Clinical Pearl Series:Special Viral Infection by Coronaviruses

--From [Yale-G First Aid: Crush USMLE Step 2CK and Step 3] By Dr. Yale Gong, USMLE-Certified, Sr. Advisor of www.medicine.net

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Coronaviruses are important human and animal pathogens, accounting for 5-10% community-acquired URIs in adults and probably also playing a role in severe LRIs, particularly in immune-compromised patients and primarily in the winter. 

Virology: Coronaviruses are medium-sized enveloped positive-stranded RNA viruses as a family within the Nidovirales order, further classified into four genera (), encoding 4-5 structural proteins, S, M, N, HE, and E; severe types: severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and novel coronavirus [2019-nCoV or SARS-CoV-2, a beta variant, which causes Coronavirus Disease 2019 (COVID-19)].

Routes of transmission: Similar to that of rhinoviruses, via direct contact with infected secretions or large aerosol droplets. Immunity develops soon after infection but wanes gradually over time. Reinfection is common.

Clinical manifestations and diagnosis: 1. Coronaviruses mostly cause respiratory symptoms (nasal congestion, rhinorrhea, sore throat, and cough) and influenza-like symptoms (fever, headache). 2. Severe types (MERS-CoV, SARS-CoV and SARS-CoV-2): Typically with pneumonia--fever, cough, dyspnea, and bilateral infiltrates on chest imaging, +/- enterocolitis (diarrhea), particularly in immunocompromised hosts (HIV+, elders, children). 3. COVID-19 delta omicron variant appears to be more contagious but associated with milder illness similar to URI, accounting for around 80% of cases. Post-COVID-19 prolonged disorders were reported. 4. Most community-acquired COVID-19 infections are diagnosed by a viral antigen test or nucleic acid amplification test (NAAT, RT-PCR, more sensitive and specific) using nasopharyngeal swab specimen.

Treatment: 1. It mainly consists of ensuring appropriate control of infection and symptoms and supportive care for sepsis and acute respiratory distress syndrome (oxygen, IMV, etc.). 2. Clinical trials: Some studies showed that chloroquine may have activity against the SARS-CoV, HCoV-229E, and HCoV-OC43, and remdesivir against COVID-19. Dexamethasone may have clinical benefit in severe cases. No effective treatment for COVID-19 has been confirmed so far.

Prevention: 1. For most coronaviruses: The same as for rhinovirus infections, which consist of handwashing and the careful disposal of materials infected with nasal secretions. 2. For novel coronavirus, MERS-CoV, and SARS-CoV: (1) Preventing exposure by diligent hand washing, respiratory hygiene, and avoiding close contact with live or dead animals and ill individuals. (2) Infection control for suspected or confirmed cases: Wear a medical mask to contain their respiratory secretions and seek medical attention; standard contact and airborne precautions, with eye protection. (3) New promising vaccines for COVID-19, including mRNA based and viral vector vaccines, are recommended for most adults without special conditions or risk factors. While the vaccination has yielded decreased morbidities and mortalities, be alert for some rare complications such as vaccine-induced thrombotic thrombocytopenia and myocarditis, etc. in patients with risk factors, and increased resistance to the Delta Omicron variant.