Compare conditions

Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

COVID-19

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In one line

·SARS-CoV-2 virus enters through ACE2 receptors in the airway and lungs, triggering immune swelling that ranges from mild cough to life-threatening lung failure.

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Normal physiology

·Your airways and lungs are lined with special cells that catch germs, make mucus to trap them, and sweep them out with tiny waving hairs (cilia). Deep in the lungs, millions of thin air sacs (alveoli) let oxygen jump from air into your blood and carbon dioxide (waste gas) jump out — like a screen door that only good air can pass through.

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What goes wrong

·The SARS-CoV-2 virus locks onto a doorway called ACE2 on airway and lung cells, slips inside, and makes thousands of copies. The infected cells die and burst, spilling virus onto neighbors. Your immune system charges in with white blood cells and chemicals (cytokines) that cause swelling and mucus in the airways — that is the cough and shortness of breath. If the virus spreads into the deep lung air sacs, immune swelling fills them with fluid (pneumonia), so oxygen cannot cross into your blood. In the sickest patients, the immune response goes too far (cytokine storm), the air sacs collapse, and clots form in lung blood vessels, choking off oxygen completely (ARDS — acute respiratory distress syndrome, meaning the lungs fail).

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Hallmark signs

·Fever
·Cough (usually dry)
·Loss of smell or taste
·Shortness of breath or fast breathing
·Fatigue (feeling very tired)
·Headache
·Belly pain, nausea, or diarrhea
·Low oxygen level (hypoxia) without feeling very short of breath (silent low oxygen (hypoxia))

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Red flags · escalate now

·Trouble breathing, chest pain, or blue lips or face (means oxygen is too low)
·Confusion or trouble waking up (means the brain is not getting enough oxygen)
·Sudden worsening around day 7 to 10 of illness (may signal severe lung inflammation or a clot forming)

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Workup

·SARS-CoV-2 PCR (nasal swab)
·SARS-CoV-2 rapid antigen test (nasal swab)
·Pulse oximetry (oxygen saturation, SpO₂)
·Chest X-ray
·C-reactive protein (CRP)
·D-dimer
·Complete blood count (CBC)
·Ferritin

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Treatment

·Nirmatrelvir-ritonavir (Paxlovid) started within 5 days of symptom onset for high-risk patients (age ≥65, diabetes, obesity, immunocompromised)
·Remdesivir (antiviral IV infusion) for hospitalized patients or high-risk outpatients within 7 days of symptoms
·Dexamethasone 6 mg once daily (oral or IV) for hospitalized patients requiring oxygen
·Baricitinib (JAK inhibitor) or tocilizumab (IL-6 blocker) for hospitalized patients with rising oxygen needs despite steroids
·Preventive (Prophylactic)-dose anticoagulation (blood thinner, usually low-molecular-weight heparin) for most hospitalized patients
·Supplemental oxygen (nasal cannula, high-flow nasal cannula, or non-invasive ventilation) to keep SpO₂ ≥92%
·Mechanical ventilation (intubation and ventilator) when oxygen levels stay below 90% despite maximum non-invasive support

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NCLEX trap

·COVID-19 can silently damage the deep parts of the lungs even when oxygen looks okay on the finger monitor. This is called 'quiet low oxygen (hypoxia)' — the lungs are failing but the person does not feel it yet. Always test with a nose swab or blood test even if oxygen seems fine. Do not trust symptoms alone to rule it out.
·Fever is actually the body's helper, not the enemy. In COVID-19, fever means inflammation is fighting the virus. The real target is helping the lungs breathe and giving antivirals like nirmatrelvir-ritonavir (Paxlovid) within 5 days of symptoms starting — not cooling the fever. Let the fever do its job unless it goes dangerously high or the patient feels miserable.
·COVID-19 is caused by a virus, not bacteria. Antibiotics do not kill viruses. Only give antibiotics if a second bacterial infection happens later (like if new fever and yellow or green mucus appear after the person seemed to be getting better). The real fix early on is antivirals and breathing support.
·COVID-19 reinfection happens because new variants (changed versions of the virus) can escape the body's memory from the first infection. Previous infection gives some protection but not complete immunity. Vaccines keep working better than relying on an old infection to protect you.
·COVID-19 can look mild on Day 2 or 3, then crash hard on Day 4 or 5. Watch high-risk patients closely (older adults, diabetes, lung disease, weak immune system). Give antivirals early within the first 5 days. Do not wait to see if they get worse — by then the window to stop severe disease has closed.
·In COVID-19, oxygen below 94% signals lung injury (the oxygen sacs in the lungs are filling with fluid and inflammation). This is the upstream break. Intervene now with oxygen support and monitor closely for rapid decline. 'Quiet low oxygen (hypoxia)' means the lungs can fail faster than you expect, even if the person looks calm.

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