The Epidemiological Surveillance System of Navarra includes the notification of 34 transmissible infectious diseases, to which epidemic outbreaks of any aetiology and cause are added. In 2000, under the heading of diseases of respiratory transmission, 31,106 cases of flu were reported; 80% of total annual cases were reported in the first 6 weeks of the year, with a maximum in week 1 when 7,949 cases were reported. Twelve cases of meningococcal disease were reported to the system. Eight cases were confirmed microbiologically and appeared in a sporadic way. With respect to the causative serogroup, Neisseria meningitidis serogroup B was isolated on 5 occasions. On 2 occasions serogroup C was isolated, and serogroup Y was isolated on 1 occasion. By age groups, 5 cases were declared in infants of 2 years of age (Rate: 57.6 per 100,000), two cases in children between 2 and 4 years of age (14.7 per 100,000), one case in children between 5 and 9 years of age (3.5 per 100,000), two cases between 10 and 19 years of age (2.5 per 100,000) and the remaining 2 cases in persons aged 20 years or over (0.50 per 100,000). Twenty three cases of legionellosis were declared in 2000, all under the clinical form of pneumonia. These were isolated cases in persons of middle or advanced age. No indication was found of prior tourist trips to areas of high prevalence. In the majority of cases the origin was considered to be in the community, while one outbreak was identified as nosocomial. Similarly, there was a notable increase in the declaration of cases of hepatitis A, with 24 cases (EI: 2.00), pertussis, with 23 cases (EI: 1.64) and varicella, with 4,232 reported cases (EI: 1.86).