The serial and generation intervals from SARS-CoV-2 transmission dynamics and their potential application in the epidemiology of two citrus diseases

Since the start of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing the coronavirus disease 2019 (COVID-19) pandemic, the concepts of serial and generation intervals have been used as key epidemiological measures to understand the transmission dynamics of the disease. We carefully examined and repurposed these concepts to the understanding of the transmission chain and dynamics of two major citrus diseases: tristeza virus (caused by Citrus tristeza virus, CTV) and Huanglongbing (caused by Candidatus Liberibacter asiaticus). Following the fundamental definition of the concepts, the review delineates the transmission chain in the SARS-CoV-2 and that of CTV and CLas, pointing out their major similarities and differences. Then, it discusses estimation of the serial and generation intervals and their distributions for both plant diseases. Identification of infector-infectee tree pairs in a transmission chain within orchards is proposed through use of disease incidence data from intensive mapping, spatial pattern analysis, conditional probability, and simulation approaches. Like in SARS-CoV-2 dynamics, pre-symptomatic transmission in these two plant pathosystems is of epidemiological significance. Hence, estimation of the serial and generation interval can lay the foundations to understanding of early disease transmission dynamics, thus the implementation of vector control measures or eradication of infected trees. We hope this review motivates discussions on estimation and usage of these concepts to enhance understanding of the epidemiology of both of the herein examined citrus diseases.