Measles virus is associated with the following clinical syn-dromes: (a) measles, (b) atypical measles, and (c) subacute sclerosing panencephalitis.
Incubation period varies from 8 to 12 days. Measles is a highly contagious febrile illness. The prodromal phase is character-ized by high fever, malaise, anorexia, conjunctivitis, cough, and coryza. Koplik’s spot is the typical pathogenic lesion found in the mucous membrane.
Koplik’s spots: These are bluish gray specks or grain sub-stance on a red base, which usually appear on the buccal mucosa opposite the second molar. They appear at the end of prodrome, just before the appearance of rash. These Koplik’s spots may also appear on the mucous membrane of the con-junctiva and vagina. Koplik’s spots usually appear after 2 days of illness. These spots, which last for 24–48 hours, are pathog-nomonic of measles. Their presence establishes the diagnosis of measles.
An erythematous maculopapular rash appears within 12–24 hours of appearance of the Koplik’s spots. The rash usu-ally begins on the face, then spreads extensively and appears on the trunk, extremities, palms, and soles and lasts for about 5 days. Desquamation of the rashes except those of palms and soles may occur after 1 week. Patients appear highly sick during the first or second day of the appearance of the rash. The rash is typically absent in patients with defective CMI. Generalized lymphade-nopathy and mild hepatomegaly may also occur in some patients.
Complications of measles: Complications include otitismedia, bronchopneumonia, laryngotracheobronchitis (croup), and diarrhea. Bronchopneumonia is a most serious condition and is responsible for 60% of deaths caused by measles virus. Hepatitis, encephalitis, and SSPE are the rare complications. Encephalitis is one of the most dangerous complications and occurs approximately in one of every 1000 patients. Measles causes death mostly in children younger than 5 years. It causes high mortality in (i) infants between 4 and 12 months and (ii) children who are immunocompromised because of human immunodeficiency virus (HIV) infection or other diseases.
Atypical measles is a syndrome that has been described in peo-ple who were infected with measles virus after immunization with the older, killed measles vaccine used during 1963–1977. This condition also occurs, but rarely, in individuals vaccinated with attenuated virus vaccine. The condition is characterized by a prolonged high fever, pneumonitis, and the rash. The rash characteristically begins peripherally and may be urti-carial, maculopapular, hemorrhagic, or vesicular. The condi-tion appears to be immune mediated and to occur as a result of hypersensitivity to measles virus in a partially immune host. This condition is associated with a low measles antibody titer early in the course of infection but a very high measles IgG anti-body titer during the course of infection (e.g., 1:1,000,000).
The subacute sclerosing panencephalitis (SSPE) is a degenerat-ing disease of the CNS caused by persistent measles infection. It is the most serious and late neurological sequelae of mea-sles that affects the CNS. The disease is characterized by the development of behavioral and intellectual deterioration and seizures after many years (mean incubation period is 10.8 years) of infection by measles.
The condition occurs in about seven in every 1 million patients. The condition occurs most commonly in children who were initially affected when they were younger than 2 years. The condition is associated with the presence of an extremely high measles antibody titer in the blood and cerebrospinal fluid (CSF).