inclusion criteria: * subjects over 18 years old of any sex who work as health care workers, laboriously active during the recruitment of the study in health services that do not screen for the exclusion of acutely ill patients. * subjects who have not presented general symptoms such as general discomfort, fever, cough, dyspnoea or muscle pain in the last week. * subjects with negative covid-19 serological antibody diagnostic tests.

inclusion criteria: * subjects over 18 years old of any sex who work as health care workers, laboriously active during the recruitment of the study in health services that do not screen for the exclusion of acutely ill patients. * subjects who have not presented general symptoms such as general discomfort, fever, cough, dyspnoea or muscle pain in the last week. * subjects with negative covid-19 serological antibody diagnostic tests.

inclusion criteria: - subjects over 18 years old of any sex who work as health care workers, laboriously active during the recruitment of the study in health services that do not screen for the exclusion of acutely ill patients. - subjects who have not presented general symptoms such as general discomfort, fever, cough, dyspnoea or muscle pain in the last week. - subjects with negative covid-19 serological antibody diagnostic tests.

inclusion criteria: - subjects over 18 years old of any sex who work as health care workers, laboriously active during the recruitment of the study in health services that do not screen for the exclusion of acutely ill patients. - subjects who have not presented general symptoms such as general discomfort, fever, cough, dyspnoea or muscle pain in the last week. - subjects with negative covid-19 serological antibody diagnostic tests.