Cattle and pig herds and flocks of domestic fowl have formed the main reservoir of human salmonella food poisoning in England and Wales from 1941 to 1972.

Changes in the incidence of human salmonella food poisoning and in the serotypes of salmonellas isolated from human infections are shown to have been associated with the introduction of new foods, with changes in animal husbandry, and with changes in the relative proportions of flesh food from different species consumed. New foods, dried powdered egg, liquid egg and frozen liquid egg were introduced during the period of food rationing which extended from 1940 to 1953. Changes in animal husbandry, in particular the intensive production of pigs, poultry and eggs, followed the re-establishment of pig herds and fowl flocks after the derationing of animal feed in 1953. The changes in the proportions of flesh foods consumed followed the introduction of frozen oven-ready fowl in the late 1950s and early 1960s which by 1964 became cheaper than traditional flesh foods.

Two strains of type SAT 2 foot-and-mouth disease virus which gave high titres of haemagglutinin activity reacted type-specifically in direct haemagglutinationinhibition tests with reference, bovine convalescent antisera. Comparisons of the haemagglutination-inhibition and the serum neutralization tests using cattle sera showed that both were equally specific and sensitive for detecting virus antibody.

The anticoagulant difenacoum was tested at two concentrations, 0·005 and 0·01%, in bait against warfarin-resistant rat infestations in farm buildings. Twelve out of the 14 treatments in which the lower concentration of the anticoagulant was used resulted in complete control. One of the remaining two treatments was probably also completely successful, but in the other a few rats, that were not eating the poisoned baits, were still active after 30 days of baiting. All six treatments done using the stronger concentration of poison were completely effective.

Since it took as long to control infestations with 0·01% as with 0·005% difenacoum in treatments carried out under similar conditions, the lower concentration is recommended for use against warfarin-resistant rats.

A total of 292 children's sera and 706 antenatal sera from different parts of England were tested for the presence of poliovirus neutralizing antibodies. Little variation was found between different areas and types of community, but a lower proportion of the 5–14 year old children had antibody than younger children and young adult women. The proportion of the young population with antibody, and the current acceptance rates for oral poliovirus vaccine are barely satisfactory.

A study of the distribution of subtypes ad and ay among sera from hepatitis B antigen-positive subjects in North West England and North Wales revealed a marked contrast between symptomless carriers among whom ad predominated and patients with acute hepatitis the majority of whom were ay. Those with hepatitis associated with drug addiction or other forms of ‘needle transmission’ were almost all of subtype ay. On the other hand in cases of ‘sporadic’ hepatitis without evidence of parenteral exposure subtypes ad and ay are about equally distributed.

These findings are similar to those reported from other countries in Northern Europe and North America. Although geographical and social factors clearly affect the distribution of the two subtypes it is suggested that the virus of subtype ay may be more readily transmitted than subtype ad by parenteral routes involving small amounts of blood.

Transferable chloramphenicol resistance has become common in the typhoid bacillus in countries such as Mexico, India, Vietnam and Thailand. Situations such as this, and others analogous to it in many parts of the world, are the result of the long-term indiscriminate use of chloramphenicol and other antibiotics in the affected areas. They can be rectified only by more rational antibiotic usage.

To assess the relative importance of different postulated modes of spread of hepatitis B in dialysis units, blood charged with various tracer organisms was used in simulated haemodialysis runs in four laboratories, and the resulting contamination of equipment and environment was measured semi-quantitatively.

Some airborne spread of the tracer organism occurred when tubing containing contaminated blood was needled as the ‘patient’ went on and came off the dialyser. Virtually no small airborne particles could be demonstrated however in simulated emergencies in which a blood line was disconnected, or even when bottles of blood were dropped on to a hard floor from a height of 2 metres.

Bacillus globigii spores from contaminated blood leaked in small numbers into the dialysing fluid through apparently intact coils. T3 phage, with a particle size of the same order as hepatitis B virus, passed in small quantities through the membrane of a Kiil dialyser from blood to dialysing fluid and also in the reverse direction when added to the header tank. A number of other dialysers were also permeable to phage.

Visual assessment of the appropriate moment for inserting the venous line into the ‘patient’ at the onset of dialysis was shown to be unreliable, as the displaced fluid from the end of the venous line was already contaminated before it contained visible red blood cells.

Considerable contamination of exposed surfaces and of the buttons on the proportionating unit cabinet occurred. Minor visible splashing of blood was a commonplace of the laboratory experiments and was shown to be also a common event during routine haemodialysis in two of the dialysis units taking part in the studies.