Microbiology
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Pathogens
A pregnant patient presents to ED with a new onset rash which started on her face and spread to her body. She has recently been in contact with a child with rubella. Infection with rubella virus causes the most damage at what stage of pregnancy:
Answer:
Rubella is very dangerous for a pregnant woman and her developing baby. Infection with rubella virus causes the most severe damage when the mother is infected early in pregnancy, especially in the first 12 weeks (first trimester). Congenital rubella syndrome (CRS) is a condition that occurs in a developing baby whose mother is infected with the rubella virus. Pregnant women who contract rubella are at risk for miscarriage or stillbirth, and their developing babies are at risk for severe birth defects with devastating, lifelong consequences. CRS can affect almost everything in the developing baby’s body. The most common birth defects from CRS can include:- Deafness
- Cataracts
- Heart defects
- Intellectual disabilities
- Liver and spleen damage
- Low birth weight
- Skin rash at birth
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 |
