Smallpox and bioterrorism and the neurologist

Variola infection requires only a few drops inhaled from oral, nasal or pharyngeal mucosa. Infected patients may shed virions one or two days before symptoms until all scabs and crusts are shed. They are most infectious in first ten days. It produces an asymptomatic viremia, followed by a toxic viremia when it spreads to the spleen and other organs.

Neurologic symptoms include splitting headaches with pain over whole or just lumbar spine, hallucinations, delirium, depressive psychosis, manic depressive states that all may last into convalescence. Ocular disease (variola residua) may be bilateral with loss of sight from leukoma adherens or complications causing enucleation .

Intravenous cidofavir which is nephrotoxic may be useful. Smallpox vaccine (vaccinia virus) within seven days after exposure (incubation period) can prevent or attenuate the disease. Contraindications to preexposure vaccination are immunosuppression, HIV infection, pregnancy, or household sexual contacts with contraindications. Such patients should get vaccinia immune globulin with smallpox vaccine, but it may be unavailable.

Postvaccinial encephalitis is seen almost exclusively in those getting primary vaccination. In kids younger than 2 it can occur in 6-10 days,with most patients dying. In those older than 2, it has 35 % mortality, or those who recover do so within two weeks. Strain used may be important. Authors favor preexposure vaccination and stockpiling of vaccinia immune globulin. Eczema vaccinatum results from vaccinating an atopic patient or contacts of someone with eczema.

Pitfalls-- confusing generalized vaccinia, vaccinia necrosum or eczema vaccinatum with true smallpox, therefore rapid development of a pcr test is needed. Another pitfall is vaccinating an immunocompromised individual, that may have a 33 % mortality.