Microbiology
Pathogens
Regarding measles, which of the following statements is CORRECT:
Answer:
Natural infection with measles is followed by lifelong immunity. Measles is transmitted via the respiratory droplet route. The incubation period is about 9 - 12 days and individuals are considered infectious from 3 days before the rash develops. Treatment is usually supportive, antibiotics may be required for secondary bacterial infection.Measles
Microbiology / Pathogens / Measles, Mumps and Rubella
Last Updated: 21st April 2019
| Virus | Measles |
|---|---|
| Transmission | Respiratory droplet route |
| Incubation period | 9 - 12 days |
| Relation of infectivity to rash | Patients are infectious from about 3 days before rash emerges to 4 days after |
| Relation of infection to immunity | Natural infection is followed by lifelong immunity |
| Clinical features | 2 - 4 day prodromal phase (fever, coryza, cough, conjunctivitis), Koplik spots (white papules on buccal mucosa), maculopapular rash appearing first behind the ears and spreading to whole body, rash resolves after 7 - 10 days |
| Complications | Secondary bacterial infection (pneumonia, bronchitis, otitis media), encephalitis, subacute sclerosing panencephalitis |
| Diagnosis | ELISA and immunofluorescence of saliva/blood, viral culture of buccal/nasopharyngeal swab |
| Treatment | Supportive treatment, notifiable disease |
| Vaccination | MMR vaccine given at one year and at preschool age |
Transmission and Epidemiology
Measles is transmitted by the respiratory droplet route. The incubation period is about 9 - 12 days and individuals are infectious for about 3 days before the rash emerges. Natural infection is followed by lifelong immunity.
Mortality is rare, but is higher in patients who have HIV, are immunocompromised, malnourished, or are under 2 years old. Measles is rare in countries with a vaccination programme (but has become more prevalent of late due to a failure of uptake of vaccination).
Clinical Features
A prodromal 2 - 4 day coryzal illness (fever, cough, conjunctivitis, irritability) normally occurs associated with Koplik's spots (small white papules found on the buccal mucosa near the first premolars), before a morbilliform maculopapular rash appears, first behind the ears and then spreading downwards to whole body. The rash peels off or fades about about 7 - 10 days.
Complications
Complications may include:
- secondary bacterial infection
- pneumonia
- otitis media
- bronchitis
- encephalitis
- subacute sclerosing panencephalitis
- a rare, progressive, fatal encephalitis that develops 7 - 10 years after infection, usually in children who had a primary infection before the age of 2
- a progressive loss of neurological function results in spasticity, seizures and eventually death
Diagnosis
Measles is unlikely in a fully immunised individual. Following assessment, if a diagnosis of measles is considered likely, it is essential to notify the local Health Protection Unit (HPU), and the infection should be confirmed through laboratory investigation. Investigations may include ELISA, immunofluorescence of saliva or blood or viral culture of buccal or nasopharyngeal swab.
Treatment
Treatment is supportive and measles will usually resolve over a course of 7 - 10 days. Antivirals may be considered in patients at particularly high risk.
Prevention
Infected patients should be isolated to prevent spread. Patients are considered infectious for 3 days before the rash emerges and are advised to stay away from school/nursery/work for four days from onset of the rash.
The measles, mumps and rubella vaccination 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 |
