SARS-CoV-2

Background

Transmitted mostly by respiratory droplets, with some amount transmission via aerosols and little to no transmission via contact
First cases detected Dec 2019 related to likely exposure in wet market in Wuhan, Hubei, China, and declared a pandemic in 2020
Secondary household attack rate of 12-17%

Incubation period 4 to 5 days (range 2 to 11 days), possibly as long as 14 days in some cases
Main presenting symptoms were fever and cough, followed by myalgia, fatigue, headache, dyspnea
Other symptoms include dyspnea, rhinorrhea, vomiting, diarrhea, anosmia/hyposmia
Lymphopenia is common, as is hypoalbuminemia, elevated D-dimer, CRP, LDH, AST/ALT
Viral load detectable before symptom onset and peaks around the time of symptom onset

Please refer to a living systematic review on the topic
Slightly less reported fever and myalgias
Slightly more ICU admissions and mechanical ventilation
- Risk factors included age, obesity, hypertension, and diabetes
With regards to the fetus, there were more preterm deliveries (6%) and more needed NICU admission (25%)

PCR from NP swab
- Highest sensitivity within 5 days of symptom onset, with decreasing sensitivity as the disease enters the immune-mediated phase
- May be positive long after no longer infectious
Diagnostic accuracy of PCR by sample site (below) has a lot of heterogeneity among the studies

	Sensitivity	Specificity
Upper Respiratory Samples
Oral	56	99
Nasal	76	100
NP	97	100
Nasal	95	100
Saliva	85	100
Mid-turbinate	100	100
Upper Versus Lower Tract
Upper respiratory tract	57	100
Lower respiratory tract	81	100
Single Versus Repeat Testing
Single test	71	100
Repeat testing	100	100

Serology (IgM and IgG)
- Total antibodies have poor sensitivity (51%) in first week, and increases to about 90% by week 3

For patients no requiring supplemental oxygen, the focus is on supportive care
For patients requiring supplemental oxygen or with oxygen saturation less than 94%:
- Dexamethasone 6 mg PO/IV daily for 10 days, which has a mortality benefit
- Remdesivir 200 mg PO once on day one followed by 100 mg PO daily for 5-10 days, which has not been shown to have a mortality benefit
Avoid hydroxychloroquine/chloroquine, lopinavir-ritonavir
Other investigational therapeutics include tocilizumab

Awaiting results
- If symptomatic, HCWs should be off work
- If asymptomatic, HCWs may return to work while awaiting results, depending on the reason for testing and the staffing needs
Positive but asymptomatic: in exceptional circumstances, may return to work early

Non-test based (preferred)
- Asymptomatic: isolate for 10 days from swab
- Mild to moderate symptoms in immunocompetent person: 10 days from onset of symptoms, as long as afebrile and clinically improving
- Severe (i.e. ICU-level care) or immunocompromised: 20 days from onset of symptoms, as long as afebrile and clinically improving
  - Immunocompromise includes chemotherapy, untreated HIV with CD4 <200, primary immunodeficiency, prednisone 20 mg/day for 14 days, and other immunosuppressing medication
Test based (alternative): 2 negative swabs at least 24 hours apart (if still positive, repeat in 3 to 4 days), as long as afebrile and clinically improving

^ Louise Lansbury, Benjamin Lim, Vadsala Baskaran, Wei Shen Lim. Co-infections in people with COVID-19: a systematic review and meta-analysis. Journal of Infection. 2020;81(2):266-275. doi:10.1016/j.jinf.2020.05.046.
^ Scott Simpson, Fernando U. Kay, Suhny Abbara, Sanjeev Bhalla, Jonathan H. Chung, Michael Chung, Travis S. Henry, Jeffrey P. Kanne, Seth Kligerman, Jane P. Ko, Harold Litt. Radiological Society of North America Expert Consensus Document on Reporting Chest CT Findings Related to COVID-19: Endorsed by the Society of Thoracic Radiology, the American College of Radiology, and RSNA. Radiology: Cardiothoracic Imaging. 2020;2(2):e200152. doi:10.1148/ryct.2020200152.
^ Robert L. Gottlieb, Carlos E. Vaca, Roger Paredes, Jorge Mera, Brandon J. Webb, Gilberto Perez, Godson Oguchi, Pablo Ryan, Bibi U. Nielsen, Michael Brown, Ausberto Hidalgo, Yessica Sachdeva, Shilpi Mittal, Olayemi Osiyemi, Jacek Skarbinski, Kavita Juneja, Robert H. Hyland, Anu Osinusi, Shuguang Chen, Gregory Camus, Mazin Abdelghany, Santosh Davies, Nicole Behenna-Renton, Frank Duff, Francisco M. Marty, Morgan J. Katz, Adit A. Ginde, Samuel M. Brown, Joshua T. Schiffer, Joshua A. Hill. Early Remdesivir to Prevent Progression to Severe Covid-19 in Outpatients. New England Journal of Medicine. 2021. doi:10.1056/nejmoa2116846.