Measles virus

From IDWiki
(Redirected from Measles)
  • Highly contagious virus that causes a triad of cough, coryza, and conjunctivitis

Background

Microbiology

  • Enveloped RNA Morbillivirus in the Paramyxoviridae family
    • Family includes parainfluenza, RSV, measles, mumps
  • Eight structural proteins: F, C, H (haemagglutination), L (large), M (matrix), N (nucleoprotein), P (phosphopolymerase), and V
    • N, P, and L complex with RNA
    • C and V interact with cellular proteins and regulate replication
    • M, H, and F are viral envelope proteins
    • H helps with host cell attachment, and F helps with spread between cells

Pathophysiology

  • Airborne droplets can remain in the air up to 2 hours after a person with measles has coughed
    • It is droplet, but just very small droplet
  • Innoculated through respiratory mucosa, enters lymphoid cells via SLAM receptor
    • SLAM (CDw150) is present on lymphocytes and antigen-presenting cells
  • Spreads to entire respiratory systems, as well as intestines, bladder, skin, and spleen, lymph nodes, liver, conjunctiva, and brain
  • Propagates within T and B lymphocytes and monocytes, but also endothelial, epithelial, and dendritic cells
  • Host response success causes disappearance of serology and appearance of rash
    • Possibly the rash represents a hypersensitivity reaction to the virus mediated by cellular immunity

Epidemiology

  • Infection confers lifelong immunity, though vaccination may not
  • Worldwide distribution
  • Prior to vaccination, there were epidemics every 2 to 5 years lasting 3 to 4 months
  • Vaccine hesitancy is becoming more common
    • Parts of Europe

Clinical Manifestations

  • Incubation period 10 to 14 days (range up to 21 days), followed by several days of prodrome that includes fever, anorexia, cough, coryza, and conjunctivitis
    • Can be mistaken for common cold or for Kawasaki disease
    • Koplik spots appear at end of prodrome
      • Bluish gray specks on a red base in the oral mucosa ("like grains of sand")
  • Rash follows Koplik spots
    • Spreads from face to body, including palms and soles
    • Fevers resolve soon after rash appears
    • Rash is erythematous and maculopapular, and my desquamate as it begins to heal
    • Usually lasts 5 days, clearing in the same pattern that it appeared
  • The rash disappears about 7 to 10 days after late prodromal period, with cough being the last symptom to disappear

Complications

  • Respiratory involvement, either as primary infection of with bacterial superinfection
  • Acute encephalitis in 1 in 1000-2000 patients, with new fevers, headaches, seizures, and altered level of consciousness
    • Likely from hypersensitivity to virus in the brain rather than from direct infection
    • Sequelae include blindness, corneal scarring
  • Chronic encephalitis, also called subacute sclerosing panencephalitis
  • Hepatitis
  • Complications are more common in adults who are infected

Subacute Sclerosing Panencephalitis (SSPE)

  • Degenerative neurological condition caused by persistent CNS infection despite immune response
  • 5-10 years after infection
  • Higher risk if infection before age 2 years
  • Inevitably ends in death

Special Populations

Modified Measles

  • Patients with passive immunity to measles may present with a milder form
    • Babies with mom's immunoglobulin, or patients who have received immune globulin
  • The prodrome, Koplik spots, and rash are often absent, and it is sometimes subclinical

Atypical Measles

  • Patients with prior immunization with killed vaccine (no longer on market, since 1960s) may have an atypical presentation
  • Prodrome of fever and pain for 1 to 2 days
  • Rash follows, but moves peripherally to centrally, and have varied form (urticarial, maculopapular, hemorrhagic, vesicular)
  • Fever continues, with edema, interstitial pneumonia, hepatitis, and occasionally pleural effusion
  • More prolonged course, with very high antibody titres

Immunocompromised

  • Chemotherapy, transplantation, AIDS, and congenital cellular immunodefieciency are all risk factors for severe measles
    • Possibly also malnutrition
  • Can develop giant cell pneumonia, without rash, as well as a chronic encephalitis
    • Can detect measles RNA in brain tissue

Pregnancy

  • Can be severe
  • Can cause spontaneous abortion and premature delivery
  • Newborn can be infected; they should get immune globulin at birth

Differential Diagnosis

Diagnosis

  • Typically diagnosed clinically; CBC may show leukopenia
  • If uncertain of the diagnosis, can use serology or molecular tests to confirm
    • NP swab PCR within 7 days of rash onset
    • Urine PCR within 14 days of rash onset
    • ELISA IgG serology, repeated after 1 week; fourfold titre increase is diagnostic
      • Or IgM, if available, to diagnose on one sample
      • IgM can persist for up to a month
    • Viral culture is also possible
  • For SSPE, can demonstrate high titres in serum and CSF

Management

  • Most infectious just before rash; quickly becomes non-infectious after end of prodrome
  • Supportive care
  • Vitamin A can be given, especially if the child is deficien
    • In children >1 year, vitamin A 200,000 IU daily for 2 days
    • If 6-12 months old, use 100,000 IU for 2 days
    • Less than 6 months, use 50,000 IU
    • If deficient, give another dose at 2 to 4 weeks
  • Ribavirin unhelpful but sometimes given

Prevention

Infection Control

  • Infectious period is 5 days prior to until 4 days after onset of rash
  • Need to do contact tracing, including people up to two hours after any room they were in
  • All contacts should be quarantined at home regardless of symptoms
    • Susceptible contacts should be placed in airborne precautions from 5 days after first exposure to 21 days after last exposure

Post-Exposure Prophylaxis (PEP)

  • Use either MMR vaccine or immune globulin in susceptible people
  • Immunization
    • Should be offered to all susceptible, immunocompetent people age 6 months and older
    • Give within 72 hours of exposure
    • Can shorten the time to rash, suggesting a shorter period of infectiousness
  • Immunoglobulin can provide short-term protection to certain susceptible, immunocompromised people
    • Given to people with high risk for severe or fatal measles and are susceptible:
      • Susceptible pregnant women
      • Susceptible immunocompromised people
        • Regardless of prior vaccination, should also be considered in advanced HIV
        • Regardless of prior vaccination, should also be consider in all patients with hematopoietic stem cell transplantation until they have been revaccinated post-transplant with confirmed adequate antibody titres
      • Susceptible infants <6 months of age
      • Susceptible immunocompetent infants from 6 to 11 months of age who present after 72 hours
    • Give within 6 days of exposure
Population Time since measles exposure
≤72 hours 73 hours to 6 days
Susceptible infants <6 months old IMIg 0.5 mL/kg
Susceptible immunocompetent infants 6-12 months old MMR IMIg 0.5 mL/kg
Susceptible immunocompetent people ≥12 months old MMR
Susceptible pregnant people IVIg 400 mg/kg (preferred) or IMIg 0.5 mL/kg
Immunocompromised individuals IVIg 400 mg/kg (preferred) or IMIg 0.5 mL/kg
People with confirmed immunity None

Vaccination

  • Live vaccine (given in MMR or MMRV) at 12-15 months, with a booster later in childhood between 18 months and school entry
    • Wait at least 5-6 months after receiving immunoglobulin
    • Wait at least 4 weeks from a dose given before 12 months for post-exposure prophylaxis
  • No adverse effects of revaccination
  • Rates need to be >95% to prevent imported cases from causing outbreaks
  • Rates less than 80% allow endemic transmission with cyclical outbreaks every 3-5 years
  • Vaccination is contraindicated in advanced HIV, other cell-mediated immunodeficiency, and in pregnancy
    • Wait 3 months after chemotherapy
    • Don't use MMRV, since no safety data are available
  • Can be associated with anaphylaxis in patients with true egg allergy

Vaccine Failure

  • Improper storage >4º C
  • Failure to use proper diluent for lyophilized vaccine
  • Exposure to light or heat
  • Vaccination in the presence of passive antibody

Catch-Up

  • 2 doses of MMR at least 4 weeks apart

Further Reading