Abstract
BACKGROUND: Parvovirus B19 (B19V) infection occurs worldwide seasonally, especially in school-age children. Due to limited surveillance, clinicians report an increase of cases to identify outbreaks, while labs determine seropositivity rates. In 2024, B19V outbreak occurred in Türkiye and many other countries. AIMS: To estimate incidences of B19V infection in Türkiye from 2020 to 2024 using National Infectious Disease Surveillance and Early Warning System (IZCI) and to determine case fatality rate (CFR) during the 2024 outbreak period. STUDY DESIGN: Retrospective descriptive study. METHODS: The number of cases was obtained from the syndromic surveillance of rash diseases in national database. All notifications with International Classification of Diseases, 10th Revision diagnosis code "erythema infectiosum" within the syndromic surveillance were included in the study. All age groups were included in the study and no specific group was excluded. Annual estimated incidences were calculated for past 5 years. The distribution of cumulative incidence for the outbreak by age group and geographical regions was analysed. CFR was calculated for the outbreak period by using the proportion of people who have been diagnosed with B19V. Disease indicators were calculated as crude rates. RESULTS: The estimated incidence in 2024 was 15.24 per 100,000. The peak of the outbreak was in May. The regions with the highest cumulative incidences during the outbreak period were the Black Sea, Marmara, and Central Anatolia. The highest cumulative incidence was 102.64 per 100,000 in 5-9 age group. The CFR was calculated as 0.0184% in the outbreak with 2 deaths out of 10,898 cases. CONCLUSION: Türkiye has experienced the largest B19V outbreak between February and June 2024. This study showed the unusual scale of B19V post-pandemic, suggesting that such outbreaks can be expected after pandemics. The establishment of syndromic surveillance has proved critical for early outbreak detection and response.