conditions has been successfully modified to allow the effect of open air to be measured. It was found that the unidentified open-air factors which are toxic for many species of microbes and rapidly lost when enclosed in conventional laboratory apparatus could be retained in the system by continuous ventilation at an adequate rate. The rate required allowed examination of Escherichia coli in aerosols generated from small amounts of material because of the short periods of ventilation required for appreciable viable decay to occur.

The validity of the system was tested by comparing the survival of E. coli in true aerosols with its survival when the droplets were held on microthread. An investigation of the role of relative humidity in open-air toxicity was included.

Airborne Semliki Forest virus and T coliphages were inactivated at a considerably enhanced rate in open air compared with enclosed air. Open air exerts its maximum sterilizing activity on viruses contained in the smallest sized particles.

In the course of developing a living attenuated feline infectious enteritis (panleucopaenia) vaccine, it was found that respiratory disease-infected cats newly inoculated with this vaccine spread vaccine virus to respiratory disease-infected in-contact controls. These in-contact controls were able to infect other cats with which they were placed in contact so that after five natural transmissions in this way and two oral administrations and subsequent re-isolations, reversion to virulence became evident. It is clear that before general release of a new living feline infectious enteritis vaccine, there must be satisfactory evidence that con-current infection will not affect the safety of the modified antigen.

In cats infected with feline infectious enteritis there appears to be a short period, coinciding with the onset of leucopaenia, during which they are highly infectious. It seems possible that some infected animals may become immune carriers because virus has been recovered from the small intestine of two of four cats with significant antibody titres 22–24 days after exposure to infection.

The propensity of an attenuated strain of feline infectious enteritis (panleucopaenia) virus to spread from vaccinated cats affected with intercurrent feline respiratory disease to unvaccinated in-contact cats was eradicated by further passaging of the vaccine virus in tissue culture. No virus was recovered from, and no antibody was found in the sentinel cats in contact with seven vaccinated animals. Thus, a further 27 passages of the vaccine virus in tissue culture has eliminated the spread factor.

Sera were examined from 50 patients on the renal transplant unit, Cambridge, for antibody against cytomegalovirus by complement fixation and by immuno-fluorescence for IgG and IgM antibodies.

The incidence of antibody on admission was 84% with a possible further 8% so that nearly all had been infected at some time by CMV.

43 (86%) patients showed evidence of active infection after admission, 39 by serology and four only from the examination of post-mortem material.

Twenty-one patients produced IgM antibody and production was prolonged for years in patients that survived. Antibody production was related both to transplantation and admission to hospital.

The evidence indicated that primary CMV infections were rare, that IgM anti-body production was the result of active infection and that this could be attributed to reactivation without the need to invoke re-infection as the source although this type of patient is both susceptible and exposed to re-infection.

The aerosol survivals in air and nitrogen of radiation sensitive and resistant mutants of Escherichia coli B have been determined with logarithmic and resting phase bacteria. No consistent correlation was found between radiation sensitivity and aerosol sensitivity in the strains tested. Hence, the phenotypes Fil Her Exr, which determine sensitivity to radiation, do not influence aerosol survival, i.e. these known mechanisms which repair radiation-induced damage do not operate in aerosol stressed E. coli. In all cases the survival in air was less than that in nitrogen particularly so for E. coli Bs-1. The effect is explained in terms of a toxic action of oxygen. Comparison of survival of log and resting phase bacteria show that log phase cells are less aerosol stable than are resting phase cells. The ability to synthesize DNA in bacteria collected from the aerosol was less than in control unstressed bacteria, and this effect was independent of the presence of oxygen. Reduced ability to synthesize DNA could have been caused by reduced metabolic activity. It is shown that two different death mechanisms occur simultaneously in aerosols at low relative humidity. One mechanism is oxygen dependent and the other oxygen independent. The former was not through a decrease in metabolic activity, whereas the latter could be.

The survival of salmonellas on the finger-tips is considered with reference to the ease with which they can be transferred to food by handling.

Escherichia coli and several Salmonella serotypes were shown to survive on the finger-tips for various periods of time, for example, S. anatum could be recovered 3 hr. after artificially contaminating them with between 500 and 2000 organisms. S. anatum could also be recovered from the finger-tips after contaminating them with more than 6000 organisms followed by a 15 sec. hand-wash 10 min. later. Similarly, the survivors from minimal inocula of less than 100 S. anatum/finger-tip were, after 10 min., still capable of infecting samples of corned beef and ham. E. coli was isolated from the finger-tips of 13 of 110 butchers soon after they had left the meat line at a meat products factory, but was not detected on the finger-tips of 100 volunteers at the Central Public Health Laboratory.

The implications of the present findings to the spread of salmonellas from raw to cooked foods, and the relevance of this to outbreaks of Salmonella infection in the general population and in hospitals, are discussed.

A total of 1537 strains of Salmonella typhimurium belonging to seven prevalent phage types were examined on solid media for their ability to ferment rhamnose, xylose and inositol, for colicine production and for nutritional requirements. Most of the strains in each phage type were almost completely homogeneous, especially in their sugar fermentation reactions. However, strains of phage type 1a/2 were not homogeneous, but could be assigned to one of four subgroups on the basis of ability to ferment inositol, inhibition of growth by meso-tartrate and auxotrophy for nicotinic acid. The subdivision proved to have epidemiological value. The inhibition of growth by meso-tartrate was observed on a denned medium containing citrate as the energy source. Inhibition did not occur if glucose, casein hydrolysate or aspartic acid were added to the medium.

In terms of the rate of positive diagnoses the indirect fluorescent antibody (FA) test was rather more effective than iodine for demonstrating trachoma (TRIC) inclusions in conjunctival scrapings, but the degree of advantage was not statistically significant. In duplicate scrapings stained at random by one or the other method, FA staining yielded the higher inclusion count significantly more often than did iodine. Some inclusions that failed to stain with FA were found on subsequent staining with Giemsa. A method is described for improving the post-FA Giemsa staining of conjunctival smears stored at subzero temperatures. Given adequate facilities, the FA stain is preferable to iodine for demonstrating TRIC inclusions in the conjunctiva; but the iodine method, properly used, holds advantages for field use.

For isolating trachoma (TRIC) agent from conjunctival scrapings, both streptomycin and neomycin were effective in preventing bacterial contamination, but at high concentrations neomycin was rather more inhibitory to TRIC agent. Prolonging storage of scrapings with neomycin at 4° from 30 min. to 24 hr. reduced the bacterial contamination rate, but also diminished the chance of isolating TRIC agent at the 1st passage. Two freshly isolated TRIC agents differed in their susceptibility to neomycin and streptomycin. Kanamycin and framycetin appeared to be less suitable than streptomycin for use in isolation of TRIC agent. In isolation studies, the possibility of inhibiting TRIC agent by high concentrations of antibotics, including streptomycin, should be borne in mind.