Turkiye Klinikleri Journal of Biostatistics

.: ORIGINAL RESEARCH
Estimation of the Time Dependent Reproduction Number of Novel Coronavirus (COVID 19) for Turkey in the Late Stage of the Outbreak
Türkiye İçin Salgının Geç Evresinde Yeni Tip Koronavirüsün (COVID-19) Zamana Bağlı Bulaştırma Katsayısının Tahmini
Serdal Kenan KÖSEa, Emre DEMİRb, Gülçin AYDOĞDUb
aDepartment of Biostatistics, Ankara University Faculty of Medicine, Ankara, TURKEY
bDepartment of Biostatistics, Hitit University Faculty of Medicine, Çorum, TURKEY
Turkiye Klinikleri J Biostat. 2021;13(1):103-11
doi: 10.5336/biostatic.2020-79473
Article Language: EN
Full Text
ABSTRACT
 Objective: Coronavirus disease-2019 (COVID-19), which caused a big outbreak, was first detected in Wuhan, China on 31st of December, 2019, and began to spread all over the world rapidly. The first case in Turkey was detected on the 11th of March, 2020. This study aims to calculate time-dependent (TD) reproduction number (Rt) using three different serial interval values in the late phase of the COVID-19 pandemic for Turkey. Material and Methods: TD model was used for estimation of reproduction number. For the serial interval of the coronavirus, the serial interval values of 4±2.5 and 6±3 days were used together with the severe acute respiratory syndrome and Middle East respiratory syndrome serial interval mean of 8±3.6. Gamma distribution was used for serial interval estimates. The bootstrap method with 1,000 simulations was used for all reproduction number confidence interval estimates. Results: Using 8±3.6, 6±3 and 4±2.5 serial interval values, the mean reproduction number (Rt) calculated for Turkey with the TD model was 2.06 (1.92-2.21), 1.70 (1.58-1.81), and 1.39 (1.30- 1.48), respectively. The confidence intervals of the reproduction number values calculated for Turkey range from 1.30 (lowest) to 2.21 (highest). Conclusion: According to the TD model results, from the first day when the pandemic started in Turkey to the 32nd (11th of April 2020) and 33rd (12th of April 2020) days, the Rt value decreased below 1 and the outbreak started to demonstrate a breaking point. Lower Rt in Turkey compared to the other epicenters of the world may indicate that Turkey was quicker in implementing preventive measures much earlier than the other countries.

Keywords: Coronavirus; COVID-19; reproduction number; outbreak; infectious disease; epidemiology; statistical modelling
ÖZET
 Amaç: Büyük bir salgına neden olan koronavirüs hastalığı2019 [coronavirus disease-2019 (COVID-19)], ilk olarak 31 Aralık 2019'da Çin'in Wuhan şehrinde ortaya çıktı ve hızlı bir şekilde tüm dünyaya yayılmaya başladı. Türkiye'de ilk vaka 11 Mart 2020'de tespit edildi. Bu çalışma, Türkiye için COVID-19 salgınının geç evresinde 3 farklı seri aralık senaryosu kullanarak, zamana bağlı [time dependent (TD)] bulaştırma katsayısını (Rt) hesaplamayı amaçlamaktadır. Gereç ve Yöntemler: Bulaştırma katsayısının tahmini için TD model kullanılmıştır. Koronavirüsün seri aralığı için şiddetli akut solunum sendromu ve Orta Doğu solunum sendromu seri aralığı ortalaması (8±3,6 gün) ile birlikte 4±2,5 ve 6±3 günlük seri aralık değerleri kullanılmıştır. Seri aralık tahmini için Gamma dağılımı kullanılmıştır. Bulaştırma katsayılarının güven aralığı tahminleri için 1.000 benzetim ile Bootstrap yöntemi kullanılmıştır. Bulgular: TD modeli ile Türkiye için 8±3,6, 6±3 ve 4±2,5 seri aralık değerleri kullanılarak hesaplanan ortalama bulaştırma katsayıları (Rt) sırasıyla 2,06 (1,92-2,21), 1,70 (1,58- 1,81) ve 1,39 (1,30-1,48) olarak bulunmuştur. Türkiye için hesaplanan bulaştırma katsayısı güven aralıklarının 1,30 (en düşük) ile 2,21 (en yüksek) arasında değiştiği belirlenmiştir. Sonuç: TD modeli sonuçlarına göre Türkiye'de salgının başladığı ilk günden sonra 32 (11 Nisan 2020) ve 33. (12 Nisan 2020) günlerde Rt değerinin ilk kez 1'in altına düştüğü ve salgının kırılmaya başladığı belirlenmiştir. Rt değerinin diğer ülkelere göre daha düşük olmasında diğer birçok ülkeden önce alınan önlemlerin etkili olduğu düşünülmektedir.

Anahtar Kelimeler: Koronavirüs; COVID-19; bulaştırma katsayısı; salgın; bulaşıcı hastalık; epidemiyoloji; istatistiksel modelleme
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