Influenza

Pathophysiology

Influenza viruses: Type A (most virulent, responsible for pandemics, infects humans and animals), Type B (moderate severity, humans only), Type C (mild, rarely significant). Surface glycoproteins hemagglutinin (H) and neuraminidase (N) define subtypes (e.g., H1N1, H3N2) and are the targets of immune recognition.
Antigenic drift: Small, cumulative mutations in H and N genes occur continuously, producing new strains that partially evade existing immunity. This is why annual vaccination is needed.
Antigenic shift: Major reassortment of genetic material between human and animal influenza strains (typically in birds or pigs), creating a novel virus to which the human population has no prior immunity. This is the mechanism behind pandemics.
Tissue damage: Influenza viruses target mucus-secreting, ciliated epithelial cells in the respiratory tract, killing them. Cell death destroys the mucociliary escalator and creates epithelial gaps, exposing the underlying tissue to secondary bacterial invasion. This is why post-influenza bacterial pneumonia is a common and dangerous complication.
Systemic inflammatory response: The intensity of systemic symptoms (fever, myalgias, fatigue) reflects the magnitude of the cytokine response to viral infection. Influenza triggers a more robust inflammatory cascade than rhinoviruses, which explains why it feels so much worse than a cold despite both being "respiratory infections."

Abrupt onset — can progress from feeling well to severely ill within hours (in contrast to the cold's gradual onset over 1–2 days)
High fever (often > 102°F/38.9°C) lasting 3–5 days
Severe myalgias (muscle aches) and arthralgias (joint pain) — often described as "it hurts to move"
Debilitating fatigue and prostration — the client is bed-bound, unable to work or perform daily tasks
Headache, chills, and rigors (shaking chills)
Nonproductive (dry) cough, sore throat, and nasal congestion
Sudden worsening after initial improvement, or development of productive cough with colored/streaked sputum — suggests secondary bacterial pneumonia

Dyspnea, persistent chest pain, or cyanosis — suggests pneumonia or other pulmonary complication. Urgent medical referral
Sudden worsening after initial improvement (biphasic illness) — classic pattern of secondary bacterial superinfection. Medical referral
Confusion, persistent vomiting, or signs of dehydration — suggests severe systemic illness. Medical referral
Reye syndrome in children given aspirin during viral illness — encephalopathy and liver failure. Aspirin is contraindicated in children with influenza
High-risk populations (adults > 65, children < 5, immunocompromised, pregnant, chronic cardiopulmonary disease) have significantly higher complication and mortality rates

Acute phase: Strictly contraindicated. Massage during active influenza is harmful, not merely unhelpful. The immune system is maximally engaged, and massage increases metabolic demand while the body is already in a hypercatabolic state. Massage during early infection can make the client significantly sicker.
Contagion: Influenza is contagious starting 1 day before symptoms appear and for up to 7 days after onset (up to 3 weeks in immunocompromised individuals). Reschedule to protect the therapist and subsequent clients.
Recovery phase: Massage may be appropriate once fever has resolved for at least 24 hours, systemic symptoms have substantially improved, and the client feels well enough to tolerate treatment. Post-influenza fatigue can persist for 1–2 weeks after fever resolution.
Flu season screening: During flu season (October–April), screen clients presenting with unexplained muscle aches and headache for fever before proceeding with the session. A quick temperature check or verbal screening can prevent treating a client in the early contagious phase.
Post-influenza muscle recovery: The severe myalgias of influenza are cytokine-mediated inflammation, not musculoskeletal injury. They resolve with the infection. Massage during recovery can provide comfort but does not "treat" the myalgias.

Category A7 — Systemic Conditions (Respiratory)
Distinguish influenza from the common cold: abrupt onset, high fever (> 102°F), severe systemic symptoms, potential life-threatening complications — versus the cold's gradual onset, mild fever, and predominantly nasal symptoms
Antigenic shift (major, pandemic-causing) versus antigenic drift (minor, annual) — testable immunology concepts
Reye syndrome risk with aspirin use in children during viral illness — a classic pharmacology test point
Antivirals (oseltamivir/Tamiflu) are most effective within 48 hours of symptom onset — this is a time-sensitive referral point
The decision to reschedule during acute illness is a testable clinical judgment scenario

Influenza is distinguished from the common cold by abrupt onset, high fever, severe systemic symptoms, and potential life-threatening complications
Massage is strictly contraindicated during acute influenza — it increases metabolic demand on an already maximally stressed immune system and can worsen the illness
Contagious from 1 day before symptoms through 7 days after onset. Reschedule to protect the therapist and other clients
Secondary bacterial pneumonia (signaled by biphasic worsening after initial improvement) is the most dangerous complication
During flu season, screen clients with unexplained myalgias and headache for fever before proceeding
Recovery-phase massage is appropriate once fever has resolved for 24+ hours and systemic symptoms have substantially improved
Antigenic shift creates novel pandemic strains. Antigenic drift causes annual seasonal variation requiring reformulated vaccines