Current participant inclusion criteria as of 03/06/2021: 1. Participant is willing and able to give informed consent for participation in the study and agrees with the study and its conduct 2. Agrees not to self-medicate with chloroquine, hydroxychloroquine or other potential antivirals 3. Adults (exact age is dependent on countries) less than 70 years old at the time of consent 4. Not previously diagnosed with COVID-19 5. Not currently symptomatic with an ARI 6. Participant is a healthcare worker or is a person at risk of contracting COVID-19. 7. Possesses an internet-enabled smartphone (Android or iOS) Previous participant inclusion criteria: 1. Willing and able to give informed consent for participation in the study and agrees with the study and its conduct 2. Agrees not to self-medicate with chloroquine, hydroxychloroquine or other potential antivirals 3. Adults (exact age is dependent on countries) <70 years old at the time of consent 4. Not previously diagnosed with COVID-19 5. Not currently symptomatic with an ARI 6. Working in a facility where there are cases of either proven or suspected COVID-19 7. Possesses an internet-enabled smartphone (Android or iOS)

Current participant inclusion criteria as of 03/06/2021: 1. Participant is willing and able to give informed consent for participation in the study and agrees with the study and its conduct 2. Agrees not to self-medicate with chloroquine, hydroxychloroquine or other potential antivirals 3. Adults (exact age is dependent on countries) less than 70 years old at the time of consent 4. Not previously diagnosed with COVID-19 5. Not currently symptomatic with an ARI 6. Participant is a healthcare worker or is a person at risk of contracting COVID-19. 7. Possesses an internet-enabled smartphone (Android or iOS) Previous participant inclusion criteria: 1. Willing and able to give informed consent for participation in the study and agrees with the study and its conduct 2. Agrees not to self-medicate with chloroquine, hydroxychloroquine or other potential antivirals 3. Adults (exact age is dependent on countries) <70 years old at the time of consent 4. Not previously diagnosed with COVID-19 5. Not currently symptomatic with an ARI 6. Working in a facility where there are cases of either proven or suspected COVID-19 7. Possesses an internet-enabled smartphone (Android or iOS)

1. Willing and able to give informed consent for participation in the study and agrees with the study and its conduct 2. Agrees not to self-medicate with chloroquine, hydroxychloroquine or other potential antivirals 3. Adults (exact age is dependent on countries) <70 years old at the time of consent 4. Not previously diagnosed with COVID-19 5. Not currently symptomatic with an ARI 6. Working in a facility where there are cases of either proven or suspected COVID-19 7. Possesses an internet-enabled smartphone (Android or iOS)

1. Willing and able to give informed consent for participation in the study and agrees with the study and its conduct 2. Agrees not to self-medicate with chloroquine, hydroxychloroquine or other potential antivirals 3. Adults (exact age is dependent on countries) <70 years old at the time of consent 4. Not previously diagnosed with COVID-19 5. Not currently symptomatic with an ARI 6. Working in a facility where there are cases of either proven or suspected COVID-19 7. Possesses an internet-enabled smartphone (Android or iOS)