Source: https://www.afro.who.int/sites/default/files/Covid-19/Techinical%20documents/Strat%C3%A9gie%20harmonis%C3%A9e%20pour%20la%20surveillance%20aux%20points%20d%E2%80%99entr%C3%A9e%20les%20tests%20de%20laboratoire%20et%20la%20riposte%20transnationale%20%C3%A0%20la%20COVID-19%20.pdf