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Laboratory confirmation

Whenever someone is suspected to have measles, it is imperative that laboratory confirmation of the illness be achieved. Since laboratory results may not be available for several days to several weeks, but prophylaxis of susceptible contacts has to occur within 6 days of exposure, outbreak control activity has to proceed while laboratory tests are processed.

To confirm measles, serologic testing or viral culture methods are available. Whenever laboratory specimens to confirm measles are collected, please call the health department at the number provided below. We can expedite testing through our laboratory or the state health department laboratory. Often same or next day results are available, and there is no charge to the patient.

Serology

Draw at least 1ml (2 ml is best) of sera or 4-5 ml blood (8-10 ml is best) in a red or tiger top tube (tubes without anticoagulants or preservatives). Please notify your laboratory that you would like the serologic specimens to go to the local or state health department for testing, otherwise you may be surprised to find that the test result was delayed or inaccurate because the specimen was sent to a distant private laboratory. The state laboratory routinely performs rubella Igm and IgG testing on all specimens submitted for measles testing.

  • Measles IgM
    This is an antibody test that measures the presence of a specific antibody class(IgM) that is only present during acute illness. For the best results, draw samples for measles IgM testing 3 or more days after rash onset. Serologic specimens can be drawn sooner than this as 70-85% of true measles cases will demonstrate IgM antibody by the day of rash onset, however if the test result is negative, the patient should know that another specimen may be required. By the third day after rash onset, 99% of true measles cases will demonstrate IgM antibody.

    The Washington state laboratory uses the measles IgM capture technique, which is the most specific and sensitive test available. Unfortunately private laboratories use commercially available test kits that often yield false positive results, because there is frequent cross reaction with other viral agents.

  • Measles IgG
    Both acute and convalescent sera are necessary to determine whether there has been a four fold or greater rise in total measles antibody. To perform the test, draw the first sample during the acute illness and the second (convalescent specimen) 2 to 3 weeks later. The laboratory should determine the antibody results of both specimens in the same laboratory run.

Viral cultures

These tests look for measles virus. Cultures results are available within 1 to 3 weeks.

  • Nasal wash
    Swab the posterior nasal passage with a Dacron™ or rayon swab and place the swab in 2–3 ml of viral transport medium.

  • Urine
    This is the preferred viral culture technique. Collect 50 to 100 ml of clean voided urine in a sterile container. Urine must be collected as soon as possible and no later than one week after rash onset.

  • Blood
    Collect 5 to 10 ml of blood in a heparinized tube. Please note: Heparinized tubes are used here while measles antibody tests require the use of tubes without anticoagulants.

It is also valuable to conduct laboratory tests appropriate to rule out other potential causes. An example would be a throat culture to look for evidence of streptococcal infection.

Routine measles, mumps and rubella (MMR) immunization recommendations

  • All children ages 12 to 15 months and older, and adults born in or after 1957, should be immunized against measles.
  • Two doses of vaccine are recommended: the first at age 12 to 15 months and the second at entry to kindergarten or 6th grade (depending on year of birth).
  • Older children and college entrants who have had only one dose of MMR should be given a second dose. (The minimum interval between doses is 1 month.)
  • Immunizations given before the first birthday or before 1968 should not be counted as valid and should be repeated.

Contraindications

Children between 12 to 15 months and 5 years of age without documentation of prior MMR who present themselves to medical facilities for any reason should be immunized. In previous measles outbreaks, many of the children with measles had opportunities for immunization at prior office visits.

The only valid contraindications to MMR in children are moderate to severe acute illness, anaphylactic allergy to eggs or neomycin, significant immunosuppression, or recent receipt of immune globulin products or blood.

Children with asymptomatic or mildly symptomatic HIV infection can be given MMR, as well as children with leukemia in full remission who have been off chemotherapy for at least 3 months.

Health care staff

Health care staff with patient contact born in 1957 or later should have either two documented live measles vaccinations, the first given on or after the first birthday and after 1968 (some vaccines given prior to 1968 were ineffective) or evidence of serologic immunity. It is not necessary to check immune status prior to immunization, however, as persons already immune should experience no significant side effects from additional MMR doses.

Staff born prior to 1957 usually do not require an immunization nor serologic testing as they are probably immune due to a disease exposure in childhood.

Prevent spread of measles

Medical facilities should promptly screen walk-in patients; every effort should be made to isolate persons with suspected measles. Options include having the patient stay in the car, using a separate door or room, and having the patient wear a face mask when going to the lab, etc. To the extent possible, well child exams should not be scheduled at the same time that measles cases are likely to be seen. Note that airborne transmission via aerosolized droplet nuclei has been documented in closed areas (e.g., exam rooms) for up to 2 hours after a person with measles occupied the area.

Recommendations for managing measles exposures in health care facilities

  1. Identify presumed susceptible patients, staff, and visitors potentially exposed to the case. Cases are infectious up to 5 days before through 4 days after rash onset.

  2. While collection of acute sera for measles IgM testing and paired acute and convalescent IgG sera is appropriate, action to prevent infection spread cannot wait for lab results but must be undertaken based on clinical diagnosis.
    1. Potential exposures: those with room contact with the case or those who shared room space (within 2 hours) recently occupied by the case.
    2. Presumed susceptible: persons born in 1957 or later without either documented evidence of two doses of valid measles vaccine or evidence of seroimmunity; persons born before 1957 without either documented evidence of one dose of valid vaccine or seroimmunity. Note: measles vaccine given before one year of age or before 1968 should not be counted as valid doses.

  3. Immunoprophylaxis of exposed susceptible contacts:
    1. Measles vaccine given within 3 days after first exposure is sometimes successful in preventing infection. Immune globulin (IG) is effective in preventing or modifying illness if given within 6 days after first exposure. Protection lasts up to 5 months. IG is recommended primarily for the following exposed persons:
      • Infants under 1 year of age without previous measles vaccination
      • Susceptible pregnant women
      • Immunocompromised persons
    1. Dosage of IG:
      • 0.11 ml/lb (0.25ml/kg) of body weight, IM. Maximum dose=15 ml. Give no more than 5 ml in one site.
      • Immunocompromised persons--0.22 ml/lb (0.5 ml/kg) of body weight. Maximum dose=15 ml.
      • MMR should be given 5 or more months later (when passively acquired antibodies should have disappeared) to confer long term protection.
  1. Notify exposed persons, even if immunized or given IG,
    that they may develop measles within the next 3 weeks. There may be an extension of the incubation period due to the administration of IG. People who have received IG often have mild symptoms.

  2. If an exposed person develops the prodromal symptoms
    (fever, cough, coryza, photophobia, conjunctivitis), they should isolate themselves. If they need medical attention, they should call ahead to alert medical staff so as to avoid exposing other patients. They should also inform the health department by calling the numbers given below.

  3. Exposed susceptible staff:
    • If a specimen drawn within 6 days after exposure shows measles IgG, or total antibody, consider the person immune.
    • If the staff member has had 1 dose of measles vaccine given in 1968 or later and after the first birthday, give an additional dose of vaccine. If the second vaccine dose can be given within 72 hours of the exposure, consider the person immune. If it can not be done within 72 hours, draw measles antibody test, and consider the person immune if the test shows antibody.
    • If a staff member has had 2 doses of measles vaccine given after 1968 and after the first birthday, consider the staff person immune.
    • Exposed susceptible staff should be relieved of direct patient contact from the 6th to the 20th day after exposure, even if they were given vaccine or IG after exposure. (If they develop measles, they should avoid patient contact until at least 4 full days after rash onset.) If this is truly impossible, staff should have their temperatures taken and be asked about prodromal symptoms as they come to work from days 6 through 20 after exposure. They should immediately be sent home if temperature is over 99.6ºF or prodromal symptoms are present. This screening procedure must be followed rigorously to prevent staff members with prodromal phase measles from infecting others.
  1. During community-wide outbreaks, triage should be considered at the door of all medical facilities to separate possible measles cases from others. Signs should be posted at the door advising possible cases not to enter without special arrangements being made. When isolation measures are impossible, consider disposable face masks for the patients with possible measles.

  2. If admitted, patients should remain on respiratory isolation
    until the end of the fourth day after rash onset. Immunocompromised patients should be in isolation for the duration of their illness.

References

  • Measles Prevention: Recommendations of the Immunization Practices Advisory Committee (ACIP). MMWR 1989; 38(No.S-9):1-13.
  • American Academy of Pediatrics: Report of the Committee on Infectious Diseases, 21st edition. 1994, AAP, Elk Grove Village, Illinois.
  • Atkinson, WL. Measles and health care workers. Infect Control Hosp Epidemiol 1994; 15:5-7.