Microbiology
Pathogens
Regarding rubella, which of the following statements is INCORRECT:
Answer:
The risk of congenital rubella syndrome is highest in the first trimester. Congenital rubella syndrome (CRS) occurs in 90% of fetuses when rubella is contracted in the 11th week (or before) of pregnancy, and 20% of fetuses when rubella is contracted in the 11th to 16th weeks of pregnancy. There have been no published case reports of CRS after 20 weeks' gestation.Rubella
Microbiology / Pathogens / Measles, Mumps and Rubella
Last Updated: 4th July 2020
| Virus | Rubella |
|---|---|
| Transmission | Respiratory droplet route or transplacentally |
| Incubation period | 14 - 21 days |
| Relation of infectivity to rash | Patients are infectious from 7 days before the rash appears and until 4 days after the rash appears |
| Relation of infection to immunity | Natural infection is followed by lifelong immunity |
| Clinical features | Prodromal phase (fever, malaise, sore throat) precedes fine red maculopapular rash (appearing first on the face and spreading downwards) associated with lymphadenopathy (suboccipital and postauricular nodes) and arthralgia, symptoms last 7 - 10 days |
| Complications | Arthritis, encephalitis, congenital rubella syndrome (deafness, cataracts, cardiac defects, microcephaly, cognitive impairment, intrauterine growth restriction) |
| Diagnosis | ELISA or NAAT of saliva |
| Treatment | Supportive, notifiable disease |
| Vaccination | MMR vaccine given at one year and preschool age |
Transmission and Epidemiology
Rubella is rare in countries with a vaccination programme. Transmission is by the respiratory droplet route and transplacentally. The incubation period is 14 - 21 days. Patients are infectious from 7 days before the rash appears until 4 days after the rash resolves. Natural infection is followed by lifelong immunity.
Clinical Features
Symptoms are often mild, and up to 50% of infections may be subclinical or inapparent.
A prodrome of mild low-grade fever, malaise and sore throat usually precedes development of a widespread fine red maculopapular rash (usually appears first on the face, and then spreads to trunk and limbs, fades in 3 - 5 days) associated with lymphadenopathy (suboccipital and postauricular nodes) and arthralgia.
Complications
Complications include:
- arthritis
- encephalitis
- congenital rubella syndrome
- maternal infection may cause foetal death or severe abnormalities such as sensorineural deafness, cataracts, cardiac defects, microcephaly, intrauterine growth restriction and cognitive impairment; the risk is highest during the first trimester and decreases in subsequent trimesters
Diagnosis
Diagnosis is with ELISA or NAAT of saliva.
Treatment
Treatment is supportive. There are no specific treatments for rubella.
Prevention
Infected individuals should stay away from school for 4 days from onset of the rash.
The MMR vaccine is given at 1 year and at preschool age (three years four months old).
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
