The System of Epidemiological Vigilance of Navarra comprises the notification of 33 transmissible infectious diseases, to which are added epidemic outbreaks of any etiology or cause. Notification to the system is carried out on a weekly basis by any doctor who suspects or diagnoses any of the processes. In our Autonomous Community, the Diseases of Compulsory Declaration (DCDs) are reported to the Section of Vigilance and Epidemiological Control of the Institute of Public Health, on a weekly basis by the doctors of Primary and Specialised Care. Subsequently, the information is sent to the National Centre of Epidemiology, where data from the Autonomous Communities is centralised. In 1998, with respect to the heading of diseases of respiratory transmission, the only disease that showed an epidemic index higher than 1 was Flu, with 44,666 reported cases, (Estimated Incidence: 1.15), and which has a clear seasonal component ñin the first 8 weeks of the year 67% of the cases corresponding to the yearly total were reportedñ with a maximum in week 4 with 6,361 reported cases. Fifteen cases of meningococcal disease were diagnosed, (Rate 2.88 cases per 100,000 inhabitants), lower to that declared in 1997 and the second lowest in the last 25 years after the rate of 2.31 in 1994. All of the cases were confirmed microbiologically and appeared in a sporadic way. With respect to the causative serogroup, on 9 occasions serogroup C was isolated, with the latter responsible for the death of a girl and an elderly woman. On 6 occasions Neisseria meningitidis serogroup B was isolated. By age group, 4 cases were declared in children under 2 years of age (46.1 per 100,000), nine cases in children between 2 and 19 years of age (8.65 per 100,000) and the two remaining cases in persons of 20 years or above (0.49 per 100,000). The predominant clinical form was sepsis in 9 cases and meningitis in the 6 remaining cases. Six cases of Legionnaire's disease were declared in 1998, all under the clinical form of pneumonia; these were isolated cases of middle-aged persons resident, in five cases, in different localities in the south of Navarra without any antecedents of travelling.