[Etiology of atypical pneumonias in 2002. Results of the Croatian Institute of Public Health].

AIM: This investigation was performed at Department of Virology, Croatian National Institute of Public Health, the same diagnostic laboratory using the same serologic method as in earlier studies (in 1982 and 1992) to determine the incidence of the most common agents of atypical pneumonia in Croatia between January 1 and December 31, 2002.

PATIENTS AND

METHODS

The study included 630 patients from nearly all regions of Croatia with a clinical diagnosis of atypical pneumonia based on epidemiologic data, clinical symptoms, laboratory findings and chest X-rays. Most of them were from Zagreb (n = 370), followed by those from Slavonia, Istria, northwest Croatia, and Dalmatia. In all of them paired sera were collected at an interval of two weeks or more and tested for complement-fixing (CF) antibodies against the most common causative agents of the atypical pneumonia syndrome using CF test (micromethod).

RESULTS

An etiologic diagnosis was established in 25% (158/630) patients (81 male and 77 female). Respiratory viruses were the most frequently demonstrated pathogens in 2002, accounting for 72% of cases (adenoviruses 47%, parainfluenza viruses 14%, influenza viruses 9% and respiratory syncytial virus (RSV) 2%). These were followed by Chlamydophila (C.) psittaci; (19%), Mycoplasma (M.) pneumoniae; (6%) and Coxiella (C.) burnetii (3%). There were 3 cases of double infection: a combination of adenovirus and M. pneumoniae, of RSV and parainfluenza virus, and of RSV and M. pneumoniae in one patient each. Adenoviral, mycoplasmal and psittacosal pneumonia occurred throughout the year; influenza and most of RSV pneumonias occurred in winter months. Parainfluenza viruses caused pneumonias throughout the year but were more common in winter months. CF test does not distinguish type-specific antibodies to parainfluenza viruses. In March, a small epidemic of psittacosis (11 patients) was registered in the Split area while was responsible for the high incidence of psittacosal pneumonia in 2002. While M. pneumoniae-caused pneumonia occurred mainly in children and adolescents, viral pneumonias were distributed across all age groups. Psittacosal pneumonia occurred in only one child but was more common in adolescents and especially adults. Q-fever pneumonia occurred only in adults.