In 1882 Robert Koch reported the isolation of tuberkelbazillen from human and bovine sources. Sixteen years later, Theobald Smith (1898) demonstrated that strains of Koch's tubercle bacilli from these two hosts differed in cell morphology, cultural characteristics and virulence in rabbits. He did not believe that these variants were limited to the hosts from which they were isolated nor that the differences resulted from adaptations to a given host. Indeed, he remarked that ‘It might be better to omit the host designation of such varieties in order to anticipate assumptions that they are necessarily limited to the host whose name they bear.’ Nevertheless, heedless of his own misgivings he termed them the ‘human’ and ‘bovine’ types.

It might seem very late to suggest, nearly 400 years after the first clinical description of influenza and 54 years after its isolation (reviewed by Stuart-Harris. Schild & Oxford, 1985), that many fundamental questions remain to be answered about the virus itself. However the precise antigenic and biochemical structure of the natural field virus has not been established. If so much remains to be learned concerning the nature of the virion then perhaps it may be less surprising that there are some conflicting theories as regards influenza epidemiology. Such questions are raised in the current volume of the journal where Hope-Simpson & Golubev (pp. 5 54) propose a major role for virus persistence in the human disease and, a lesser role for a linked chain of acute infection spreading influenza around the world (see also Hope-Simpson. 1979: 1981). This would be a minority view of the epidemiology of influenza A at present and is most definitely in conflict with the orthodox idea of person to person spread in an endless chain.

In his book, Floating Matter of the Air, John Tyndall (Tyndall, p. 262) quotes from Robert Boyle's ‘Essay on the Pathological Part of Physik’ ‘that he who thoroughly understands the nature of ferments and fermentations shall probably … give a fair account of divers phenomena of several diseases, which will perhaps be never properly understood without an insight into the doctrine of fermentations'. It was more than a century and a half before the first part of this suggestion was fulfilled, after which the unravelling of the causes of infective diseases proceeded rapidly. In 1836 de la Tour and, almost simultaneously, Schwann (Tyndall, p. 7) discovered, in yeast, the agent of fermentation as a living organism which reproduced itself in endless succession. Schwann also observed that putrefaction in meat broth did not set in if this was kept in contact, not with ordinary air, but with air which had been previously brought to a high temperature.

Forty-one clinical isolates of Legionella pneumophila from sporadic cases of legionella pneumonia were collected from laboratories throughout the United Kingdom and were compared with 300 routine environmental isolates using two panels of monoclonal antibodies, covering serogroups 1–10. Eighty-five per cent of the clinical isolates belonged to the subgroup Pontiac of serogroup 1, whilst only 13% of the environmental isolates did. Approximately half of the clinical isolates tested came from patients with a recent history of foreign travel, mainly to southern Europe.

Influenza A virus was discovered in 1933, and since then four major variants have caused all the epidemies of human influenza A. Each had an era of solo world prevalence until 1977 as follows: H0N1 (old style) strains until 1946. H1N1 (old style) strains until 1957, H2N2 strains until 1968. then H3N2 strains, which were joined in 1977 by a renewed prevalence of H1N1 (old style) strains.

Serological studies show that H2N2 strains probably had had a previous era of world prevalence during the last quarter of the nineteenth century, and had then been replaced by H3N2 strains from about 1900 to 1918. From about 1907 the H3N2 strains had been joined, as now. by H1N1 (old style) strains until both had been replaced in 1918 by a fifth major variant closely related to swine influenza virus A/Hswine1N1 (old style), which had then had an era of solo world prevalence in mankind until about 1929. when it had been replaced by the H0N1 strains that were first isolated in 1933.

Eras of prevalence of a major variant have usually been initiated by a severe pandemic followed at intervals of a year or two by successive epidemics in each of which the nature of the virus is usually a little changed (antigenic drift), but not enough to permit frequent recurrent infections during the same era. Changes of major variant (antigenic shift) are large enough to permit reinfection. At both major and minor changes the strains of the previous variant tend to disappear and to be replaced within a single season, worldwide in the case of a major variant, or in the area of prevalence of a previous minor variant.

Pandemics, epidemics and antigenic variations all occur seasonally, and influenza and its viruses virtually disappear from the population of any locality between epidemics, an interval of many consecutive months. A global view, however, shows influenza continually present in the world population, progressing each year south and then north, thus crossing the equator twice yearly around the equinoxes, the tropical monsoon periods. Influenza arrives in the temperate latitudes in the colder months, about 6 months separating its arrival in the two hemispheres.

None of this behaviour is explained by the current concept that the virus is surviving like measles virus by direct spread from the sick providing endless chains of human influenza A. A number of other aspects of the human host influenza A virus relationship encountered in household outbreaks are among the list of 20 difficulties that are inexplicable by the current concept of direct spread.

Alternative concepts have usually been designed to counter particular difficulties and are incompatible with other features of influenzal behaviour in mankind. The new concept detailed in the appendix provides simple explanations for most if not all of the difficulties. It proposes that influenza A virus cannot normally be transmitted during the illness because it too rapidly becomes non-infectious in a mode of persistence or latency in the human host. Many months or a year or two later it is reactivated by a seasonally mediated stimulus which, like all seasonal phenomena, is ultimately dependent on variations in solar radiation caused by the tilt of the plane of earth's rotation in relation to that of its circumsolar orbit. The carriers, who are always widely seeded throughout the world population, become briefly infectious and their non-immune companions, if infected, comprise the whole of the next epidemic. The reactivated virus particles must encounter the immunity they have engendered in the carrier, thus allowing minor mutants an advantage over virions identical with the parent virus, and so favouring antigenic drift and automatic disappearance of predecessor and prompt seasonal replacement. Antigenic shift and recycling of major variants may also be explained by virus latency in the human host.

In November 1986 a large-scale survey was undertaken in the Gloucestershire town of Stonehouse during an outbreak of meningococcal disease due to group B type 15 subtype Pl. 16 sulphonamide-resistant strains. There were 15 cases in Stonehouse residents during the 4 years from April 1983, an annual attack rate of 56·5 per 100000. Four secondary cases occurred despite rifampicin prophylaxis. The objectives of this community survey were to investigate patterns of meningococcal carriage, transmission and immunity and to determine the proportion of non-secretors of blood group antigens in the Stonehouse population find amongst meningococcal carriers. A total of 6237 subjects participated including 75% of the 6635 Stonehouse residents. Over 97% of the participants provided all three of the requested specimens – nasopharyngeal swabs, saliva and blood samples.

The co-operation between the many organizations involved in the detailed preliminary planning was instrumental in the success of the survey; in particular the value of effective collaboration between Departments of Community Medicine and Microbiology and of the Public Health Laboratory Service network of laboratories in undertaking investigations of this size and type was clearly demonstrated.

A comparison was made between membrane filtration and centrifugation for the isolation of Legionella pneumophila from seeded water samples. Using samples of varying concentration, the optimum speed and time of centrifugation were determined and the relationship between the number of organisms present in the water and the proportion recovered was examined. Following this, sequential routine environmental waters were filtered and centrifuged in parallel.

Centrifugation and filtration using nitrocellulose filters were found to be comparable. The optimum speed and time of centrifugation was approximately 6000 g for 10 min. There was a constant proportion of viable organisms recovered irrespective of the concentration in the unspun samples.

Enzyme immunoassays (EIA) for IgG and IgM antibodies against influenza A and B virus are described. One hundred and seven subjects with a clinical diagnosis of acute respiratory infection (influenza, bronchitis or pneumonia) were selected for this study during two epidemics of influenza A which occurred in Finland in 1983 and 1985. Paired sera and nasopharyngeal secretions were obtained from all subjects. The sera were tested for influenza A and B antibodies by IgG and IgM EIAs and by complement fixation tests. The nasopharyngeal secretions were tested by an indirect EIA for influenza A and B antigens.

The IgG EIA was found to be better than complement fixation for the diagnosis of influenza A infections: only 22% of the significant increases detected by this test were also positive by complement fixation. The additional contribution of the IgM EIA to the number of positives was minimal.

It was also found that testing a single 1/1000 dilution of serum for influenza A and 1/100 dilution for influenza B in the IgG EIA gave as many positives as the conventional method of testing several dilutions.

A total of 6234 nasopharyngeal swabs was collected during a survey of the population of Stonehouse, Gloucestershire in November 1986 as part of an investigation into an outbreak of meningococcal disease. The overall meningococcal carriage rate was 10·9%. The carriage rate rose with age from 2·1% in the 0- to 4-year-olds to a peak of 24·5% in the 15- to 19-year-olds, and thereafter declined steadily with age. Male carriers outnumbered female carriers of meningococci by 3:2. Group B (or non-groupable) type 15 sulphonamide-resistant strains which had caused the outbreak were isolated from 1·4% of subjects. The age distribution of carriers of these strains was similar to that of other meningococci apart from an additional peak in the 5–9-year age group and a more rapid decline in carriage with increasing age. Variations in the carriage rates of the outbreak strain were seen in children attending different schools and in the residents of different areas of the town. The low carriage rate of these strains in a community during a prolonged outbreak supports the hypothesis that these organisms are less transmissible but more virulent than other strains of pathogenic meningococci.

Carriage of Neisseria lactamica, which is thought to be important in the development of meningococcal immunity, was most frequent in children under the age of 5 years and was six times commoner in this age group than carriage of Neisseria meningitidis. In older children and adults female carriers of N. lactamica increasingly outnumbered males in contrast to the male preponderance observed with meningococcal carriage.

A food-borne outbreak of sore throat caused by Lancefield group G β-haemolytic streptococci and involving 50 persons occurred in May 1983 in an Israeli military camp. All of the patients available for clinical examination had sore throat and difficulty in swallowing. Exudative tonsillitis occurred in 46% of the patients and the body temperature was above 37·5 °C in 81%. The pattern of attack was uniform over the base and 37 became ill during the night and morning of the 5 May. Thirty-two (84%) of the throat cultures taken from 37 patients grew group G β-haemolytic streptococci. Eight of 29 contacts were positive for group G β-haemolytic streptococci and 6 of the 28 foodhandlers examined had positive cultures of the same group. The organism was also isolated from one food sample. The epidemiological and laboratory investigations indicated that a food handler, a convalescent carrier of group G streptococci, might have been the source of infection. Assumptions on the potential of non-group A streptococci to cause epidemics are discussed.

Mathematical models and statistical analyses of epidemiological data are employed to assess the potential impact of mass vaccination on the incidences of cases of mumps infection and cases of mumps related complications. The analyses reveal that in the United Kingdom the average age at infection with the mumps virus is currently between 6–7 years and that the inter-epidemic period of the infection is approximately 3 years. The critical level of vaccine uptake to eliminate mumps virus transmission is predicted to be approximately 85% of each cohort of boys and girls by the age of 2 years. Analyses of published data show that the risk of complication arising from mumps infection is markedly age- and sex-related. Model predictions suggest that the incidence of orchitis will be increased, over the level pertaining prior to mass vaccination, by levels of vaccine uptake (by 2 years of age) that are less than 70% of each yearly cohort of boys and girls. Moderate (over 00%) to high (75%) levels of vaccine uptake, however, are predicted to reduce the overall incidence of cases of mumps related complications (especially those with CNS involvement).

Group L, β-haemolytic streptococci can cause infection in dogs, pigs, cattle and sheep but there have been very few reports in man. In studies of skin infection in meat handlers we cultured group L streptococci from clinically infected wounds, impetigo and paronychia of 15 patients involved in the slaughter and processing of chickens and pigs. Staphylococcus aureus was also present in eight (53%) of the lesions. At least five other infections with group L streptococci in meat and animal handlers are known to have occurred in other parts of England in recent years, and brief details are given.

Multiply- and methicillin-resistant Staphylococcus aureus (MRSA) strains have been isolated from five small outbreaks of nosocomial infection in five different hospitals. The MRSA were typed by phage patterns, biochemical traits, resistance phenotypes and plasmid patterns. Three different groups of strains can be distinguished. The MRSA from three outbreaks in one country share identical characters.

Phage typing by the use of the International Basic Set for Phage Typing staphylococci as well as experimental phages does not completely discriminate between the strains. Attribution of several resistance determinants to plasmids in two of the described strain groups proved valuable for strain differentiation.

These multiply-resistant strains are sensitive to vancomycin and to rifampicin.

This study compares the presence and level of measles haemagglutination inhibiting antibody in the sera of primary school children in selected rural and urban areas of Kaduna State, Nigeria following a vaccination campaign. The results, analysed by Mann-Whitney statistical test at α=0·05, showed significantly higher levels of haemagglutination inhibiting antibody in all the age groups in urban areas when compared with rural areas. The implications of these findings on measles vaccination campaigns are discussed.

A simple impression-plate technique has been used to investigate the survival of four thermophilic campylobacter strains applied to fingertips. Campylobacters suspended in 0·1% peptone water and dried on the fingertips survived for different periods of time ranging from < 1 to ≧ 4 min. However, campylobacters suspended in chicken liquor or blood survived for much longer periods. The most resilient organism was Campylobacter jejuni NCTC 11392 which, when suspended in 50% horse blood, survived for an hour. Suspensions containing 106–107 organisms prepared in 50% blood and dried on to fingertips were removed by thorough hand washing with either soap and water or water alone followed by drying on paper towels, but persisted on wet hands. The organisms were also eliminated by wiping the hands with a tissue saturated with 70% isopropyl alcohol for 15 sec.

Fifty-four strains of Escherichia coli belonging to serogroup O 157 were examined for the production of Vero cytotoxins VT1 and VT2, and for other properties such as plasmid content, resistance to antimicrobial agents and colicin production. Twenty-six strains from cases of diarrhoea, haemorrhagic colitis and haemolytic uraemic syndrome in humans produced VT. By serum neutralization tests and hybridization with DNA probes for VTl or VT2, three classes were recognized which produced either VTl alone or VT2 alone or both VTl and VT2. These strains were of H type 7 or non-motile. The strains producing VT were sensitive to all the antimicrobial agents tested, and all carried at least one plasmid which had a molecular weight of c.60 × 106. Seven strains of porcine origin and 21 strains of human origin did not produce VT or hybridize with either DNA probe. None of these strains was of H type 7. Of the 21 human VT” strains, 17 were of extraintestinal origin and 18 were of H type 45. Twenty-three of the 28 VT” strains were resistant to at least one antimicrobial agent.

In 1978, 22 staff members of the National Institute of Virology, Pune, India, were given two doses of human diploid cell antirabies vaccine (HDCV) for primary pre-exposure prophylactic immunization; the interval between the two doses being approximately 4 weeks. Eighteen of these 22 vaccinees were given a booster dose 1 year later. All 18 vaccinees developed protective levels of antibody; most of them had antibody levels exceeding 10 IU/ml.

In 1984, 5 years after the booster dose, 11 (79·0%) of 14 vaccinees tested still possessed neutralizing antibody levels ranging from 0·5 IU/ml to 10 IU/ml. Fourteen days after the administration of a booster dose, the antibody levels ranged from 10 to ≥ 100 IU/ml for all except one vaccinee (5·2 IU/ml). These findings demonstrate that the majority of vaccinees retained detectable neutralizing antibody after pre-exposure prophylaxis for as long as 5 years and that a single booster dose thereafter evoked a good antibody response.

An analysis of the serological and biochemical typing results of 925 clinical isolates of klebsiella revealed that biotyping and serotyping of klebsiella could replace each other for epidemiological purposes. The combination of both typing methods provided even more epidemiological information in analysing clusters of particular serotypes and biotypes in time. Clustering serotypes, mainly of neonatal origin, were nearly uniformly more resistant to the antibiotics in common use than other serotypes. Biotyping as well as serotyping of klebsiella isolates recovered from environmental surveys in the neonatal ward showed that epidemic and non-epidemic klebsiella isolates could occasionally be cultured from the environment and from the staff.

The distribution of serogroups of thermophilic campylobacters isolated in Israel from human patients (2421 isolates), chicken (942), turkeys (158), cattle (398), wild birds (234) and other sources, was studied.

Among the human isolates, 74 ROG-serogroups were identified. The six most commonly isolated of these (1,18; 11; 12; 8,23; 4 and 5,39) were found frequently in chickens. Only four common serogroups in man were also common in cattle, three in turkeys and two in wild birds.

Two common serogroups in man (1,18 and 5,39) were prevalent all over the country, while others were regionally distributed. When the prevalence of different serogroups in Israel was compared to that in Canada, some groups were common to both countries and others were common in only one or the other.

Campylobacter jejuni accounted for 86·7% to 92·1% of the isolates from man, chickens, turkeys, cattle and most of the wild birds. C. coli was found in 34·4% of isolates from cattle egrets and in 70·5% of those from pigs.