inclusion criteria: 1. males and females at least 18 years of age or of legal consenting age based on local requirements. 2. persons at increased risk of contracting covid-19, including: 1. healthcare workers with known direct occupational exposure to covid-19 within 7 days prior to enrollment. a qualifying person (i) provides healthcare to patients and/or (ii) typically positions themselves within 6 feet of patients ("close contact") and (iii) is a full- time employee (average of ≥ 24 hours/week) in a high contact area (emergency department, intensive care unit, covid-specific care unit, walk-in clinic, paramedic/first responder). 2. persons participating in social activities without the practice of generally accepted social distancing practices at least three times per week. qualifying activities include the presence of at least 10 people in close (\<6 feet) proximity to each other without masks or other personal protective equipment (e.g., socializing at bars or community/social centers, in-home social gatherings, classes or trainings, etc.). these subjects must have engaged in such activities at least three times in the past 7 days and plan to continue these activities during the study. 3. must have a smartphone, tablet, computer, or other qualifying internet- enabled device and daily internet access. 4. occupational exposure to a person infected with sar-cov-2 within 7 days prior to enrollment or social interaction as defined in criterion 2(b). 5. willing and able to provide written informed consent and comply with the requirements of the protocol, including completion of the subject diary.

inclusion criteria: 1. males and females at least 18 years of age or of legal consenting age based on local requirements. 2. persons at increased risk of contracting covid-19, including: 1. healthcare workers with known direct occupational exposure to covid-19 within 7 days prior to enrollment. a qualifying person (i) provides healthcare to patients and/or (ii) typically positions themselves within 6 feet of patients ("close contact") and (iii) is a full- time employee (average of ≥ 24 hours/week) in a high contact area (emergency department, intensive care unit, covid-specific care unit, walk-in clinic, paramedic/first responder). 2. persons participating in social activities without the practice of generally accepted social distancing practices at least three times per week. qualifying activities include the presence of at least 10 people in close (\<6 feet) proximity to each other without masks or other personal protective equipment (e.g., socializing at bars or community/social centers, in-home social gatherings, classes or trainings, etc.). these subjects must have engaged in such activities at least three times in the past 7 days and plan to continue these activities during the study. 3. must have a smartphone, tablet, computer, or other qualifying internet- enabled device and daily internet access. 4. occupational exposure to a person infected with sar-cov-2 within 7 days prior to enrollment or social interaction as defined in criterion 2(b). 5. willing and able to provide written informed consent and comply with the requirements of the protocol, including completion of the subject diary.

inclusion criteria: males and females at least 18 years of age or of legal consenting age based on local requirements. persons at increased risk of contracting covid-19, including: healthcare workers with known direct occupational exposure to covid-19 within 7 days prior to enrollment. a qualifying person (i) provides healthcare to patients and/or (ii) typically positions themselves within 6 feet of patients ("close contact") and (iii) is a full- time employee (average of ≥ 24 hours/week) in a high contact area (emergency department, intensive care unit, covid-specific care unit, walk-in clinic, paramedic/first responder). persons participating in social activities without the practice of generally accepted social distancing practices at least three times per week. qualifying activities include the presence of at least 10 people in close (<6 feet) proximity to each other without masks or other personal protective equipment (e.g., socializing at bars or community/social centers, in-home social gatherings, classes or trainings, etc.). these subjects must have engaged in such activities at least three times in the past 7 days and plan to continue these activities during the study. must have a smartphone, tablet, computer, or other qualifying internet- enabled device and daily internet access. occupational exposure to a person infected with sar-cov-2 within 7 days prior to enrollment or social interaction as defined in criterion 2(b). willing and able to provide written informed consent and comply with the requirements of the protocol, including completion of the subject diary.

inclusion criteria: males and females at least 18 years of age or of legal consenting age based on local requirements. persons at increased risk of contracting covid-19, including: healthcare workers with known direct occupational exposure to covid-19 within 7 days prior to enrollment. a qualifying person (i) provides healthcare to patients and/or (ii) typically positions themselves within 6 feet of patients ("close contact") and (iii) is a full- time employee (average of ≥ 24 hours/week) in a high contact area (emergency department, intensive care unit, covid-specific care unit, walk-in clinic, paramedic/first responder). persons participating in social activities without the practice of generally accepted social distancing practices at least three times per week. qualifying activities include the presence of at least 10 people in close (<6 feet) proximity to each other without masks or other personal protective equipment (e.g., socializing at bars or community/social centers, in-home social gatherings, classes or trainings, etc.). these subjects must have engaged in such activities at least three times in the past 7 days and plan to continue these activities during the study. must have a smartphone, tablet, computer, or other qualifying internet- enabled device and daily internet access. occupational exposure to a person infected with sar-cov-2 within 7 days prior to enrollment or social interaction as defined in criterion 2(b). willing and able to provide written informed consent and comply with the requirements of the protocol, including completion of the subject diary.

inclusion criteria: 1. males and females at least 18 years of age or of legal consenting age based on local requirements. 2. persons at increased risk of contracting covid-19, including: 1. healthcare workers with known direct occupational exposure to covid-19 within 7 days prior to enrollment. a qualifying person (i) provides healthcare to patients and/or (ii) typically positions themselves within 6 feet of patients ("close contact") and (iii) is a full- time employee (average of ≥ 24 hours/week) in a high contact area (emergency department, intensive care unit, covid-specific care unit, walk-in clinic, paramedic/first responder). 2. persons participating in social activities without the practice of generally accepted social distancing practices at least three times per week. qualifying activities include the presence of at least 10 people in close (<6 feet) proximity to each other without masks or other personal protective equipment (e.g., socializing at bars or community/social centers, in-home social gatherings, classes or trainings, etc.). these subjects must have engaged in such activities at least three times in the past 7 days and plan to continue these activities during the study. 3. must have a smartphone, tablet, computer, or other qualifying internet- enabled device and daily internet access. 4. occupational exposure to a person infected with sar-cov-2 within 7 days prior to enrollment or social interaction as defined in criterion 2(b). 5. willing and able to provide written informed consent and comply with the requirements of the protocol, including completion of the subject diary.

inclusion criteria: 1. males and females at least 18 years of age or of legal consenting age based on local requirements. 2. persons at increased risk of contracting covid-19, including: 1. healthcare workers with known direct occupational exposure to covid-19 within 7 days prior to enrollment. a qualifying person (i) provides healthcare to patients and/or (ii) typically positions themselves within 6 feet of patients ("close contact") and (iii) is a full- time employee (average of ≥ 24 hours/week) in a high contact area (emergency department, intensive care unit, covid-specific care unit, walk-in clinic, paramedic/first responder). 2. persons participating in social activities without the practice of generally accepted social distancing practices at least three times per week. qualifying activities include the presence of at least 10 people in close (<6 feet) proximity to each other without masks or other personal protective equipment (e.g., socializing at bars or community/social centers, in-home social gatherings, classes or trainings, etc.). these subjects must have engaged in such activities at least three times in the past 7 days and plan to continue these activities during the study. 3. must have a smartphone, tablet, computer, or other qualifying internet- enabled device and daily internet access. 4. occupational exposure to a person infected with sar-cov-2 within 7 days prior to enrollment or social interaction as defined in criterion 2(b). 5. willing and able to provide written informed consent and comply with the requirements of the protocol, including completion of the subject diary.