Tetanus

Generalized tetanus (most common, incubation 3–21 days):

• Trismus ("lockjaw"): inability to open the mouth due to masseter muscle spasm — often first sign

• Risus sardonicus: characteristic fixed smile from facial muscle spasms

• Opisthotonus: arching of the back from paraspinal muscle rigidity

• Generalized painful muscle spasms triggered by touch, noise, or light

• Dysphagia (difficulty swallowing)

• Autonomic instability: hypertension, tachycardia, profuse sweating, hyperpyrexia

Neonatal tetanus (umbilical stump contamination):

• Poor feeding, excessive crying, muscle spasms in first 2 weeks of life — ~50% fatal without treatment

Localized tetanus: Spasms limited to the site of injury; may progress to generalized.

The risk of tetanus is determined primarily by vaccination status and the nature of wound exposure. Unlike most infectious diseases, tetanus has no person-to-person transmission component.

Risk factors for acquiring tetanus:

• Incomplete or absent vaccination: The single most important risk factor. In high-income countries, tetanus occurs almost exclusively in unvaccinated or under-vaccinated individuals (elderly who missed childhood vaccines, immigrants from countries with low coverage, individuals who declined vaccination).

• Wound characteristics: Puncture wounds (especially from nails, thorns, or splinters), crush injuries, wounds contaminated with soil or manure, burns, frostbite, avulsions, and compound fractures create anaerobic conditions favorable for spore germination. However, tetanus can follow minor injuries — in ~20% of cases, no wound is identified.

• Injection drug use: Particularly subcutaneous injection ("skin popping") of contaminated drugs. Wound botulism should be co-considered.

• Neonatal risk: Unclean delivery practices (cutting the umbilical cord with non-sterile instruments, applying traditional substances to the umbilical stump) in infants of unimmunized mothers.

• Surgical and procedural risk: Post-surgical tetanus (rare) following gastrointestinal surgery, dental procedures, or intramuscular injections with contaminated needles.

Risk factors for severe disease and poor outcomes:

• Age: Case-fatality rate increases sharply in neonates and in adults aged >60 years. In the elderly, both incomplete immunity and reduced physiological reserve contribute.

• Short incubation period: Incubation <7 days (and especially <48 hours between the first symptom and the first spasm — the "onset time") predicts more severe disease.

• Delayed treatment: Access to ICU care with mechanical ventilation and autonomic management is the major determinant of survival in severe cases. Resource-limited settings have CFR 50–70% vs. 10–20% in well-equipped ICUs.

• Wound proximity to CNS: Cephalic tetanus (head wounds, otitis media) may progress rapidly.

• Portal of entry: Neonatal tetanus (umbilical route) and post-abortive tetanus carry particularly high mortality.

Populations at elevated risk in high-income countries:

• Elderly (waning immunity, often >30 years since last booster)

• Agricultural workers and gardeners

• Injection drug users

• Immigrants and refugees from low-coverage countries

• Respiratory failure: most common cause of death; laryngospasm or prolonged respiratory muscle spasm

• Autonomic dysfunction: life-threatening hypertensive crises, labile blood pressure, cardiac arrhythmias

• Aspiration pneumonia: from dysphagia and impaired protective reflexes

• Rhabdomyolysis: from severe, prolonged muscle spasms — can cause acute kidney injury

• Fractures: vertebral fractures from violent opisthotonus

• Nosocomial infections: from prolonged ICU stay

• Long-term: fatigue, anxiety, PTSD after severe episodes