Changing patterns of communicable disease in England and Wales: part II-Disappearing and declining diseases

Modelling in infectious diseases: between haphazard and hazard

Modelling of infectious diseases is difficult, if not impossible. No epidemic has ever been truly predicted, rather than being merely noticed when it was already ongoing. Modelling the future course of an epidemic is similarly tenuous, as exemplified by ominous predictions during the last influenza pandemic leading to exaggerated national responses. The continuous evolution of microorganisms, the introduction of new pathogens into the human population and the interactions of a specific pathogen with the environment, vectors, intermediate hosts, reservoir animals and other microorganisms are far too complex to be predictable. Our environment is changing at an unprecedented rate, and human-related factors, which are essential components of any epidemic prediction model, are difficult to foresee in our increasingly dynamic societies. Any epidemiological model is, by definition, an abstraction of the real world, and fundamental assumptions and simplifications are therefore required. Indicator-based surveillance methods and, more recently, Internet biosurveillance systems can detect and monitor outbreaks of infections more rapidly and accurately than ever before. As the interactions between microorganisms, humans and the environment are too numerous and unexpected to be accurately represented in a mathematical model, we argue that prediction and model-based management of epidemics in their early phase are quite unlikely to become the norm.

Methicillin-resistant Staphylococcus aureus: a ten-year survey in a Dublin hospital

We undertook a retrospective, longitudinal survey to monitor the changing incidence, phage types and patterns of antibiotic resistance of methicillin-resistant Staphylococcus aureus (MRSA) in St Laurence's Hospital (SLH), Dublin over the last 10 years. Following a peak in 1979, the incidence of MRSA has gradually decreased to around 17% of S. aureus isolates in 1986, almost identical to its incidence 10 years before. However, the spectrum of antibiotic resistance among these organisms remains broad and this seems to be at least partially related to antibiotic usage. Many strains could not be phage typed and others were typable only by the additional phage 90. This has severely limited the usefulness of phage typing in the tracing of sources of outbreaks. Thus, there is a need for a more specific method of typing as well as a rational antibiotic policy, to successfully monitor and curtail the hospital spread of MRSA.

Epidemiology in general practice

Epidemiology in Country Practiceby William N. Pickles, published in 1939, has been a source of continuing interest and challenge especially to general practitioners (Watson, 1982; Booth, 1987). Pickles worked for over 50 years as a general practitioner (GP) in rural Wensleydale where there were many isolated villages in which natural immunity against various infections was often lacking. And so the source of infection could usually be traced, and, with little or no immunity, spread was often rapid.

Prevalence and pathogenesis of pneumoconiosis in coal workers

Dust dose and composition do not appear to account wholly for changes in the prevalence of coal workers' pneumoconiosis in Europe. In certain coal pits high progression evidently occurred with relatively low dust exposure or vice versa, whereas progression in relation to dust levels might be variable. Exceptionally high quartz concentrations occur in coal mine dust when pneumoconiosis may progress with unusual rapidity. Under such circumstances lesions resembling silicotic nodules may be found, but with the customarily lower levels of quartz the pathological features assume the form characteristic of coal workers. Morphological changes in relation to dust content of human and animal lungs, as well as cellular behavior, have not accounted completely for the epidemiological findings. Considering all the pathological evidence helps explain the pathogenesis of pneumoconiosis and vagaries of progression. The origin of progressive massive fibrosis cannot be explained simply in terms of dust burden or immunological features, and the role of an infective factor cannot be dismissed. Moreover, lipid secretion by alveolar epithelium introduces a new element that could affect the development of simple and complicated pneumoconiosis. In vitro, cytotoxicity appeared to be too variable for predictive purposes, though direct assay of fibrogenicity using the macrophage fibrogenic factor suggested that dust dose was more important than dust composition. Assessing individual susceptibility presents serious obstacles.

Health and health care among travellers

Travellers, or Gypsies, constitute a minority group with its own culture and traditions for whom access to health care can pose problems. A study of Traveller women and children showed that the sites where they lived were often lacking in facilities and provided a poor environment in terms of cleanliness and safety. Perinatal mortality was above average, and was especially high on sites with inadequate facilities and among the more mobile families. Immunisation and preventive care of children were both inadequate, especially among the more mobile. There continues to be a need for more, and better, permanent sites for Travellers. Other responses include allowing Traveller families to carry their own medical records, providing mobile clinics for Gypsy sites, and appointing specialist health visitors to ensure that Travellers get the heath care to which they are entitled.

Ten year mortality and causes of death in patients with rheumatoid arthritis

Five hundred men and 500 women, aged 40 or over, with rheumatoid arthritis, together with a control population matched for age and sex, were observed over 10 years. During that time 352 patients with rheumatoid arthritis (208 men, 144 women) and 221 controls (148 men, 73 women) died. The overall mortality was significantly higher (p less than 0.0001) in both men and women with rheumatoid arthritis than in the controls. Infections and cardiovascular and renal diseases (especially amyloidosis) appeared to be the main causes of death in rheumatoid arthritis.

Staphylococcus aureus bacteraemia: 400 episodes in St Thomas's Hospital

Four hundred episodes of Staphylococcus aureus bacteraemia occurred in St Thomas's Hospital from 1969 to 1983, accounting for 17.5% of all episodes of bacteraemia. The mortality was 24%, half attributable to underlying disease, and was highest in patients over 50. Almost 60% of the bacteraemias were acquired in hospital, and the source of the organism was generally obvious, with vascular access sites the most common (37%). Bone and joint infections accounted for 11.5% of episodes and endocarditis for 7%. Most staphylococci were resistant to penicillin only; three isolates were resistant to methicillin and five to fusidic acid. Microbiologists seldom influenced directly the choice of initial antibiotic treatment (though this usually conformed to the hospital's antibiotic prescribing policy) but had considerable influence over definitive treatment, usually cloxacillin or flucloxacillin alone or in combination with fusidic acid. S aureus bacteraemia is easy to identify and treat, though underlying disease may influence the outcome. Efforts should be made to prevent the largely iatrogenic disease.

Risks of zoonoses in a veterinary service

A survey was undertaken among the veterinary staff of the Ministry of Agriculture, Fisheries, and Food and the Institute for Research in Animal Diseases to estimate the distribution of occupationally acquired zoonoses in this population. A self-administered questionnaire was distributed to 1717 staff, 1625 (95%) of whom responded. It was observed that both laboratory and technical support staff were at risk from a variety of zoonotic infections, though generally to a lesser extent than veterinary surgeons. A history of injury while handling animals was reported frequently by veterinarians (45%). Accidental self-injection with vaccines was also commonly reported. It is suggested that both injury from animals and accidental self-injection are associated with the risk of zoonotic infection.