Microbiology
Pathogens
Regarding hepatitis A, which of the following statements is CORRECT:
Answer:
Transmission is by the faecal-oral route and the incubation period is about 2 - 6 weeks. Chronic hepatitis does not occur. Treatment is supportive, antivirals have no clinical benefit. A hepatitis A vaccine is available recommended for travellers to high prevalence areas, patients with chronic liver infections and individuals with high risk occupations e.g. healthcare workers, sewage workers.Hepatitis A
Microbiology / Pathogens / Hepatitis
Last Updated: 21st April 2019
Transmission
Hepatitis A transmission is by the faecal-oral route; the virus is excreted in bile and shed in the faeces of infected people. Faecal shedding has been demonstrated for 2 - 3 weeks before and about a week after, the onset of jaundice. The incubation period is about 2 - 6 weeks.
Institutional outbreaks may occur in summer, and point-source outbreaks follow faecal contamination of water or food e.g. oysters.
Clinical features
Hepatitis A is the most common cause of infective hepatitis worldwide.
Asymptomatic infection is more common in children, with the risk of symptomatic disease increasing with age. Most people made an uneventful recovery.
- Prodromal phase (duration 2 days - 2 weeks)
- Flu-like symptoms (headache, malaise, fever, myalgia)
- Gastrointestinal symptoms (anorexia, nausea/vomiting, diarrhoea, RUQ discomfort)
- Icteric phase (duration 1 - 3 weeks)
- Jaundice, pruritus, anorexia, hepatomegaly, hepatic tenderness
Chronic hepatitis and carrier state does not occur and complete immunity is attained after infection.
Diagnosis
- Anti-HAV IgM antibodies are diagnostic, appearing before jaundice develops, and persisting for about 3 months.
- Anti-HAV IgG antibodies denote current or past hepatitis A infection, or immunity from previous vaccination, conferring lifelong immunity.
- Serum transaminases and bilirubin levels are elevated.
Treatment
Treatment is supportive, antiviral agents have no beneficial clinical effect.
Prevention
Reduction of transmission is achieved with adequate sanitation and good personal hygiene.
Vaccination against hepatitis A is recommended for travellers to high prevalence areas, patients with chronic liver infections or severe liver disease, individuals who are at risk due to sexual behaviour or IV drug abuse, and individuals with high risk occupations e.g. individuals who work with primates, sewage workers, laboratory staff who work directly with the virus.
Immunisation should be considered for prevention of secondary cases in close contacts of confirmed cases of hepatitis A. Intramuscular normal immunoglobulin is recommended for use in addition to hepatitis A vaccine for close contacts of confirmed cases of hepatitis A who have chronic liver disease or HIV infection, or who are immunosuppressed or over 50 years of age.
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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 |
