1. World Health Organization. https://www.who.int/bulletin/online_first/COVID-19/en/
2. https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus
3. World Health Organization. Virtual press conference on COVID-19 – 11 March 2020. https://www.who.int/docs/default-source/coronaviruse/transcripts/who-audio-emergencies-coronavirus-press-conference-full-and-final-11mar2020.pdf
4. https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html
5. https://www.who.int/publications/m/item/weekly-epidemiological-update---23-february-2021