A medical worker collects a swab sample from a woman for the COVID-19 test in downtown Tunis, Tunisia, Dec. 21, 2020. The Municipal Government of Tunis carried out free rapid testing of COVID-19 in three densely populated areas of the city from Monday to Wednesday. (Photos: Xinhua)

A medical worker collects a swab sample from a woman for the COVID-19 test in downtown Tunis, Tunisia, Dec. 21, 2020. The Municipal Government of Tunis carried out free rapid testing of COVID-19 in three densely populated areas of the city from Monday to Wednesday.

A medical worker collects a swab sample from a man for the COVID-19 test in downtown Tunis, Tunisia, Dec. 21, 2020. The Municipal Government of Tunis carried out free rapid testing of COVID-19 in three densely populated areas of the city from Monday to Wednesday.

A medical worker collects a swab sample from a man for the COVID-19 test in downtown Tunis, Tunisia, Dec. 21, 2020. The Municipal Government of Tunis carried out free rapid testing of COVID-19 in three densely populated areas of the city from Monday to Wednesday.

Citizens wait for free COVID-19 test in downtown Tunis, Tunisia, Dec. 21, 2020. The Municipal Government of Tunis carried out free rapid testing of COVID-19 in three densely populated areas of the city from Monday to Wednesday.

Citizens wait for free COVID-19 test in downtown Tunis, Tunisia, Dec. 21, 2020. The Municipal Government of Tunis carried out free rapid testing of COVID-19 in three densely populated areas of the city from Monday to Wednesday.

Citizens wait for free COVID-19 test in downtown Tunis, Tunisia, Dec. 21, 2020. The Municipal Government of Tunis carried out free rapid testing of COVID-19 in three densely populated areas of the city from Monday to Wednesday.

A medical worker checks temperature for citizens waiting for free COVID-19 test in downtown Tunis, Tunisia, Dec. 21, 2020. The Municipal Government of Tunis carried out free rapid testing of COVID-19 in three densely populated areas of the city from Monday to Wednesday.