Epidemiologic clues | Potential etiologies |
Age (0 to 28 days) | Infectious – CMV, HSV (type 1 or 2), enteroviruses, parechoviruses, rubella virus Noninfectious – Inborn error of metabolism (eg, organic acidemia, urea cycle disorder) |
Season: | |
Summer | Enterovirus, free-living amebae |
Late summer/fall | Arbovirus |
Winter | Postinfectious encephalitis in countries with low rates of MMR immunization |
Infection in horses, birds | Arbovirus, Hendra virus |
Blood transfusion or transplant recipient | CMV, EBV, HIV, rabies, tick-borne encephalitis, WNV |
Immunodeficiency | CMV, HHV-6, HSV, VZV, WNV, enterovirus (especially in X-linked agammaglobulinemia and common variable immunodeficiency) |
Historic clues | |
Rash | |
Vesicular | HSV, VZV, enterovirus (hand, foot, and mouth disease), herpes B virus |
Hand, foot, mouth | Enterovirus |
Erythematous macules and papules with cephalocaudad spread | Measles |
Maculopapular | WNV |
Maculopapular/petechial begins on ankles and wrists | Rocky Mountain spotted fever |
Exposures | |
Mosquitoes | Arbovirus |
Ticks | Borrelia burgdorferi, Powassan virus, Rickettsia rickettsii, tick-borne encephalitis |
Animal bite/exposure (dog, bat, cat, birds, livestock, others) | Rabies, arboviruses, cat scratch disease, Q fever |
Blood transfusion or transplant recipient | CMV, EBV, HIV, rabies, tick-borne encephalitis, WNV |
Recent infectious illness | ADEM |
Recreational activity | |
Swimming | Enteroviruses, free-living amebae |
Spelunking | Rabies |
Sexual activity | HIV, Treponema pallidum |
Travel | |
Immunization | |
Lack of immunization for specific agent | Japanese encephalitis, MMR, VZV, polio, tick-borne encephalitis |
Recent immunization | ADEM |
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