Compare conditions

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

Influenza

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In one line

·Flu is a virus that attacks the wet lining inside your nose, throat, and lungs, causing sudden fever, body aches, and cough — and high-risk people can get pneumonia fast.

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Normal physiology

·The wet lining inside your nose, throat, and breathing tubes (the respiratory epithelium) traps germs in sticky mucus, and tiny waving hairs called cilia sweep that mucus up and out before viruses can multiply.

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What goes wrong

·Influenza A or B virus breaks through the mucus trap and punches into the cells of the wet airway lining, hijacking each cell to make thousands of copies, then bursting it open and spreading to neighbors — that upstream break triggers all the fever, aches, cough, and risk of pneumonia you see downstream.

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Hallmark signs

·Sudden high fever (usually 100–104°F)
·Dry cough
·Muscle and body aches (myalgia)
·Severe fatigue and weakness
·Headache
·Chills and sweats
·Sore throat
·Stuffy or runny nose

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Red flags · escalate now

·Trouble breathing, fast breathing, or chest pain when breathing
·Confusion, severe drowsiness, or trouble waking up
·Symptoms improve for a day or two, then suddenly get worse with new high fever or cough (may signal bacterial pneumonia on top of flu)
·Severe weakness or dizziness that makes it hard to stand
·In children: bluish lips or face, not drinking enough fluids, or being so irritable they don't want to be held

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Workup

·Rapid influenza diagnostic test (RIDT) — nasal or throat swab
·RT-PCR (reverse transcription polymerase chain reaction) for influenza A and B — nasal swab
·Chest X-ray (posteroanterior and lateral views)
·Pulse oximetry (oxygen saturation, SpO₂)
·Complete blood count (CBC) with differential
·Blood culture (two sets from separate sites) if pneumonia or sepsis is suspected

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Treatment

·Oseltamivir 75 mg by mouth twice daily for 5 days (or baloxavir 40–80 mg single dose, or zanamivir 10 mg inhaled twice daily for 5 days)
·Isolation at home for at least 5 days from symptom onset AND until fever is gone for 24 hours without medicine; wear a mask around others
·Antibiotics (amoxicillin-clavulanate 875/125 mg twice daily, or ceftriaxone 1–2 g IV daily, or levofloxacin 750 mg daily) if secondary bacterial pneumonia develops
·Acetaminophen 650–1,000 mg every 6 hours or ibuprofen 400–600 mg every 6 hours, plus encourage oral fluids (water, broth, electrolyte drinks)
·Annual influenza vaccination (inactivated injectable vaccine or live-attenuated nasal spray, given in fall before flu season)
·Supplemental oxygen (nasal cannula or face mask) if SpO₂ < 90%, titrate to keep SpO₂ ≥ 90–92%
·IV fluids (normal saline or lactated Ringer's) if the patient is dehydrated or cannot drink

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NCLEX trap

·Influenza is caused by a virus, not bacteria. Antibiotics kill bacteria — they do nothing to viruses. Give antibiotics ONLY if a bacterial infection (like pneumonia) shows up later, usually 1–2 weeks after flu starts. The right move for flu itself is an antiviral medicine (oseltamivir or baloxavir) started within 48 hours of symptom start, especially for anyone at high risk (pregnant women, babies, elderly, people with weak immune systems, or chronic diseases like asthma, diabetes, or heart disease).
·The common cold also causes cough, runny nose, and sore throat. But influenza is different: it hits suddenly with high fever (often 102–104°F), severe muscle aches all over the body, extreme tiredness, and headache. A cold comes on slowly over a day or two and rarely causes bad body aches or high fever. To know for sure, use a rapid flu test (checks for flu virus proteins in nose or throat) or PCR (looks for flu virus genes) — both confirm influenza within minutes to hours.
·Yes, most healthy adults recover from flu in 1–2 weeks without medicine. But high-risk patients (pregnant women, infants, people over 65, anyone with a weak immune system, or anyone with chronic lung, heart, kidney, or liver disease) can develop pneumonia, respiratory failure, or even die. For them, start antiviral medicine (oseltamivir 75 mg twice a day for 5 days, or baloxavir 40 mg once) within the first 48 hours of symptoms. Do not wait — early treatment cuts the illness short and prevents dangerous complications.
·The cough is the body's way of clearing virus, dead cells, and mucus out of the airways. Stopping the cough traps that junk inside and can make infection worse. Instead, keep the patient hydrated (water, warm tea, soup) to loosen mucus, give acetaminophen or ibuprofen to bring down fever and ease body aches, and let the cough do its job. The cough will fade on its own as the airways heal.
·The flu vaccine only protects for one season. Influenza viruses change every year — scientists pick new vaccine strains each fall to match the viruses expected that winter. Even if you got vaccinated last year, you need a new shot this year. Also, the vaccine does not guarantee you will not catch flu, but if you do get sick, the illness is usually milder and you are far less likely to develop pneumonia or need the hospital.
·Influenza fever comes in waves — it can drop for a few hours, then spike again. A patient with only mild fever at this moment can get very sick hours or days later, especially if they are high-risk. Always check risk factors (age, pregnancy, chronic illness, weak immune system). Start antiviral medicine if they qualify. Also watch for danger signs: trouble breathing, chest pain, confusion, or dizziness — these mean the lungs are failing or pneumonia is setting in, and the patient needs urgent care, not home rest.

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