Modeling Covid-19 dynamics for real-time estimates and projections: an application to Albanian data

Erida Gjini

For the parameters, average values were assumed based on the existing literature on COVID-19 (6; 7; 4). The basic reproduction number R 0 for COVID-19 transmission, denoting the number of new infections generated from a typical infected individual during the period of infectiousness, is expected to be between 1.7 and 2.6, (2) , and is the key target of control measures. The incubation time from exposure to infection, informing the progression rate τ , has been shown to be around 6.5 days (median), and up to 14 days (8) . Exposed individuals are assumed to not be infectious. After progressing to infection, a fraction of individuals are symptomatic given by φ, and 1 − φ are asymptomatic. The duration of infection from infected people in Wuhan has been observed to be around 11 days (7) , motivating my assumption of γ = 1/11 in the model, but larger and lower values have also been reported such as 20-30 days infectious period (9; 6) and 3.48 days (3) . In Albania, until March 28, more than 30 infected individuals have recovered, with typical viral shedding from onset of symptoms for about 6 days. The model assumes symptomatic individuals can progress to recovery or death with relative probability 1−f and f . It is assumed that asymptomatic individuals only experience mild infection and progress to recovery. Asymptomatic individuals transmit less infection, scaling their contribution by a factor k 2 (k 2 < 1).