EPIDEMIOLOGIC CHARACTERISTICS OF RESPIRATORY SYNCYTIAL VIRUS OUTBREAKS IN ZAGREB DURING TWO CONSECUTIVE WINTER SEASONS

Akutne infekcije dišnog sustava (IDS) jedan su od vodećih uzroka pobolijevanja i smrtnosti u svijetu. Cilj ovog istraživanja bio je odrediti epidemiološke značajke RSV infekcija u djece na području Grada Zagreba i Zagrebačke županije tijekom dviju uzastopnih zimskih sezona 2012./13. te 2013./14. godine, te posebice utvrditi epidemijske vrhunce i usporediti ih s dosadašnjim spoznajama o ustaljenom ciklusu pojavljivanja RSV epidemija. Ovo istraživanje obuhvatilo je 2158 bolesnika u dobi 0-5 godina, sa simptomima akutne infekcije dišnog sustava (IDS), od čega je 504 (23,3 %) imalo infekciju uzrokovanu RSV-om. Od svakog bolesnika uzet je nazofaringealni sekret ili obrisak nazofarinksa u kojem je dokazan RSV metodom izravne imunofl uorescencije. Tijekom zimske sezone 2012./13. godine bilo je 294 (27,5 %) bolesnika s dokazanom RSV infekcijom, a 2013./14. bilo ih je 210 (19,3 %). Najveći broj oboljele djece bio je u dobi 0-6 mjeseci (233/46,2 %). Najčešće je zabilježen sindrom bronhiolitisa (221; 43,8 %). Vrhunac RSV epidemije tijekom 2012./13. bio je u siječnju/veljači 2013. godine (92/98 oboljelih), a u sezoni 2013./14. bio je u veljači/ožujku 2014. godine (87/82 oboljela). Veliku epidemiju pratio je veći broj dokazanih slučajeva RSV (294) te veća učestalost bronhiolitisa u dojenčadi (62,4 %) nego malu (210 slučajeva, odnosno 50,7 % bronhiolitisa u dojenčadi). Naši rezultati su u skladu s prethodnim zapažanjima koja su pokazala da epidemije RSV u Hrvatskoj imaju dvogodišnji ciklus.Respiratory syncytial virus (RSV) is the most important viral agent causing severe acute respiratory tract infections (ARTI) in infants and young children. The aim was to investigate the epidemic pattern of RSV outbreaks in children in the City of Zagreb and Zagreb County during two consecutive winter seasons 2012-2014, to defi ne the peaks of outbreaks and to compare them with previous observation on RSV epidemics occurring in two-year cycles in Croatia. The survey included 2158 patients aged 0-5 years with ARTI. Study period included two consecutive winter seasons 2012-2014. Samples of nasopharyngeal aspirate and/or swab were collected from each patient. The virus was detected using commercial monoclonal antibodies in direct immunofl uorescence assay. Of 504 (23.3%) RSV infections identifi ed in children, there were 282 (56%) boys and 222 (44%) girls. During 2012/2013 and 2013/2014, RSV infection was diagnosed in 294 (27.5%) and 210 (19.3%) patients, respectively. RSV proved to be the causative agent of bronchiolitis in 221 (43.8%), upper respiratory tract infection in 183 (36.3%), pneumonia in 69 (13.7%), bronchitis in 21 (4.2%) and croup in 10 (2.0%) patients. Outbreak peaks during the 2012/2013 and 2013/2014 winter seasons were recorded in January/February 2013 (92/98 patients) and February/March 2014 (87/82 patients), respectively. There were 294 RSV cases and a higher incidence of bronchiolitis in infants (62.4%) during major RSV outbreak in contrast to minor outbreak (210 cases and 50.7% cases of bronchiolitis, respectively). Our results are consistent with previous observations that RSV outbreaks in Croatia have biennial cycles. RSV is a common causative viral agent of ARTI, especially in infants and in winter months. Therefore, RSV is still a signifi cant public health issue and it is necessary to detect the development of RSV outbreak in order to undertake prevention measures against the spread of infection