Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measure

Victorian statutory requirement

Rubella and congenital rubella syndrome (Group B disease) must be notified in writing within five days of diagnosis.

School exclusion: excluded until fully recovered or at least four days after the onset of the rash.

Infectious agent

Rubella virus of the Togaviridae family is the infective agent.

Identification

Clinical features
Rubella is a mild febrile viral illness characterised by a diffuse punctate and maculopapular rash. Children usually experience few or no constitutional symptoms but adults may experience a one to five day prodrome of low-grade fever, headache, malaise, mild coryza and conjunctivitis. Postauricular, occipital and posterior cervical lymphadenopathy is common and precedes the rash by five to ten days.

Complications include arthralgia and less commonly arthritis, particularly among adult females. Encephalitis is a rare complication.

Congenital rubella syndrome (CRS) occurs in less than 25% of infants born to women who acquire rubella during the first trimester of pregnancy. The risk of a single congenital defect falls to approximately 10–20% by the 16th week of pregnancy. Defects are rare when the maternal infection occurs after the 20th week of gestation.

Differential diagnosis includes measles, human parvovirus (‘slapped cheek’) infection, human herpesvirus 6 (roseola) infection and a large number of other rashes of varied aetiology.

Method of diagnosis
Clinical diagnosis should be confirmed by one or more of the following:

• demonstration of rubella-specific IgM antibody, except following rubella immunisation
• fourfold or greater rise in rubella antibody titre between acute and convalescent-phase sera obtained at least two weeks apart
• isolation of rubella virus from a clinical specimen.

Consider also testing for other similar exanthems such as measles and human parvovirus.

Incubation period

The incubation period is usually 14 to 17 days. It ranges from 14 to 21 days.

Public health significance & occurrence

Rubella occurs worldwide and is universally endemic except in remote and isolated communities. It is most prevalent in winter and spring.

A combined measles-mumps vaccine was first added to the routine childhood immunisation schedule in 1983. Although this has clearly led to a dramatic reduction in the number of reported cases the epidemiology of rubella infection in Australia is not clear because of the acceptance of clinical diagnoses without laboratory confirmation.

Routine serological testing of reported clinical cases of rubella in Victoria has revealed that only a small proportion of these cases can be confirmed in the laboratory. The remainder are likely to be due to other causes.

Unimmunised travellers and their unimmunised contacts remain at risk of infection.
Congenital rubella syndrome (CRS) was a major cause of congenital abnormalities including deafness prior to the infant immunisation program. Although CRS is now rare, the risk of infection remains for unimmunised pregnant women. Such women have been infected primarily by persons who have not been included in rubella vaccine programs.

Reservoir

Humans.

Mode of transmission

Rubella is transmitted by droplet spread or direct contact with infectious patients.
Infants with CRS shed the rubella virus in their nose, pharyngeal secretions and urine for months or even years.

Period of communicability

Rubella is communicable approximately one week before and for at least four days after the onset of the rash.

CRS infants may shed the virus for months or longer after birth.

Susceptibility & resistance

Immunity after natural disease is usually life long. Immunity after vaccination is long term and usually lifelong, although reinfection of vaccinees has been observed.

Passive maternal immunity is acquired transplacentally. Infants born to immune mothers are ordinarily protected for six to nine months depending on the amount of maternal antibodies transferred.

Control measures

Preventive measures
MMR vaccine is recommended in the ASVS for all infants at the age of 12 months and at again at four years of age.

Women of childbearing age should be tested for immunity to rubella prior to pregnancy if possible. All non-pregnant seronegative women should be offered rubella vaccine.

Women receiving rubella vaccine should be instructed to avoid pregnancy for 28 days after vaccination. Inadvertent rubella vaccination during pregnancy has not been associated with any CRS-like defects; it is not necessary to consider termination.

Women attending for antenatal care who are unaware of their immune status should be tested for rubella antibodies and if negative, be vaccinated immediately post partum.
All health care workers should receive MMR vaccine if not immune.

Control of case
There is no specific treatment.

The case should be excluded from school and childcare for at least four days after onset of the rash. Adults should not go to work for the same period of time.

Patients with rubella should avoid contact with other people while infectious, particularly pregnant women.

If a person with suspected rubella is pregnant, the diagnosis should be confirmed serologically and the patient referred to a specialist obstetrician for advice, taking care not to expose other pregnant women to possible infection in the process.

Control of contacts
School contacts should not be excluded from school regardless of immunisation status.

Although immunisation is generally recommended for non-immune contacts (except pregnant women) it is unlikely to reduce the risk of infection or illness. Immunoglobulin is not generally recommended, except for pregnant contacts.

Pregnant women in whom immunity to rubella has not been confirmed for the current pregnancy and who may have been exposed to rubella must be investigated serologically. This should occur irrespective of a history of vaccination, clinical rubella or previous positive rubella antibody.

Immunoglobulin should be considered after exposure to rubella in early pregnancy. It may not prevent infection or viraemia, but may modify abnormalities in the baby.

Control of environment
Not applicable.

Outbreak measures

All suspected outbreaks should be reported promptly to the Department of Human Services.

Mass immunisation may be recommended during an outbreak of rubella in a school regardless of immune status.