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What is rubella or German measles?
Hello and welcome to episode 93 of the Medical Fun Facts Podcast.
It’s Monday 20 November 2017. My name is Gary and the Medical Fun Facts Podcast is a weekly show with a few facts and hopefully one or two funny lines. Don’t expect too much and everything will be okay.
Last week, in episode 92 I spoke about “Q is for Q fever”, I also described the causative microorganism, viz., Coxiella burnetii.
Tonight, I’m speaking about R is for Rubella.
What is Rubella?
Let’s get the name out of the way first. Rubella is sometimes called German measles because it was first described by German doctors in the 1700s. Then in 1866, an English doctor called the disease Rubella which means ‘little red’.
We’ll get to congenital rubella syndrome (CRS) later but it’s worth mentioning here that it was an Australian eye doctor, viz., Norman Gregg, who first described CRS in the 1940s.
Rubella is usually characterised by a mild fever and a diffuse sharp-edged maculopapular rash. Clinically, rubella is difficult to distinguish from other causes of febrile rash illnesses, for example, due to measles virus, dengue virus, parvovirus B19, human herpesvirus 6, coxsackievirus, echovirus, adenovirus, or the bacterial disease scarlet fever.
Children often present with no systemic symptoms, but adults may experience a 1–5 day lead up consisting of low-grade fever, headache, malaise, mild coryza, and conjunctivitis. Swollen lymph nodes behind the ears, on the back of the head and neck, the most characteristic feature and occurs before the rash by 5–10 days. Sore joints occur in a significant proportion of infections, particularly in women. Brain infection is seen in 1 out of 6000 cases and occurs more commonly in adults. Up to 50% of rubella infections are either without rash or without any symptoms.
Rubella is important because it can produce an array of problems in the developing fetus. CRS may occur in up to 90% of infants born to women who are infected with rubella during the first 10 weeks of pregnancy. Fetuses infected early are at greatest risk of intrauterine death, spontaneous abortion, and CRS. Clinical manifestations of CRS include single or combined defects or symptoms such as hearing impairment, cataracts, microphthalmia, congenital glaucoma, microcephaly, meningoencephalitis, developmental delay, congenital heart defects, hepatosplenomegaly, and jaundice. Moderate and severe CRS is usually recognisable at birth; mild CRS with only slight cardiac involvement or hearing impairment may not be detected for months or even years after birth. Insulin-dependent diabetes mellitus is recognised as a frequent late manifestation of CRS. Congenital malformations and fetal death can also occur following unapparent maternal rubella. Defects are rare when maternal infection occurs after the 20th week of gestation.
Rubella is caused by the Rubella virus which is in the family Togaviridae and in the genus Rubivirus.
Laboratory diagnosis of rubella is required because clinical diagnosis is often inaccurate. Laboratory confirmation is usually based on the detection of rubella-specific IgM in a blood specimen obtained within 28 days after the rash onset. Other methods for rubella diagnosis include paired serum specimens that show seroconversion in rubella-specific IgG antibody titre, a positive rubella PCR test, and virus isolation.
This brings back fond memories for me. When I was 16 years old and in grade twelve I embarked on a high school science project which involved immunising mice to rubella and then testing them for antibodies using an enzyme immunoassay, hæmagglutination inhibition and a fluorescent antibody assay. It helped me develop a love for laboratory medicine. I entered the project into a national science competition but I was disqualified for live animal experimentation. A friend at school was also disqualified because he developed solid rocket fuel.
Laboratory confirmation of CRS in an infant is based on a positive rubella-specific IgM assay, the persistence of a rubella-specific IgG beyond the time expected from passive transfer of maternal IgG antibody, isolation of the virus from a throat swab or urine specimen, or detection of rubella virus by PCR. Almost all infants with CRS have a positive rubella IgM test from 0–3 months old, and more than 30% of infants remain positive from 4–9 months old. Rubella virus has been isolated from throat and urine specimens of infants with CRS and from cataract surgery aspirates in children up to 3 years of age.
In the absence of immunisation programs, rubella occurred worldwide endemically with epidemics every 5–9 years. In years gone by, large rubella epidemics resulted in very high levels of morbidity including lots of cases of CRS. So, for the people who are opposed to national immunisation programs, the US epidemic in 1964–1965 led to an estimated 12.5 million cases of rubella, more than 20,000 cases of CRS, and 11,000 fetal deaths; the incidence of CRS during endemic periods was 0.1–0.2 per 1000 live births and 1–4 per 1000 live births during epidemics.
The incubation period for rubella is from 14–17 days with a range of 14–21 days.
Rubella is transmitted by contact with nasopharyngeal secretions of infected people. The period of communicability is about 1 week before and at least 4 days after onset of rash. Infants with CRS may shed virus for up to 1 year after birth.
Immunity is usually permanent after natural infection and possibly lifelong, after immunisation. Infants born to immune mothers are ordinarily protected for 6–9 months, but it depends on the amount of maternal antibody acquired transplacentally.
There is no treatment for Rubella, however, in high risk patients some doctors may try normal immunoglobulin hoping it contains enough antibody to prevent infection in someone with a definite exposure. The best way to prevent infection and maintain long term immunity and population safety is by national immunisation programs that use a live attenuated virus, usually combined with live attenuated Measles and Mumps viruses.
Questions for readers and listeners
Have you ever heard of German measles and congenital Rubella syndrome?
Were you aware of the Australian connection with CRS?
Did you know you can successfully immunise mice against rubella even though mice are not normally infected?
Please leave your answers in the comments section of the show notes or on the Facebook page or on YouTube.
That’s episode 93 in the can.
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I’ll catch you next week for episode 94. Something beginning with the letter S. Send me suggestions.
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Thank you, and good night.