A health worker collects a swab from a woman for a COVID-19 test in the Congress Square in Ljubljana, Slovenia, on Dec. 22, 2020. Voluntary mass testing for coronavirus started in a number of Slovenian towns on Tuesday, with long lines reported in big towns. (Photos: Xinhua)

A woman sanitizes her hands before having a COVID-19 test in the Congress Square in Ljubljana, Slovenia, on Dec. 22, 2020. Voluntary mass testing for coronavirus started in a number of Slovenian towns on Tuesday, with long lines reported in big towns.

People wait in line to have COVID-19 tests in the Congress Square in Ljubljana, Slovenia, on Dec. 22, 2020. Voluntary mass testing for coronavirus started in a number of Slovenian towns on Tuesday, with long lines reported in big towns.

People wait in line to have COVID-19 tests in the Congress Square in Ljubljana, Slovenia, on Dec. 22, 2020. Voluntary mass testing for coronavirus started in a number of Slovenian towns on Tuesday, with long lines reported in big towns.

People wait in line to have COVID-19 tests in the Congress Square in Ljubljana, Slovenia, on Dec. 22, 2020. Voluntary mass testing for coronavirus started in a number of Slovenian towns on Tuesday, with long lines reported in big towns.

People wait to have COVID-19 tests in the Congress Square in Ljubljana, Slovenia, on Dec. 22, 2020. Voluntary mass testing for coronavirus started in a number of Slovenian towns on Tuesday, with long lines reported in big towns.

A man walks into a mobile testing unit in the Congress Square in Ljubljana, Slovenia, on Dec. 22, 2020. Voluntary mass testing for coronavirus started in a number of Slovenian towns on Tuesday, with long lines reported in big towns.

People wait in line to have COVID-19 tests in the Congress Square in Ljubljana, Slovenia, on Dec. 22, 2020. Voluntary mass testing for coronavirus started in a number of Slovenian towns on Tuesday, with long lines reported in big towns.