12: INFECTIOUS DISEASES

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CHAPTER 12 INFECTIOUS DISEASES

Whooping cough
Meningitis
Scarlet fever
Glandular fever (infectious mononucleosis)
Hand, foot and mouth disease
Slapped cheek (fifth disease)
Chickenpox
Influenza
Pneumonia
Malaria
Conjunctivitis
Diarrhoea and vomiting
Impetigo
Cold sores
Shingles
Boils
Hepatitis
HIV/AIDS
Pyrexia of unknown origin (PUO)
Weil’s disease
Lyme disease
Measles
Mumps
Rubella

WHOOPING COUGH

Whooping cough is now rare. After a catarrhal phase, it presents as an increasingly severe and paroxysmal cough. Send a nasopharyngeal swab for diagnosis. A differential white count shows a marked lymphocytosis. The treatment of pertussis is largely symptomatic. Erythromycin given for 10 days prevents spread of the illness. It should also be given to non-immunised child contacts (for pertussis vaccine, see p. 335). Admit if symptoms are severe (can cause apnoea in the very young).

Tip

Whooping cough is a notifiable disease.

MENINGITIS

There are 2000 cases per year of bacterial meningitis in the UK. Of these, 50% are due to Neisseria meningitidis. Viral meningitis is more common.

Diagnosis

History.

Ask about:

• an acute illness of 24–48 hours’ duration
• fever
• headache
• photophobia
• drowsiness
• vomiting
• neck stiffness
• rash (N. meningitidis).

Occasionally, meningitis may develop as a complication of a pre-existing pyrexial illness, such as otitis media, in which case the deterioration will be acute, although the total duration of the illness may be several days.

Examination.

Look for:

• pyrexia
• cold peripheries
• pallor
• drowsiness
• vomiting
• pain on flexing the cervical spine
• pain on straight-leg raising
• decreased muscle tone in a baby
• irritability
• a petechial rash which does not blanch on pressure.

Tip

The early signs of meningitis are those of any pyrexial illness, e.g. pyrexia, irritability, vomiting and lethargy. Always be prepared to re-examine the patient if the condition deteriorates.

Always examine the patient for other causes of pyrexia, e.g. ears, throat, chest.

Neck pain is more often due to the cervical lymphadenopathy of an upper respiratory tract infection.

Children without meningitis are able to kiss their knees.

Management

Any patient strongly suspected of having meningitis should be seen in hospital as soon as possible, even if there is a possible alternative explanation for the patient’s condition, e.g. otitis media.

The vast majority of pyrexial patients will be found on history and examination to have no features of meningitis, and most will have an obvious alternative diagnosis. Treat as appropriate. Take the opportunity to advise the patient or the parents of the features of meningitis.

Close family and school contacts should receive rifampicin 5 mg/kg 12-hourly for 2 days.

For suspected meningitis give benzylpenicillin im/iv 600 mg under 2 years of age, 1.2 g over 2 years, immediately, before arranging urgent hospital admission. If allergic to penicillin, give cefotaxime im/iv 50 mg/kg under 12 years of age, 1 g over 12 years.

Tip

Meningitis is a notifiable disease. The hospital should notify the Environmental Health Department.

SCARLET FEVER

Scarlet fever has become less common over the last 50 years. It is caused by a β-haemolytic Streptococcus, group A.

The incubation period is 2–4 days.

Diagnosis

History.

Ask about:

• sore throat
• rash
• flushed appearance
• headache
• vomiting.

Examination.

Look for:

• tonsillitis with flecks of pus
• tender cervical lymphadenitis
• a furred tongue initially, which becomes red and smooth later
• a bright pink skin rash with tiny red spots (punctate erythema), which spares the circumoral region
• skin peeling, especially on the hands and toes, after a few days.

Investigations.

Investigations are not indicated, although β-haemolytic Streptococcus can be isolated on a throat swab, and elevated ASO titres in blood are found. Usually, by the time the results are available in general practice, the illness is all but over.

Management

Prescribe penicillin V 250–500 mg qds orally for 10 days, or erythromycin if the patient is allergic to penicillin.

Tip

Small epidemics of scarlet fever are sometimes seen.

GLANDULAR FEVER (INFECTIOUS MONONUCLEOSIS)

Glandular fever is an acute viral infection, mainly affecting teenagers, and is a common general practice problem.

The incubation period is usually 7–10 days, occasionally longer.

It can occur either sporadically or in epidemics.

Diagnosis

History.

Ask about:

• sore throat
• fever
• headaches
• tiredness
• malaise or anorexia.

These are usually of a short duration, but the condition may present after several weeks of a combination of the above, with prolonged, intermittent symptoms. Upper abdominal pain indicates hepatitis or splenic enlargement.

Examination.

Look for:

• tonsillar enlargement with exudate, which can be difficult to distinguish from bacterial or viral tonsillitis
• petechial haemorrhages on the soft palate
• posterior cervical lymphadenopathy
• hepatosplenomegaly
• maculopapular rash.

Investigations.

• An FBC and film will show a neutrophil leucocytosis of 10–20 × 109/l.
• LFTs if jaundice is present.
• A Monospot/Paul Bunnell test will be positive in most cases of glandular fever, especially if taken at least 3 weeks after the start of the illness. False-negative results are common in the first week.

Management

• Advise rest, analgesia and fluids in the acute phase.
• Avoid alcohol.
• Be aware that amoxicillin may cause a rash in glandular fever.
• Avoid contact sports while the spleen is enlarged.
• Local anaesthetic throat lozenges may be helpful.
• Metronidazole 200 mg tds may help the oral lesions.
• Prednisolone 30 mg od for 1 week may help if the symptoms are prolonged or severe.
• If the continuing symptoms are dominated by depression, consider an antidepressant.
• If lymphadenopathy, fatigue and myalgia persist beyond 3 months, consider postviral fatigue syndrome (see p. 298).

HAND, FOOT AND MOUTH DISEASE

Hand, foot and mouth disease commonly occurs in epidemics. It affects mainly young children and the incubation period is 3–7 days. It is caused by a Coxsackie virus infection.

Diagnosis

History.

Ask about mild fever and malaise, followed by red spots or vesicles in the mouth and on the lips and buttocks. Milky vesicles also appear on the hands and feet, and these may ulcerate.

Examination.

Confirms the above. More widespread vesicular lesions suggest chickenpox.

Management

• Symptomatic relief is all that is necessary, using paracetamol and fluids. Benzydamine oral spray is useful for painful oral lesions.
• The illness lasts for 7–10 days.
• Other family members are often affected.

SLAPPED CHEEK (FIFTH DISEASE)

Fifth disease is an infectious upper respiratory illness of young children, which tends to occur in small epidemics.

Diagnosis

History.

Ask about a mild illness characterised by erythema of the cheeks and accompanied by fever and irritability.

Examination

• Confirm the above.
• Exclude tonsillitis.

Management

There is no specific treatment. Paracetamol helps the fever and irritability. Associated with increased risk of miscarriage.

Tip

Red cheeks and mild fever may be due to teething in babies.

CHICKENPOX

Chickenpox is a common childhood illness in general practice, occurring usually in small epidemics.

The incubation period is 2–3 weeks.

After infection with chickenpox, the varicella-zoster virus remains dormant in dorsal root ganglia. Reactivation causes shingles (see p. 197).

Diagnosis

If the child is seen before the onset of the rash there may be a pyrexia and irritability. Otherwise the appearance of the rash is diagnostic.

Examination.

The rash starts with one or two maculopapular spots which are rapidly joined by many others. Vesicles develop from these as new spots appear. The rash is very itchy and in children scratch marks can often be seen. The whole body can be affected including the palms, soles, oral mucosa and scalp. In the final stage of the rash, after 5–10 days, the spots scab over.

Complications.

These are rare:

• chickenpox pneumonia (cough, wheeze and shortness of breath)
• encephalomyelitis (signs of meningism).

Management

• Paracetamol and calamine lotion are often all that are needed. Overheating tends to make the spots itch more. If impetigo develops in any of the spots, use fusidic acid ointment tds or oral flucloxacillin.
• In adults consider antiviral agent, e.g. aciclovir 800 mg five times daily for 7 days.

Is the patient immunocompromised or pregnant? If so, varicella zoster immunoglobulin may be needed (see p. 343).

INFLUENZA

Influenza commonly occurs as a winter and spring epidemic.

The incubation period is 24–48 hours.

Diagnosis

History.

Ask about:

• pyrexia
• headache
• coryza
• sore throat
• mild photophobia
• malaise and myalgia.

Examination.

Look for:

• pyrexia
• blocked nose
• mild conjunctivitis
• red throat and cervical lymphadenopathy.

Exclude a chest infection, tonsillitis, otitis and meningitis.

Tip

Postinfluenza bronchopneumonia is more common in the elderly and infirm and is suspected at the onset of a productive cough, shortness of breath, pleuritic chest pain or prolongation of the fever. Treat with oral flucloxacillin 500 mg qds for 7 days.

Management

• Rest.
• Analgesic/antipyretic, e.g. aspirin or paracetamol.
• Good fluid intake.
• Reassure patient that they should make a full recovery in 5–6 days.
• Antivirals, e.g. oseltamivir or zanamivir, are recommended when influenza is circulating in the community and if an at-risk patient can start treatment within 48 hours of the onset of symptoms. At-risk patients are those eligible for immunisation against influenza.
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