• Transmission of COVID 19 is primarily through inhaling the exhaled air of infected individuals.

• Epidemiological measures used to describe and investigate transmissibility include the basic and net reproduction numbers, the attack rate, and risk ratios.

• The incubation period is the time frame before the development of symptoms (4 to 6 days in average) and ranges from 0-14 days according to the WHO and 2-12 days according to ECDC.

• The infectious period is the time when an infected individual can transmit the infection. The infectious period of COVID-19 lasts 8-10 days in average (but can be longer depending on the case severity) and usually starts 1 to 3 days before the symptoms develop.

Determining the infectious period of COVID-19 is complicated by three factors:

• People can be diagnosed when they are symptomatic, pre-symptomatic, or asymptomatic,

• The standard diagnostic test, RT-PCR, is accurate for diagnosis as it can detect viral genetic material, but it cannot document when someone is no longer infectious because it cannot distinguish whether viral particles are still infectious or not,

• Cell culture is the best way to confirm whether an infectious Virus is present, but it takes time and requires specialized laboratory facilities.

• Symptoms of COVID 19 in mild cases include fever, sore throat, dry cough, malaise, and body aches or nausea, vomiting, abdominal pain, loose stools. Acute respiratory distress syndrome, shock, coagulation defects, encephalopathy, heart and kidney failure in severe cases.