[Prevalence of ragweed hayfever in the south and east of the greater Lyon region in 1993].

In December 1993, AFEDA conducted an epidemiological survey in order to establish the prevalence of ragweed-induced pollinosis and to evaluate how well the public was informed about this danger. A survey by telephone was made, taking a random sample of the population drawn by lot from telephone directories in the Rhône district. This involved about 300,000 homes. Those in which at least one person was under 50 were questioned. The questionnaire included a section aimed at everyone, and another section aimed at homes where at least one person suffered from pollinosis in August and/or September, in Lyon. 1,800 homes were selected at random, 905 persons responded: 22.4% were off target, 77.6% matched up to the chosen target. Of these, 32.9% were aware of Ragweed and 31.9% knew of the dangers. The 702 homes targeted made a total of 2,060 persons, 59.6% of which live in town and 40.4% in suburban areas; 51.6% are women and 48.4% men. 53 people, i.e. 2.57%, presented at least one of the following symptoms in 1993: rhinitis 86.8%, conjunctivitis 69.8%, itching of the pharynx and/or ears 47.2%, tracheitis and/or asthma 41.5%. 77.4% received medication. In 1993, the prevalence of ragweed-induced symptoms is a certainty for 1.8% of the population, if we evaluate only those patients presenting these symptoms every year. This prevalence therefore does not take account of new cases nor of newcomers to the district. Moreover, we have probably under-estimated this prevalence, owing to the torrential rain that fell in Lyon in late August 1993. This made a break in the pollen curve, a phenomenon that has never yet been observed in 13 years of recording pollen calendars.