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4. RUBELLA (German measles)

Control Guideline

Last updated: 01 July 2012

1. Reason for surveillance

• To monitor the epidemiology of the disease to inform the development of better prevention strategies.

2. Case definition

Probable case (rubella)
A probable case requires:

• Clinical evidence, AND
• Laboratory suggestive evidence (pregnant women only) OR epidemiological evidence.

Laboratory suggestive evidence
(Pregnant women only)
In a pregnant patient detection of rubella specific IgM that has not been confirmed in a reference laboratory, in the absence of recent rubella vaccination.

Clinical evidence

• A generalised maculopapular rash, AND
• Fever, AND
• Arthralgia/arthritis, OR lymphadenopathy, OR conjunctivitis.

Epidemiological evidence
An epidemiological link is established when there is contact between two people involving a plausible mode of transmission at a time when:

• One of them is likely to be infectious (about one week before to at least four days after appearance of rash), AND
• The other has an illness which starts within 14 and 23 days after this contact, AND
• At least one case in the chain of epidemiologically linked cases (which may involve many cases) is laboratory confirmed.

Confirmed case (rubella)
A confirmed case requires laboratory definitive evidence only.

Laboratory definitive evidence

• Isolation of rubella virus, OR
• Detection of rubella virus by NAT, OR
• IgG seroconversion or a significant increase in antibody level or a fourfold, or greater rise in titre to rubella virus in the absence of recent rubella vaccination. The results must be established by the testing of paired sera in parallel, OR
• Detection of rubella-specific IgM, in the absence of recent rubella vaccination.

Note: that in pregnant women, the result needs to be confirmed in a reference laboratory.

Clinical evidence
Not applicable.

Epidemiological evidence
Not applicable.

Probable case (Congenital rubella syndrome)
A probable case requires:

• Laboratory suggestive evidence (either maternal or infant) AND
• Clinical evidence.

Laboratory suggestive evidence
Maternal evidence

• Isolation of rubella virus, OR
• Detection of rubella virus by nucleic acid testing
• IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre to rubella virus. This must be established by the testing of paired sera in parallel, OR
• Detection of rubella-specific IgM, in the absence of recent rubella vaccination AND confirmation of the result in a reference laboratory, OR

Infant evidence

• Detection of rubella-specific IgM in infant blood using capture EIA, OR
• Infant rubella antibody that persists at a higher level and for a longer period than expected from passive transfer of maternal antibody (i.e., rubella titre that does not drop at the expected rate of a two fold dilution per month).

Clinical evidence
As with confirmed case.

Confirmed case (Congenital rubella syndrome)
A confirmed case requires:

• Laboratory definitive evidence, AND
• Clinical evidence.

Laboratory definitive evidence

• Isolation of rubella virus from the infant, OR
• Detection of rubella virus, in the infant, by nucleic acid testing, OR
• Detection of rubella-specific IgM antibody in the serum of the infant AND confirmation of the result in a reference laboratory.

Clinical evidence
A live infant or still born foetus with ANY of the following compatible defects: cataracts, congenital glaucoma, congenital heart disease, hearing defects, microcephaly, pigmentary retinopathy, mental retardation, purpura, hepatosplenomegaly, meningoencephalitis, radiolucent bone disease.

Factors to be considered in case identification
False positive IgM results can occur; results should be confirmed for high risk cases (eg, pregnant women) by testing for IgM fractions after sucrose density centrifugation.
Maternal reinfection with rubella virus has been reported resulting in congenital infection. Its public health significance is unclear.

3. Notification criteria and procedure

Rubella is to be notified by:

• Laboratories on microbiological confirmation (ideal reporting by routine mail)
• School principals and directors of child care facilities (ideal reporting by telephone on same day of notification).

Probable and confirmed cases should be entered onto NCIMS.

4. The disease

Infectious agent
The rubella virus.

Mode of transmission
Rubella is transmitted by droplet infection and direct contact with nasopharyngeal secretions of infectios cases.

Timeline
The typical incubation period is 14 to 17 days, up to 21 days.
Rubella is communicable for about 7 days before and at least 4 days after rash onset.
Infants with congenital rubella syndrome may shed the virus for months after birth.

Clinical presentation
The usual clinical presentation is a mild febrile illness with a diffuse punctate and maculopapular rash. The rash typically starts on the face, becomming generalised over 24 hours and lats 3 days.

Children usually present with few or no constitutional symptoms, but adolescents and adults may have a 1 to 5 day prodrome of low-grade fever, headache, malaise, anorexia, mild coryza and conjunctivitis. Cervical lymphadenopathy (typically posterior auricular, posterior cervical and suboccipital lymph nodes) is characteristic and precedes the rash by 5 to 10 days. Asymptomatic infection is common.

Adolescents and adults (especially females) can sometimes develop transient polyarthralgia of fingers, wrists and knees.

Encephalitis and thromobocytopenia are rare complications.

Infection in pregnancy can result in congential rubella syndrome (see below), miscarriage or stillbirth. The risk of CRS is up to 90% if maternal infection occurs during the first 10 weeks of gestation. Defects are rare when maternal infection occurs after the 20th week of gestation.

Congenital rubella syndrome is characterised:

• Opthalmological: cataracts, pigmentary retinopathy, microphthalmos, and congenital glaucoma
• Auditory: sensorineural hearing impairment
• Neurological: behavioral disorders, meningoencephalitis, microcephaly and developmental delay.
• Cardiac: patent ductus arteriosus, pulmonary artery stenosis
• Other: growth retardation, interstitial pneumonitis, radiolucent bone disease, hepatosplenomegaly, thrombocytopenia.

5. Managing single notifications

Response time
Investigation
Within 1 working day of notification of a case of congenital rubella syndrome, begin follow-up investigation. Follow up other cases at the discretion of the PHU Director.

Data entry
Within 5 working days of notification enter probable and confirmed cases on NCIMS.

Response procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up, PHU staff should ensure that action has been taken to:

• Confirm the onset date and symptoms of the illness
• Confirm results of relevant pathology tests, or recommend the tests be done
• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview
Seek the doctor's permission to contact the case or relevant care-giver
• Review case management.
• For congential rubella, determine whether the woman was offered appropriate antenatal screening for rubella.
• Determine the case's immunisation history and in particular whether there is any evidence of immunisation with MMR vaccine.
• Determine if the case has had any contact with pregnant women during their infectious period. Women most likely to be susceptible include those born overseas (especially Asia, Pacific Islands, sub-Saharan Africa, South America), non-English speaking women and older women who were not offered rubella vaccination routinely.

Case management
Investigation and treatment
Supportive only.

Education
The case or relevant care-giver should be informed about the nature of the infection and the mode of transmission.

Emphasis should be placed on the importance of following the recommended immunisation schedule.

Isolation and restriction
Recommend exclusion from work, school, preschool, child care or other settings where there are susceptible individuals, especially young children, infants and pregnant women, for at least 4 days from the onset of rash.

Only people who are immune to rubella should have contact with an infant with congenital rubella syndrome. These children should be presumed infectious at least through to 1 year of age unless nasopharyngeal and urine cultures are negative for rubella virus after 3 months of age.

Environmental evaluation
None.

Contact Management
Identification of contacts
Direct contact with respiratory secretions from the case is generally considered significant. Contacts include people living in the same household, or who are in the same class, at the same social function, or work in the same area as the case.

Investigation and treatment
Passive Immunisation
Immunoglobulin given after exposure to an infectious case is not effective in preventing rubella infection.

Active Immunisation
MMR should be offered to susceptible contacts if they have no contraindications to vaccination. While MMR will not avert disease in those already infected and incubating infection, it may be effective in preventing subsequent infection if there is likely to be ongoing exposure.

All pregnant women with exposure to an infectious case should be offered urgent serological testing, irrespective of their history of previous vaccination, or history of past clinical infection or a positive rubella antibody result. Refer to Australian Immunisation Handbook for additional details.

Antibiotic Prophlaxis
None

Education
Susceptible contacts (or parents/guardians) can be alerted to the risk of infection through distribution of a factsheet through the school or workplace and they should watch for signs or symptoms of rubella occurring within 21 days of exposure. They should not have contact with pregnant women during this period.

Pregnant contacts should seek medical advice from their clinician for assessment of immunity and further counselling.

Exposed health care workers without adequate proof of immunity should be excluded from work for 21 days after exposure to an infectious case.