Coronavirus (COVID-19) / SARS-CoV-2 Infection - Clinical Overview
Updated: 2026-05-02 | Core sources: Pocket Medicine 9th Ed. p.439-440, CDC 2026, IDSA 2025, Taiwan CDC 2025, PubMed RCTs/reviews
Clinical Frame
COVID-19 的治療邏輯可以濃縮成一句話：早期高風險病人用 antiviral；需要氧氣的肺部發炎期用 corticosteroid，快速惡化或 critical illness 才加 immunomodulator。
這個框架比單純記藥名重要。Paxlovid、remdesivir、molnupiravir 主要處理 viral replication；dexamethasone、tocilizumab、baricitinib 則處理 host inflammatory lung injury。把藥放錯階段，可能沒效甚至有害，例如 non-hypoxic outpatient reflex 給 dexamethasone。
臨床每次遇到 COVID positive patient，先問：
- 發病第幾天？
- 是否 high-risk for progression？
- 是否因 COVID 需要 oxygen？
- Paxlovid 有無重大 drug-drug interaction 或 renal/hepatic dosing issue？
- 病程是否符合 COVID，還是同時有 PE、HF、bacterial pneumonia 或 ACS？
Microbiology and Epidemiology
SARS-CoV-2 是 enveloped positive-sense RNA coronavirus，主要經 respiratory particles 傳播。Asymptomatic 與 presymptomatic transmission 都可發生。Pocket Medicine 記載 incubation 可至 14 天，中位數約 4-5 天；Omicron-era 常更短，但臨床仍以暴露史、症狀開始時間與檢測結果綜合判斷。
疫苗與先前感染主要降低 severe disease、hospitalization 與 death，而不是完全阻止感染。Reinfection 可見，尤其在免疫逃脫變異株與免疫力下降後。
Risk Stratification
最需要早期 antiviral 的，是 mild-to-moderate COVID 但有進展為重症風險的人。年齡是最強 risk factor；多個共病會疊加風險。未接種或未更新疫苗、免疫低下、長照機構住民、CKD/ESRD、慢性心肺病、糖尿病、肥胖、cirrhosis 與 pregnancy 都會提高風險。
| Risk domain | Examples |
|---|---|
| Age/frailty | >=65, especially >=75; nursing home; frailty |
| Cardiometabolic | CAD, CHF, diabetes, severe obesity |
| Pulmonary | COPD, ILD, chronic respiratory failure, pulmonary hypertension |
| Kidney/liver | CKD, ESRD/hemodialysis, cirrhosis |
| Immunocompromised | Transplant, chemotherapy, anti-CD20, high-dose steroids, advanced HIV |
| Pregnancy | Pregnancy or early postpartum |
Clinical Presentation
COVID-19 可從 asymptomatic infection 到 critical illness。常見症狀包括 fever/chills、cough、sore throat、rhinorrhea、dyspnea、fatigue、myalgia、headache、nausea/vomiting、diarrhea；anosmia/dysgeusia 在早期 strains 較典型，現在敏感度較低。
老年人可能以 delirium、跌倒、食慾下降或 functional decline 表現。重症可出現 viral pneumonia、ARDS、PE/VTE、myocarditis/pericarditis、AKI、secondary bacterial pneumonia 或 multiorgan failure。
Diagnosis
NAAT/RT-PCR sensitivity 較高，適合高風險病人、住院病人或陰性 antigen 但臨床高度懷疑者。Rapid antigen test 速度快，陽性通常有幫助；但早期疾病或低病毒量可能 false negative，需要 repeat 或 PCR。
住院病人應依嚴重度做 CBC、CMP、renal/liver function、CXR，必要時 ABG/VBG。若有胸痛、明顯 tachycardia、hypoxemia 不成比例、D-dimer 高且臨床懷疑，應評估 PE，而不是把所有呼吸惡化都歸因於 COVID pneumonia。若有 focal consolidation、purulent sputum、sepsis 或二段式惡化，應評估 bacterial coinfection。
| Test / workup | Best use |
|---|---|
| NAAT / RT-PCR | High-risk treatment decision, hospitalized patient, antigen-negative but high suspicion |
| Rapid antigen | Fast confirmation; repeat if negative but suspicion persists |
| Multiplex respiratory PCR | Flu/RSV/COVID differentiation during respiratory virus season |
| CXR / CT | Hypoxemia, dyspnea, diagnostic uncertainty; CT especially for PE/alternative diagnosis |
| Cultures / procalcitonin | Severe disease or bacterial coinfection concern; interpret clinically |
Outpatient Treatment
Outpatient treatment 的重點是不要錯過時間窗。CDC 2026 強調，對有 severe COVID risk 的 mild/moderate patients，antiviral 應盡早開始，依藥物不同通常在 symptom onset 後 5-7 天內。
Paxlovid 是多數高風險 outpatient 的首選，但前提是 drug-drug interaction、renal dosing 與 hepatic contraindication 處理得好。Remdesivir 三天 IV 療程是 Paxlovid 不適合時的重要替代。Molnupiravir 效果較弱，通常是 Paxlovid/remdesivir 都不可用時的替代；pregnancy 應避免。
| Drug | Window | Role | Main cautions |
|---|---|---|---|
| Nirmatrelvir/ritonavir (Paxlovid) | ⇐5 days | Preferred oral antiviral for high-risk outpatient | CYP3A DDI, renal dosing, severe hepatic disease |
| Remdesivir | ⇐7 days | Alternative when Paxlovid unsuitable; strong outpatient RCT data | IV logistics, LFT/PT check |
| Molnupiravir | ⇐5 days | Last-line oral alternative | Lower efficacy, avoid pregnancy |
Paxlovid 開立前一定要檢查 medication list。高風險交互作用包括 antiarrhythmics、DOACs/warfarin、clopidogrel/ticagrelor、statins、tacrolimus/cyclosporine/sirolimus、carbamazepine/phenytoin/rifampin 等。對 transplant patient，Paxlovid 與 calcineurin inhibitors 的交互作用可以非常危險，應請 ID/transplant pharmacist 共同處理。
Taiwan Paxlovid Renal Update
台灣 CDC 2025-05-21 通函指出，Paxlovid 本地仿單已增列 eGFR <30 mL/min（含 hemodialysis）用法。建議療程 5 天：第 1 天 nirmatrelvir 300 mg + ritonavir 100 mg once；第 2-5 天 nirmatrelvir 150 mg + ritonavir 100 mg once daily；透析日於透析後給藥。
這是台灣實務重要差異：不能再用舊印象把所有 eGFR <30 的 COVID 高風險病人直接排除 Paxlovid。實際開立仍要依最新版仿單、院內 protocol 與藥師 DDI/renal dosing 核對。
Inpatient Treatment
住院治療要先分清楚「因 COVID 住院」還是「住院時剛好 COVID positive」。如果沒有因 COVID 需要 oxygen，通常不給 dexamethasone；若仍在早期且 high-risk，可以依 outpatient antiviral 邏輯評估。
需要 oxygen 的 COVID pneumonia，dexamethasone 6 mg daily up to 10 days 是核心。Remdesivir 對較早期、需要低流量氧氣的 hospitalized patient 較有角色；到 late critical illness 時 antiviral benefit 通常較小，需個別判斷。
若病人 oxygen requirement 快速上升、需要 HFNC/NIV，或已進入 mechanical ventilation/ECMO，應在 systemic corticosteroid 基礎上評估 additional immunomodulator。IDSA 2025 update 指出，在已決定要加一個 immunomodulator 的 severe/critical COVID adult，baricitinib 或 tocilizumab 都是合理選項，選擇取決於禁忌症、感染風險、肝腎功能、血球數與可近性。
| Clinical state | Treatment logic |
|---|---|
| No oxygen for COVID | No routine dexamethasone; consider antiviral only if early/high-risk |
| Low-flow oxygen | Dexamethasone; consider remdesivir, especially early disease |
| Rapidly increasing O2 / HFNC / NIV | Dexamethasone + consider baricitinib or tocilizumab |
| Mechanical ventilation / ECMO | ICU ARDS care + dexamethasone; immunomodulator if criteria fit |
| Bacterial coinfection/sepsis concern | Cultures and antibiotics as indicated; be cautious with immunomodulators |
不建議 routine 使用 hydroxychloroquine、ivermectin、lopinavir/ritonavir、或 non-evidence supplements。Antibiotics 也不應因 COVID positive 自動使用；只有 bacterial coinfection、sepsis 或 CAP/HAP indication 時才給。
Evidence Behind Major Treatments
這裡保留核心 trial/review，重點是幫助臨床理解「哪個族群有 benefit」。
| Intervention | Key evidence | Clinical meaning |
|---|---|---|
| Paxlovid | EPIC-HR, NEJM 2022 | High-risk unvaccinated outpatients early treatment markedly reduced hospitalization/death |
| Paxlovid in immune-era populations | Omicron-era observational cohorts; 2024 lower-risk/vaccinated data | Benefit concentrated in older/high-risk patients |
| Outpatient remdesivir | PINETREE, NEJM 2022 | 3-day IV course reduced progression in high-risk outpatients |
| Inpatient remdesivir | ACTT-1, NEJM 2020 | Shortened recovery in hospitalized lower respiratory COVID |
| Dexamethasone | RECOVERY, NEJM 2021 | Mortality benefit in oxygen/MV patients; no benefit without oxygen |
| IL-6 inhibitors | RECOVERY / REMAP-CAP | Benefit in selected severe/critical inflammatory COVID on steroids |
| JAK inhibitors | COV-BARRIER and related trials | Baricitinib useful in selected hospitalized severe COVID |
Anticoagulation and Complications
COVID-19 increases thrombotic risk, so hospitalized patients should at least receive VTE prophylaxis unless contraindicated. Therapeutic anticoagulation is for confirmed or strongly suspected VTE, or selected protocol-defined hospitalized patients; D-dimer elevation alone is not PE diagnosis.
臨床惡化時要重新打開 differential。COVID patient 若 hypoxemia 不成比例、胸痛、突然 tachycardia 或 hemoptysis，要想 PE。若有 orthopnea、edema、BNP 上升或 pulmonary edema pattern，要想 HF。若有 lobar consolidation、膿痰或 sepsis，要想 bacterial pneumonia。
Prevention and Infection Control
社區中有 COVID 或呼吸道病毒症狀時，應待症狀改善且退燒後再恢復活動，並在之後一段時間加強口罩、手衛生、通風與避免接觸高風險者。住院隔離與 aerosol-generating procedures 依院內 policy。
CDC 2025-2026 COVID vaccine guidance 採 individual-based/shared decision-making，但風險效益最明確的是 >=65 歲、免疫低下或有 severe COVID risk 的族群。台灣疫苗政策與可用產品需依當年度 Taiwan CDC 公告。
Special Populations
CKD/ESRD 病人現在在台灣不應自動排除 Paxlovid，但要用本地仿單減量並檢查交互作用。Transplant patient 最大問題常是 Paxlovid 與 tacrolimus/cyclosporine/sirolimus 的交互作用。Pregnancy 本身是 severe COVID risk；若符合適應症，不應只因懷孕就延誤有效治療，但 molnupiravir 應避免。
免疫低下，尤其 B-cell depleted 或 transplant patient，可能有 prolonged viral replication、rebound 或 persistent infection，這時應及早請 ID 評估是否需要延長或特殊 antiviral strategy。
Clinical Pearls
- Antiviral 是 early disease 藥；dexamethasone 是 hypoxic inflammatory lung disease 藥。
- No oxygen requirement 就不要 reflex 給 dexamethasone。
- Paxlovid 的難點是 DDI，不是只記劑量。
- eGFR <30 在台灣已有 Paxlovid 減量用法，需用新版仿單思考。
- COVID positive 不排除 PE、HF、ACS 或 bacterial pneumonia。
- Oxygen requirement 快速上升時，要想到 immunomodulator timing，而不是只加抗生素。
Recommended Reading
| Type | Citation | Key point |
|---|---|---|
| Textbook | Pocket Medicine 9th Ed. p.439-440 | COVID diagnosis and severity-based treatment skeleton |
| Guideline | CDC COVID outpatient treatment | Current outpatient antiviral options and timing |
| Guideline | CDC COVID clinical course/management | Severity-based management framework |
| Guideline | IDSA COVID-19 Treatment and Management | Antiviral, glucocorticoid, IL-6/JAK recommendations |
| Trial | EPIC-HR: Oral nirmatrelvir for high-risk outpatients. NEJM 2022 | Early Paxlovid reduces hospitalization/death in high-risk outpatient COVID |
| Trial | PINETREE: Outpatient remdesivir. NEJM 2022 | 3-day remdesivir prevents progression in high-risk outpatients |
| Trial | ACTT-1: Remdesivir final report. NEJM 2020 | Shorter recovery in hospitalized lower respiratory COVID |
| Trial | RECOVERY dexamethasone. NEJM 2021 | Mortality benefit in oxygen/MV, not no-oxygen |
| Guideline update | IDSA 2025 baricitinib vs tocilizumab update | Either baricitinib or tocilizumab for selected rapidly progressive severe/critical disease |
| Taiwan CDC | Paxlovid eGFR <30 mL/min 用法更新 | Taiwan local renal dosing update |