Measles infection is divided into four phases: incubation, prodromal (catarrhal), exanthematous (rash), and recovery. The incubation period is 8 to 12 days from exposure to symptom onset and a mean of 14 days (range, 7 to 21) from exposure to rash onset. The manifestations of the 3-day prodromal period
Viruses Adenovirus Measles Rubella Roseola (HHV-6 or HHV-7) Erythema infectiosum (fifth disease, parvovirus
Meningococcal infection (early) Salmonella typhi (typhoid fever, “rose spots”) Lyme disease (erythema migrans)
Rickettsiae Rocky Mountain spotted fever (early) Typhus (scrub, endemic) Ehrlichiosis
Bacteria Scarlet fever (group A streptococcus) Staphylococcal scalded skin syndrome Toxic shock syndrome (Staphylococcus aureus,
Bacteria M. pneumoniae Group A streptococcus Other Drug reaction Serum sickness
Vesicular, Bullous, Pustular
Bacteria Sepsis (meningococcal, gonococcal, pneumococcal, Haemophilus influenzae type b)
Fungi Necrotic eschar (Aspergillus, Mucor)
HBV, Hepatitis B virus; HHV, human herpesvirus.
are cough, coryza, conjunctivitis, and the pathognomonic Koplik spots (gray-white, sand grain-sized dots on the buccal mucosa opposite the lower molars) that last 12 to 24 hours. The conjunctiva may reveal a characteristic transverse line of inflammation along the eyelid margin (Stimson line). The classic symptoms of cough, coryza, and conjunctivitis occur during the secondary viremia of the exanthematous phase, which often is accompanied by high fever (40° C to 40.5° C [104° F to 105° F]). The macular rash begins on the head (often above the hairline) and spreads over most of the body in a cephalad to caudal pattern over 24 hours. Areas of the rash often are confluent. The rash fades in the same pattern, and illness severity is related to the extent of the rash. It may be petechial or hemorrhagic (black measles). As the rash fades, it undergoes brownish discoloration and desquamation.
Cervical lymphadenitis, splenomegaly, and mesenteric lymphadenopathy with abdominal pain may be noted with the rash. Otitis media, pneumonia, and diarrhea are more common in infants. Liver involvement is more common in adults.
The term modified measles describes mild cases of measles occurring in persons with partial protection against measles. Modified measles occurs in persons vaccinated before 12 months of age or with coadministration of immune serum globulin, in infants with disease modified by transplacental antibody, or in persons receiving immunoglobulin.
Routine laboratory findings are nonspecific and do not aid in diagnosis. Leukopenia is characteristic. In patients with acute encephalitis, the cerebrospinal fluid reveals an increased protein, a lymphocytic pleocytosis, and normal glucose levels. Measles virus culture is not generally available, though identification of measles RNA via reverse transcriptase-polymerase chain reaction (PCR) may be available through state public health departments or the Centers for Disease Control and Prevention (CDC). Serologic testing for IgM antibodies that appear within 1 to 2 days of the rash and persist for 1 to 2 months in unimmunized persons confirms the clinical diagnosis, though IgM antibodies may be present only transiently in immunized people. Suspected cases should be reported immediately to the local or state health department.