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href="/topics/en-us/3000168/treatment-algorithm" id="Treatment algorithm">Treatment algorithm</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Emerging link" href="/topics/en-us/3000168/emergingtxs" id="Emerging">Emerging</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Prevention link" href="/topics/en-us/3000168/prevention" id="Prevention">Prevention</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Patient discussions link" href="/topics/en-us/3000168/patient-discussions" id="Patient discussions">Patient discussions</a></li></ul></li><li><a href="#" class="parent"><span>Follow up</span><span class="material-icons"></span><span class="material-icons"></span></a><ul role="menu" id="menu-4" data-test="menu-4"><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Monitoring link" href="/topics/en-us/3000168/monitoring" id="Monitoring">Monitoring</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Complications link" href="/topics/en-us/3000168/complications" id="Complications">Complications</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Prognosis link" href="/topics/en-us/3000168/prognosis" id="Prognosis">Prognosis</a></li></ul></li><li><a href="#" class="parent"><span>Resources</span><span class="material-icons"></span><span class="material-icons"></span></a><ul role="menu" id="menu-5" data-test="menu-5"><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Guidelines link" href="/topics/en-us/3000168/guidelines" id="Guidelines">Guidelines</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Images and videos link" href="/topics/en-us/3000168/images-and-videos" id="Images and videos">Images and videos</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="References link" href="/topics/en-us/3000168/references" class="js-menu-references" id="References">References</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Patient information link" href="/topics/en-us/3000168/patient-leaflets" id="Patient information">Patient information</a></li><li class="menus-no-link" role="none"><a role="menuitem" aria-label="Evidence link" href="/topics/en-us/3000168/evidence" id="Evidence">Evidence</a></li></ul></li></ul></nav></div><div class="d-flex align-items-center justify-content-center clear-both py-2 bg-light-4 border-top-light-gray"><a class="fullDetails-locked d-flex align-items-center justify-content-center" href="/log-in"><img src="/images/padlock-open.svg" class="mr-2" alt="padlock-open"><span>This topic is available for free</span></a></div></div><div class="row"><div class="col-md-8"><div id="dates"><div class="row allUpdates"><div class="col-md-4"><span data-test="topic-last-reviewed">Last reviewed: </span><span data-test="topic-last-reviewed-date">22 Jan 2025</span></div><div class="col-md-4"><span data-test="topic-last-updated">Last updated: </span><span data-test="topic-last-updated-date">24 Oct 2024</span></div><div class="col-md-4"></div></div><div class="updatesContent"><div class="collapse" id="impUpdate"><div class="card arrow-card acRight"><div class="card-block"><span class="icon icon-bp-icons-close close" data-test="imp-update-close"></span></div></div></div></div></div><div class="d-flex"><h2 id="sr-only" class="gpw-free">Summary</h2></div><div class="card mb-4"><div class="card-block"><div class="expandable" data-test="topic-summary-expandable"><p class="w-75">Respiratory transmission is the dominant mode of transmission, with proximity and ventilation being the key determinants of transmission risk. Transmission is more likely if contacts are exposed shortly before or after symptom onset in the index patient.</p><p class="w-75">Patients may be minimally symptomatic or asymptomatic, while others may present with severe pneumonia or other complications.</p><p class="w-75">People with comorbidities are at increased risk for severe disease, and the more comorbidities, the greater the risk. Hypertension, obesity, and diabetes are the most prevalent comorbidities.</p><p class="w-75">Diagnosis is confirmed with real-time reverse transcription polymerase chain reaction (RT-PCR); rapid antigen tests may be recommended in certain circumstances.</p><p class="w-75">Management depends on disease severity and focuses on infection prevention and control measures, symptom management, prevention of disease progression (e.g., antiviral treatment), optimized supportive care, and organ support in severe or critical illness.</p><p class="w-75">Numerous vaccines are available globally for prevention.</p></div><h3 class="pl-0" data-test="topic-summary-def">Definition</h3><div class="expandable" data-test="topic-summary-content"><p class="w-75">A potentially severe acute respiratory infection caused by the novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).<span class="reference"><a href="#referencePop1" data-trigger="click focus" role="button" data-animation="false" data-toggle="popover" class="referencePop" aria-label="Open reference: 1">[1]</a><span class="citationText" aria-hidden="true">Coronaviridae Study Group of the International Committee on Taxonomy of Viruses. The species severe acute respiratory syndrome-related coronavirus: classifying 2019-nCoV and naming it SARS-CoV-2. Nat Microbiol. 2020 Apr;5(4):536-44.</span><span class="citationFullTextUrl" aria-hidden="true"> https://www.nature.com/articles/s41564-020-0695-z </span><span class="referenceUniqueId" aria-hidden="true"> http://www.ncbi.nlm.nih.gov/pubmed/32123347?tool=bestpractice.com </span></span> The clinical presentation is generally that of a respiratory infection with a symptom severity ranging from a mild common cold-like illness, to a severe viral pneumonia leading to acute respiratory distress syndrome that is potentially fatal. Complications of severe disease include, but are not limited to, multi-organ failure, septic shock, and venous thromboembolism. Symptoms may be persistent and continue for more than 12 weeks in some patients.</p><p class="w-75">Several variants of SARS-CoV-2 have been identified. The majority of SARS-CoV-2 variants are now extinct, with the current circulating variant of concern being the Omicron variant (and its subvariants). Variants have sequentially replaced each other since the start of the pandemic, with the most successful variants being Alpha, Delta, and Omicron. Alpha and Delta emerged in late 2020, with Omicron emerging in late 2021. Omicron subvariants are currently circulating.</p></div></div></div><h3>History and exam</h3><div id="histEx" class="card-group mt-3 no-shadow"><div class="card"><div class="card-block"><h4 class="card-title mb-3"><a href="/topics/en-us/3000168/history-exam#keyFactors">Key diagnostic factors</a></h4><ul id="diagFactors" class="list-aligned mb-1" data-test="diag-factors"><li>fever</li><li>cough</li><li>dyspnea</li><li>altered sense of smell/taste</li></ul><div class="fullDetails mt-2" data-test="full-details-diag-factors"><a href="/topics/en-us/3000168/history-exam#keyFactors">Full details</a></div></div></div><div class="card"><div class="card-block"><h4 class="card-title mb-3"><a href="/topics/en-us/3000168/history-exam#otherFactors">Other diagnostic factors</a></h4><ul id="otherFactors" class="list-aligned mb-1"><li>fatigue</li><li>myalgia or arthralgia</li><li>sore throat</li><li>headache</li><li>rhinorrhea or nasal congestion</li><li>sneezing</li><li>expectoration</li><li>chest pain/tightness</li><li>malaise</li><li>dizziness</li><li>confusion or delirium</li><li>gastrointestinal symptoms</li><li>cutaneous symptoms</li><li>ocular symptoms</li><li>signs of pneumonia or acute respiratory distress</li><li>hemoptysis</li><li>audio-vestibular symptoms</li><li>oral mucosal lesions</li></ul><div class="fullDetails mt-2" data-test="full-details-other-factors"><a href="/topics/en-us/3000168/history-exam#otherFactors">Full details</a></div></div></div><div class="card"><div class="card-block"><h4 class="card-title mb-3"><a href="/topics/en-us/3000168/history-exam#riskFactors">Risk factors</a></h4><ul id="riskFactors" class="list-aligned mb-1"><li>contact with probable or confirmed case</li><li>residence/work in location with high risk of transmission</li><li>older age</li><li>male sex</li><li>ethnicity</li><li>residence in a long-term care facility</li><li>presence of comorbidities</li><li>obesity</li><li>cardiovascular disease</li><li>diabetes</li><li>chronic respiratory disease</li><li>chronic kidney disease</li><li>chronic liver disease</li><li>pregnancy</li><li>smoking</li><li>malignancy</li><li>cerebrovascular disease</li><li>mental health disorders</li><li>solid organ or blood stem cell transplant</li><li>disabilities</li><li>dementia</li><li>immunosuppression</li><li>HIV infection</li><li>physical inactivity</li><li>hemoglobin disorders</li><li>hypertension</li><li>substance use disorders</li><li>children with certain underlying conditions</li><li>vitamin D deficiency</li><li>proton-pump inhibitor use</li><li>corticosteroid use</li><li>autoimmune disease</li><li>thyroid disease</li><li>Parkinson disease</li><li>gout</li><li>dyslipidemia</li><li>surgery</li><li>blood groups A and B</li><li>gut dysbiosis</li><li>environmental factors</li></ul><div class="fullDetails mt-2" data-test="full-details-risk-factors"><a href="/topics/en-us/3000168/history-exam#riskFactors">Full details</a></div></div></div></div><h3>Diagnostic tests</h3><div id="diagInvs" class="card-group mt-3 no-shadow"><div class="card"><div class="card-block"><h4 class="card-title mb-3"><a href="/topics/en-us/3000168/investigations#firstOrder">1st tests to order</a></h4><ul id="initialTests" class="list-aligned mb-1"><li>real-time reverse transcription polymerase chain reaction (RT-PCR)</li><li>rapid antigen test</li><li>pulse oximetry</li><li>ABG</li><li>CBC</li><li>comprehensive metabolic panel</li><li>blood glucose level</li><li>coagulation screen</li><li>cardiac biomarkers</li><li>serum C-reactive protein</li><li>serum erythrocyte sedimentation rate</li><li>serum lactate dehydrogenase</li><li>serum procalcitonin</li><li>serum ferritin level</li><li>blood and sputum cultures</li><li>chest x-ray</li></ul><div class="fullDetails mt-2"><a href="/topics/en-us/3000168/investigations#firstOrder">Full details</a></div></div></div><div class="card"><div class="card-block"><h4 class="card-title mb-3"><a href="/topics/en-us/3000168/investigations#toConsider">Tests to consider</a></h4><ul id="subTests" class="list-aligned mb-1"><li>computed tomography (CT) chest</li><li>lung ultrasound</li><li>serology</li></ul><div class="fullDetails mt-2"><a href="/topics/en-us/3000168/investigations#toConsider">Full details</a></div></div></div></div><h3 class="d-flex align-items-center">Treatment algorithm</h3><div class="card-group mt-3 mb-4 treatment-table topic-page no-shadow" data-test="treatment-table"><div class="card"><div class="card-block p-0"><div class="rowHead" id="acute"><div>ACUTE</div></div><div class="panel-heading bg-white"><h3 class="tx-content"><a href="/topics/en-us/3000168/treatment-algorithm#">mild to moderate (nonsevere) disease</a></h3></div><div class="panel-heading bg-white"><h3 class="tx-content"><a href="/topics/en-us/3000168/treatment-algorithm#">severe disease</a></h3></div><div class="panel-heading bg-white"><h3 class="tx-content"><a href="/topics/en-us/3000168/treatment-algorithm#">critical disease</a></h3></div></div></div></div><div data-details="wrapper" class="mb-3"><div class="d-flex justify-content-between"><h3 class="text-grey-light" data-test="topic-summary-contributors">Contributors</h3><button role="button" class="d-none d-sm-block p-0 text-dark-blue bg-transparent" data-details="collapsed"><span data-details="text">VIEW ALL</span><span class="sr-only">Authors</span><span class="material-icons" aria-hidden="true"></span></button></div><div class="card py-2 px-3 bg-dark-blue"><div class="d-flex justify-content-between"><h4 class="text-white font-weight-bold font-s m-0 p-0 text-uppercase">Authors</h4></div></div><div class="card border-bottom-0"><details class="border-b-dark-blue"><summary class="d-flex align-items-center acc-panel-toggle acc-panel-heading contributors text-dark-blue"><h5 class="acc-panel-heading-text mb-0" >Jennifer M. Hendrick, MD</h5></summary><div class="js-acc-panel-body panel-body"><p class="w-75">Assistant Professor of Medicine</p><p class="w-75">University of Virginia Health System</p><p class="w-75">Division of Infectious Diseases and International Health</p><p class="w-75">Charlottesville</p><p class="w-75">VA</p><h6 class="font-weight-bold">Disclosures</h6><p>JMH declares that she has no competing interests.</p></div></details></div><div class="card border-bottom-0"><details class="border-b-dark-blue"><summary class="d-flex align-items-center acc-panel-toggle acc-panel-heading contributors text-dark-blue"><h5 class="acc-panel-heading-text mb-0" >Tom E. Fletcher, MBE, PhD, MBChB, MRCP, DTM&H</h5></summary><div class="js-acc-panel-body panel-body"><p class="w-75">Senior Clinical Lecturer and Defence Consultant in Infectious Diseases</p><p class="w-75">Royal Liverpool University Hospital and Liverpool School of Tropical Medicine</p><p class="w-75">Liverpool</p><p class="w-75">UK</p><h6 class="font-weight-bold">Disclosures</h6><p>TEF is a consultant/expert panel member to the World Health Organization, and is funded by the UK Surgeon General, the NHS, and Liverpool School of Tropical Medicine. TEF is partially supported by the National Institute of Health Research Health Protection Unit (NIHR HPRU) in Emerging and Zoonotic Infections at University of Liverpool in partnership with the UK Health Security Agency (UKHSA; formerly Public Health England) in collaboration with Liverpool School of Tropical Medicine. He is affiliated with Liverpool School of Tropical Medicine. He has received research grants from the Wellcome Trust, Medical Research Council, and the UK Public Health Rapid Support Team (UK-PHRST). The views expressed are those of the author and not necessarily those of the NHS, the NIHR, the Department of Health, or UKHSA.</p></div></details></div><div class="card border-bottom-0"><details class="border-b-dark-blue"><summary class="d-flex align-items-center acc-panel-toggle acc-panel-heading contributors text-dark-blue"><h5 class="acc-panel-heading-text mb-0" >Robert Fowler, MDCM, MS (Epi), FRCP(C)</h5></summary><div class="js-acc-panel-body panel-body"><p class="w-75">H. Barrie Fairley Professor of Critical Care</p><p class="w-75">University Health Network and Interdepartmental Division of Critical Care Medicine</p><p class="w-75">Director</p><p class="w-75">Clinical Epidemiology and Health Care Research</p><p class="w-75">Institute of Health Policy, Management and Evaluation</p><p class="w-75">Dalla Lana School of Public Health</p><p class="w-75">University of Toronto</p><p class="w-75">Chief</p><p class="w-75">Tory Trauma Program</p><p class="w-75">Sunnybrook Hospital</p><p class="w-75">Toronto</p><p class="w-75">Canada</p><h6 class="font-weight-bold">Disclosures</h6><p>RF declares that he has no competing interests.</p></div></details></div><div class="card border-bottom-0"><details class="border-b-dark-blue"><summary class="d-flex align-items-center acc-panel-toggle acc-panel-heading contributors text-dark-blue"><h5 class="acc-panel-heading-text mb-0" >Acknowledgements</h5></summary><div class="js-acc-panel-body panel-body"><p class="w-75">Dr Jennifer M. Hendrick, Dr Tom E. Fletcher, and Dr Robert Fowler would like to gratefully acknowledge Dr Nicholas J. Beeching, previous contributor to this topic.</p><h6 class="font-weight-bold">Disclosures</h6><p>NJB is partially supported by the National Institute of Health Research Health Protection Unit (NIHR HPRU) in Emerging and Zoonotic Infections at University of Liverpool in partnership with the UK Health Security Agency (UKHSA; formerly Public Health England), in collaboration with Liverpool School of Tropical Medicine. He is affiliated with Liverpool School of Tropical Medicine. The views expressed are those of the author and not necessarily those of the NHS, the NIHR, the Department of Health, or UKHSA.</p></div></details></div></div><div data-details="wrapper" class="mb-3"><div class="d-flex justify-content-end"><button role="button" class="d-none d-sm-block p-0 text-dark-blue bg-transparent" data-details="collapsed"><span data-details="text">VIEW ALL</span><span class="sr-only">Peer reviewers</span><span class="material-icons" aria-hidden="true"></span></button></div><div class="card py-2 px-3 bg-dark-blue"><div class="d-flex"><h4 class="text-white font-weight-bold font-s m-0 p-0 text-uppercase">Peer reviewers</h4></div></div><div class="card border-bottom-0"><details class="border-b-dark-blue"><summary class="d-flex align-items-center acc-panel-toggle acc-panel-heading contributors text-dark-blue"><h5 class="acc-panel-heading-text mb-0" >William A. Petri, Jr., MD, PhD</h5></summary><div class="js-acc-panel-body panel-body"><p class="w-75">Professor</p><p class="w-75">Division of Infectious Diseases and International Health</p><p class="w-75">University of Virginia</p><p class="w-75">Charlottesville</p><p class="w-75">VA</p><h6 class="font-weight-bold">Disclosures</h6><p>WAP declares that he has no competing interests.</p></div></details></div><div class="card border-bottom-0"><details class="border-b-dark-blue"><summary class="d-flex align-items-center acc-panel-toggle acc-panel-heading contributors text-dark-blue"><h5 class="acc-panel-heading-text mb-0" >Xin Zhang, MD, PhD</h5></summary><div class="js-acc-panel-body panel-body"><p class="w-75">Attending Physician</p><p class="w-75">The Fifth Medical Center of PLA General Hospital</p><p class="w-75">Clinical Division and Research Center of Infectious Disease</p><p class="w-75">Beijing</p><p class="w-75">China</p><h6 class="font-weight-bold">Disclosures</h6><p>XZ declares that he has no competing interests.</p></div></details></div><div class="card border-bottom-0"><details class="border-b-dark-blue"><summary class="d-flex align-items-center acc-panel-toggle acc-panel-heading contributors text-dark-blue"><h5 class="acc-panel-heading-text mb-0" >Ran Nir-Paz, MD</h5></summary><div class="js-acc-panel-body panel-body"><p class="w-75">Associate Professor in Medicine</p><p class="w-75">Department of Clinical Microbiology and Infectious Diseases</p><p class="w-75">Hadassah Hebrew University Medical Center</p><p class="w-75">Jerusalem</p><p class="w-75">Israel</p><h6 class="font-weight-bold">Disclosures</h6><p>RNP has received research grants from US-Israel Binational Science Foundation, Hebrew University, Rosetrees Trust, and SpeeDx. He is chair of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Mycoplasma and Chlamydia Infections (ESGMAC). RNP is a consultant for and has stocks in eDAS Healthcare. He is also chairperson of the Israeli Society for Infectious Diseases guidelines committee.</p></div></details></div></div></div><div class="col-md-4"><div class="serp_detail"><div id="rhs-card"><ul class="list-group list-group-flush" layout:fragment="content"><li class="list-group-item p-0 hasImage" id="rhsImage"><a href="/topics/en-us/3000168/images-and-videos" class="w-100"><img class="card-img-bottom w-100" src="/api/image/3000168/en-us/normal/3000168-1.jpg?status=ACTIVE" alt="Coronavirus disease 2019 (COVID-19) images"></a></li><li class="list-group-item" id="rhsDifferentialDiagnosis"><div><h4 class="card-title x-text-secondary"><a href="/topics/en-us/3000168/differentials">Differentials</a></h4><ul class="list list-rollback list-aligned pt-0"><li><a href="/topics/en-us/3000168/differentials#collapseDiff-ac3d6258-1933-404a-b61f-438073ac08a5">Community-acquired pneumonia</a></li><li><a href="/topics/en-us/3000168/differentials#collapseDiff-3fec4c85-8dc4-4562-b447-d4d626a6f240">Influenza infection</a></li><li><a href="/topics/en-us/3000168/differentials#collapseDiff-05e79abf-b5fb-4b37-971f-a3527052e2fa">Common cold</a></li></ul><a class="fdRHS" href="/topics/en-us/3000168/differentials">More Differentials</a></div></li><li class="list-group-item" id="rhsGuidelines"><div><h4 class="card-title x-text-secondary"><a href="/topics/en-us/3000168/guidelines">Guidelines</a></h4><ul class="list list-rollback list-aligned pt-0"><li><a href="https://www.idsociety.org/practice-guideline/alphabetical-guidelines">Infectious Diseases Society of America guidelines on the treatment and management of patients with COVID-19</a></li><li><a href="https://www.who.int/publications/i/item/WHO-2019-nCoV-clinical-2023.2">Clinical management of COVID-19: living guideline</a></li></ul><a class="fdRHS" href="/topics/en-us/3000168/guidelines">More Guidelines</a></div></li><li class="list-group-item" id="rhsPatientLeaflets"><div><h4 class="card-title x-text-secondary"><a href="/topics/en-us/3000168/patient-leaflets">Patient information</a></h4><p><a class="serpPL" data-patient-leaflet-title="Coronavirus (COVID-19): vaccines" href="/patient-leaflets/en-us/html/3000208/Coronavirus%20%28COVID-19%29%3A%20vaccines"><span class="icon icon-bp-icons-patient-leaflets" aria-hidden="true"></span><span>Coronavirus (COVID-19): vaccines </span></a></p><p><a class="serpPL" data-patient-leaflet-title="COVID-19 (coronavirus)" href="/patient-leaflets/en-us/html/3000166/COVID-19%20%28coronavirus%29"><span class="icon icon-bp-icons-patient-leaflets" aria-hidden="true"></span><span>COVID-19 (coronavirus) </span></a></p><a class="fdRHS" href="/topics/en-us/3000168/patient-leaflets">More Patient information</a></div></li><li class="list-group-item" id="rhsProceduralVideos"><h4 class="card-title x-text-secondary"><a 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