Yersinia enterocolitica biotype 4, serotype 0:3 is by far the most common human pathogenic Yersinia enterocolitica subtype in Scandinavia. It is extraordinarily immunologically specific, and an elevated antibody titre greater than or equal 80-160 is known to indicate acute infection. This titre was measured in five population surveys conducted in 1967-78, including 3278 examined adult men and women. The prevalence of titre elevation greater than or equal to was 1.0% in 1967. In 1978 it was significantly higher, 7.7%, and also the individual course of the titre in a ten-year longitudinal survey showed a significant increase in this prevalence, indicating an increasing incidence of infection. Significant sex and age differences were seen, women and younger subjects being more frequently affected than men and older subjects. The prevalence of elevated titre showed a seasonal variation with a maximum in the spring and autumn.

would infringe on the freedom of choice of the individual. Nor can the argument about difficulties in enforcement be used as an excuse, since infringement is so easy to detect. When seat-belt legislation was introduced in the State of Victoria' the majority of people complied without enforcement being necessary. The Australian experience has a number of other useful lessons for us. It was only as a result of strong pressure from the doctors that seat-belt legislation was introduced. In Victoria all road traffic accident casualties are required by law to have a blood alcohol test taken. This has allowed a much more accurate appraisal to be made of the very significant contribution of alcohol to the road accident problem. We may well have a good record in road accident deaths and injuries when compared with other countries. We have also made a great deal of progress in road safety. There is still so much more that we could do by relatively simple legislation and by tightening up of some of our existing laws. GORDON AVERY Harbury, Warwicks CV33 9HG

Sarcoidosis of recent onset was diagnosed during a Yersinia enterocolitica infection in seven patients at the Copenhagen County Hospitals during a 3 1/2 year period. In all cases the diagnosis was made from clinical symptoms and confirmed by chest X-ray and biopsy. In five of the patients a fourfold rise or decrease was measured in the antibody titre against Yersinia enterocolitica, serotype 3, confirming an acute infection. In another two patients this titre remained significantly elevated greater than or equal to 80, indicating chronic infection. Five patients experienced joint symptoms and four erythema nodosum, symptoms common to both yersiniosis and sarcoidosis. A follow-up examination 14 to 41 months after the debut of sarcoidosis showed total remission (including chest X-ray and respiratory function) in five of the seven patients. Recent research has shown that Yersinia enterocolitica following the early stage of the infection causes granulomatous lesions in lymph follicles, and this aetiology should thus be considered as a differential diagnosis to sarcoidosis.

The cellular immunity to Yersinia enterocolitica serotype 3 and crude human thyroid extract in 64 patients with thyroid diseases and 25 controls was studied by the leucocyte migration test. In the patient group as a whole and in patients with Graves' disease and nontoxic diffuse goitre a significantly reduced leucocyte migration towards Yersinia was found when compared with the controls. In controls the migration index was not related to the presence or titre of circulating yersinia antibodies, whereas the migration index of patients with yersinia antibodies was lower than the migration index of patients without yersinia antibodies as well as that of the controls. The leucocyte migration inhibition in two patients with recent yersinosis was normal during the recovery phase. In the presence of thyroid extract leucocyte migration inhibition differed only significantly in Graves' disease. However, a significantly positive correlation between inhibition of migration by thyroid extract and by Yersinia was found, while no correlation could be demonstrated in the controls. The cell-mediated immunity towards Yersinia in thyroid diseases thus demonstrated adds further evidence to the association between Yersinia and thyroid disease.