Is this boy’s illness a risk to his pregnant aunt?
Kevin is a four-year-old boy from Indonesia who is visiting family in Australia.
He presents with a three-day history of fever and a widespread, pruritic, maculopapular rash.
The rash began on his face and quickly spread to his entire body.
Kevin arrived in Australia two weeks ago. He is staying with his aunt, who is 22 weeks pregnant. Kevin was born in Indonesia and has not received any immunisations.
He was born at full-term, with normal growth and development.
According to his mother, he has previously had both chickenpox and measles.
On examination, Kevin appears generally well and is afebrile. There is a widespread, non-confluent maculopapular rash involving the entire body.
The maculopapules are pink and pinpoint.
Head and neck examination reveals non-tender bilateral post-auricular lymphadenopathy. There is no conjunctivitis and no mucosal changes suggestive.
The remainder of the examination is unremarkable.
A rubellaform rash.
The GP orders serology for measles, rubella, varicella zoster virus and parvovirus B19. The results of serological testing are summarised in table 1.
Supplemental testing on a second assay is also positive for rubella IgM.
|Table 1. Kevin’s viral serology results|
The testing laboratory notifies the GP of the likely diagnosis of acute rubella. The local public health unit is also notified and contacts the GP to assist with management.
The GP checks the aunt’s pre-conception serology, which reveals detected rubella IgG antibody (36 IU/mL) consistent with immunity.
Repeat serology on a newly collected specimen from the aunt confirms a high titre of rubella IgG antibody, with IgM not detected.
Further history does not reveal any other significant contact between Kevin and young children, or pregnant women during the infectious period.
Kevin himself is well and does not require any supportive management. His family is advised to isolate him from settings where young children, infants and pregnant women are likely to be until four days after the onset of rash.
Those who have had significant contact with Kevin, including everyone in the aunt’s household, are advised to avoid significant contact with pregnant women during the 21-day incubation period.
There are no secondary cases of rubella identified during the incubation period. Kevin’s aunt remains well, but is highly anxious. She is counselled that she is not at risk of passing on congenital rubella.
While Australia is well on the way to being declared free of endemic transmission of rubella, imported cases still occur. Rubella is a generally mild, self-limiting illness and is often asymptomatic.
It becomes significant when it is contracted during pregnancy as it places the fetus at risk of congenital rubella infection, with potentially severe morbidity and mortality. Contact with a pregnant woman during the infectious period is therefore of major public health importance.
Pregnant women with evidence of pre-conception immunity to rubella have no increased risk of maternal-fetal infection after contact with rubella, and their pregnancy can be managed routinely.
In non-immune women, the risk period for congenital rubella syndrome (that is, anomalies secondary to congenital rubella infection) is prior to 17 weeks’ gestation.
Congenital anomalies as a result of infection acquired after this time are rare.
Nevertheless, congenital infection from 18 weeks’ gestation onwards remains important because congenitally infected infants shed rubella virus throughout the first year of life and therefore pose an infection risk to others.
The incubation period for rubella is 14-21 days, with an infectious period spanning from seven days prior to four days post-onset of rash.
Significant contact is defined as contact with respiratory secretions, including household contacts and others who share the same class, social function or workplace during the infectious period.
Serological cross-reaction among rubella, parvovirus B19 and measles is common, and likely explains the equivocal parvovirus B19 IgM result in this case.
If there is a risk of congenital infection, specialist management by a team, including a maternal-fetal medicine specialist and an infectious diseases physician, is required.
Specialised testing, including rubella PCR on blood, urine and amniotic fluid, may be indicated.
Dr Jim Newcombe is a paediatrician, infectious diseases physician and clinical microbiologist at Royal North Shore Hospital and Douglass Hanly Moir, Sydney.
References on request.