1. known hypersensitivity/allergy to hydroxychloroquine or to 4-aminoquinoline compounds. 2. current use of hydroxychloroquine for the treatment of a medical condition. 3. known prolonged qt syndrome, or concomitant medications which simultaneously may prolong the qtc that cannot be temporarily suspended/replaced. these are including but not limited to class ia, ic and iii antiarrhythmics; certain antidepressants, antipsychotics, and anti-infectives; domperidone; 5-hydroxytryptamine (5-ht)3 receptor antagonists; kinase inhibitors; histone deacetylase inhibitors beta-2 adrenoceptor agonists. 4. known pre-existing retinopathy of the eye. 5. disclosure of self-administered use of hydroxychloroquine or chloroquine currently under investigation \<4 weeks prior to study. this window is intended to account for the drug half-life of hcq (21 days). 6. baseline symptom of covid-19 disease at enrollment and baseline viral detection specimen positive for sars-cov-2. all participants with covid-19 symptoms at enrollment will be directed to have confirmatory testing (within the department or occupational health as per the site guidelines). participants who are negative for sars-cov-2 will be redirected to enrollment procedures, those testing positive will be excluded.

1. known hypersensitivity/allergy to hydroxychloroquine or to 4-aminoquinoline compounds. 2. current use of hydroxychloroquine for the treatment of a medical condition. 3. known prolonged qt syndrome, or concomitant medications which simultaneously may prolong the qtc that cannot be temporarily suspended/replaced. these are including but not limited to class ia, ic and iii antiarrhythmics; certain antidepressants, antipsychotics, and anti-infectives; domperidone; 5-hydroxytryptamine (5-ht)3 receptor antagonists; kinase inhibitors; histone deacetylase inhibitors beta-2 adrenoceptor agonists. 4. known pre-existing retinopathy of the eye. 5. disclosure of self-administered use of hydroxychloroquine or chloroquine currently under investigation \<4 weeks prior to study. this window is intended to account for the drug half-life of hcq (21 days). 6. baseline symptom of covid-19 disease at enrollment and baseline viral detection specimen positive for sars-cov-2. all participants with covid-19 symptoms at enrollment will be directed to have confirmatory testing (within the department or occupational health as per the site guidelines). participants who are negative for sars-cov-2 will be redirected to enrollment procedures, those testing positive will be excluded.

known hypersensitivity/allergy to hydroxychloroquine or to 4-aminoquinoline compounds. current use of hydroxychloroquine for the treatment of a medical condition. known prolonged qt syndrome, or concomitant medications which simultaneously may prolong the qtc that cannot be temporarily suspended/replaced. these are including but not limited to class ia, ic and iii antiarrhythmics; certain antidepressants, antipsychotics, and anti-infectives; domperidone; 5-hydroxytryptamine (5-ht)3 receptor antagonists; kinase inhibitors; histone deacetylase inhibitors beta-2 adrenoceptor agonists. known pre-existing retinopathy of the eye. disclosure of self-administered use of hydroxychloroquine or chloroquine currently under investigation <4 weeks prior to study. this window is intended to account for the drug half-life of hcq (21 days). baseline symptom of covid-19 disease at enrollment and baseline viral detection specimen positive for sars-cov-2. all participants with covid-19 symptoms at enrollment will be directed to have confirmatory testing (within the department or occupational health as per the site guidelines). participants who are negative for sars-cov-2 will be redirected to enrollment procedures, those testing positive will be excluded.

known hypersensitivity/allergy to hydroxychloroquine or to 4-aminoquinoline compounds. current use of hydroxychloroquine for the treatment of a medical condition. known prolonged qt syndrome, or concomitant medications which simultaneously may prolong the qtc that cannot be temporarily suspended/replaced. these are including but not limited to class ia, ic and iii antiarrhythmics; certain antidepressants, antipsychotics, and anti-infectives; domperidone; 5-hydroxytryptamine (5-ht)3 receptor antagonists; kinase inhibitors; histone deacetylase inhibitors beta-2 adrenoceptor agonists. known pre-existing retinopathy of the eye. disclosure of self-administered use of hydroxychloroquine or chloroquine currently under investigation <4 weeks prior to study. this window is intended to account for the drug half-life of hcq (21 days). baseline symptom of covid-19 disease at enrollment and baseline viral detection specimen positive for sars-cov-2. all participants with covid-19 symptoms at enrollment will be directed to have confirmatory testing (within the department or occupational health as per the site guidelines). participants who are negative for sars-cov-2 will be redirected to enrollment procedures, those testing positive will be excluded.

1. known hypersensitivity/allergy to hydroxychloroquine or to 4-aminoquinoline compounds. 2. current use of hydroxychloroquine for the treatment of a medical condition. 3. known prolonged qt syndrome, or concomitant medications which simultaneously may prolong the qtc that cannot be temporarily suspended/replaced. these are including but not limited to class ia, ic and iii antiarrhythmics; certain antidepressants, antipsychotics, and anti-infectives; domperidone; 5-hydroxytryptamine (5-ht)3 receptor antagonists; kinase inhibitors; histone deacetylase inhibitors beta-2 adrenoceptor agonists. 4. known pre-existing retinopathy of the eye. 5. disclosure of self-administered use of hydroxychloroquine or chloroquine currently under investigation <4 weeks prior to study. this window is intended to account for the drug half-life of hcq (21 days). 6. baseline symptom of covid-19 disease at enrollment and baseline viral detection specimen positive for sars-cov-2. all participants with covid-19 symptoms at enrollment will be directed to have confirmatory testing (within the department or occupational health as per the site guidelines). participants who are negative for sars-cov-2 will be redirected to enrollment procedures, those testing positive will be excluded.

1. known hypersensitivity/allergy to hydroxychloroquine or to 4-aminoquinoline compounds. 2. current use of hydroxychloroquine for the treatment of a medical condition. 3. known prolonged qt syndrome, or concomitant medications which simultaneously may prolong the qtc that cannot be temporarily suspended/replaced. these are including but not limited to class ia, ic and iii antiarrhythmics; certain antidepressants, antipsychotics, and anti-infectives; domperidone; 5-hydroxytryptamine (5-ht)3 receptor antagonists; kinase inhibitors; histone deacetylase inhibitors beta-2 adrenoceptor agonists. 4. known pre-existing retinopathy of the eye. 5. disclosure of self-administered use of hydroxychloroquine or chloroquine currently under investigation <4 weeks prior to study. this window is intended to account for the drug half-life of hcq (21 days). 6. baseline symptom of covid-19 disease at enrollment and baseline viral detection specimen positive for sars-cov-2. all participants with covid-19 symptoms at enrollment will be directed to have confirmatory testing (within the department or occupational health as per the site guidelines). participants who are negative for sars-cov-2 will be redirected to enrollment procedures, those testing positive will be excluded.