Category Archives: Infectious disease

Pyrexia of Unknown Origin

A technical term, not just a fever without obvious source! Essentially presence of confirmed fever for 8 days or more in a child in whom a careful thorough history and physical examination, and preliminary laboratory data fail to reveal a probable cause.

Long list of possible causes, long lists of possible tests – do thorough history and repeated examinations, then follow the clues!

In kids, infection is the commonest cause. But can be connective tissue disorder, or malignancy.

Beware factitious fever – admission sensible.

If possible, stop all drugs. Antipyretics may obscure the pattern of fever, and can occasionally be its cause (drug fever is one cause).

Unless the child is critically ill, try not to give antibiotics. If the diagnosis remains obscure, go back and take the history again, examine the child (fully) again, send the specimens again!

Special points in history/examination

  • Travel – malaria can present 6-12 months later. Typhoid.
  • Ethnicity – tuberculosis
  • Outdoor activities – rats/ticks as vectors of infectious diseases
  • Animal contact – cows/sheep (brucellosis), cats (cat scratch)
  • Mouth ulcers (IBD, Behcets, PFAPA)
  • Periodicity – see Periodic fever
  • Sinus tenderness, nasal congestion (sinusitis)
  • Bone/spine tenderness – discitis, vertebral osteomyelitis


  • 3 sets of blood cultures, different sites, different times (at least a few hours apart), off antibiotics – standard for endocarditis
  • ASOT
  • EBV, CMV
  • LDH, CK
  • ANA/RF
  • Urine/stool culture
  • Swab everything!
[Rosie Hague, Current peds 2001]


=periodic fever, aphthous stomatitis, pharyngitis, adenitis.

Fever every 4-6 weeks (periodic). Neutrophil count normal, cf cyclical neutropenia.

Besides mouth ulcers, sore throat and cervical lymphadenopathy, headache, musty smell (!), abdo pain.

Affected children continue to grow normally, are well between attacks, and do not suffer long-term sequelae.

Treatment with steroids or with cimetidine has been effective, and some children have had no further attacks following tonsillectomy (which suggests some relationship with strep infection but not clear).

Periodic fever

Infectious causes
Mycobacteria (TB and non-tuberculous disease)
Streptobacillus moniliformis (rat bite fever)
Hepatitis B
Rickettsea (typhus)
Entamoeba histolytica
Cyclical neutropoenia
Hyper IgD (HIDS)
Familial Mediterranean fever
Familial Hibernian fever/TRAPS
Cryopyrin disorder

Periodic fevers are defined as uniform periods of fever that recur regularly in individuals who are healthy between attacks. Parents may organize life eg holidays around expected attacks and don’t have any concerns otherwise cf child with recurrent respiratory and gastrointestinal infections after starting nursery who “always has something”.

Recurrent bacterial infections esp recurrent/chronic pneumonia or otitis media may indicate a humoral immune defectSimilarly, recurrent documented viral or fungal infections may indicate a cell mediated immune defect.

Tick borne encephalitis

Arbovirus, spread by ticks, big problem in forested regions of Europe and vaccine available.

In Scotland, “Louping ill” is tick born encephalitis affecting sheep – v rarely humans too.

Since 2019, 3 cases of TBE in England (virus had been found in ticks in Southern England before), and recently 1 in Scotland. Patient had a dozen or so ticks that were only removed after a day.

Lyme disease is the other important tick borne infection.

Orbital cellulitis

Potentially serious infection of the eye.

Chandler classification describes the potential sequence of events:

  • Preseptal (periorbital) cellulitis, in other words, anterior to the eye. Usually caused by skin organisms entering via superficial trauma
  • Orbital cellulitis – surrounding the eye
  • Subperiosteal orbital abscess – penetration into bone of orbit
  • Orbital abscess
  • Cavernous sinus thrombosis

In older children, more likely to start with sinusitis, then eroding through into orbit. Differentiating between these types is difficult without imaging.

Different organisms cf skin commensals of preseptal cellulitis eg Haemophilus, streptococci including pneumococcus, anaerobes.

Often no organism is obtained, which adds to the difficulty of giving evidence based guidance. Multiple bugs not uncommon. Hence a variety of different guidelines, generally of poor quality.

In a large US review of 220 children and young adults, 98% were investigated by CT. High rate of steroid use – previous studies have suggested better outcomes, but no obvious benefit in terms of treatment success here. Various antibiotic regimens, various durations. More treatment failures if treated for more than 3 weeks but these will be the most severe/complex cases.


Jointly managed by ophthalmology, ENT and paediatrics. Ophthalmology are best at performing eye movement assessment, but it is ENT who tend to do any surgery (usually endoscopic sinus surgery).

Red flags:

  • Severe proptosis,
  • worsening visual acuity,
  • elevated intraocular pressure,
  • colour indiscrimination,
  • intracranial involvement,
  • inability to perform a reliable serial ophthalmologic examination,
  • poor response to a trial of intravenous antibiotics for 24 to 48 hours

These are indications for surgery.

The size of any subperiosteal abscess on CT is a new prognostic factor: diameter >10mm and volumes ≥500mm3 (although volume measurements not routinely reported) are thought typically to require immediate surgical intervention, with the remainder going to surgery only in the event of clinical deterioration, lack of clinical improvement after 48 hours of antibiotics, or worsening abscess on imaging.

Treatment duration – most people would agree to IV treatment until clear improvement, followed by oral antibiotics for a total of 14 days.


Doesn’t seem to be associated with severity of initial illness.

Long COVID is less common if you are vaccinated already. In a community based study of adults aged 18 to 69 years infected with SARS-CoV-2 before vaccination against covid-19, the odds of experiencing long covid symptoms decreased by an average of 13% after a first covid-19 vaccine dose, with a further 9% decrease in the odds of long covid after a second dose. [

If you already have long COVID, further COVID immunisations seem to be beneficial, rather than harmful:

  • In a non-controlled study of 900 social media users with long COVID, more than half experienced an improvement in symptoms after vaccination compared with 7% who reported a deterioration.19
  • A study of 44 vaccinated patients and 22 unvaccinated controls previously admitted to hospital with covid-19 in the UK, which inevitably had limited power to detect clinically relevant effects, found no evidence for vaccination being associated with worsening of long covid symptoms or quality of life.20
  • A French study of 455 self-selected participants found reduced long COVID symptom burden and double the rate of remission at 120 days in vaccinated participants compared with unvaccinated controls.

All about symptoms, excluding treatable conditions, then self management. For adults:


=enterobius. Common in young children, probably due to hygiene issues. Also called pinworms. Small (1-2cm), like white threads. Can be intensely itchy, usually in night when worms emerge to lay eggs.

Mebendazole effective at killing live worms in gut, not effective if eggs in vagina. Licensed from age 2 but can be used off license below that. Does not kill eggs however, and main issue is reinfection so consider treating whole family, with repeat doses after 2 weeks when any eggs will have hatched, and follow NHS Inform advice on hygiene.

Sometimes you just have to keep repeating treatment over months/years! Mebendazole is harmless, although symptoms may be caused by clearance of large worm burdens.


Typically P. aeruginosa. A biofilm producing gram negative bacterium important in multiresistant infections, particularly in the immunocompromised and in cystic fibrosis.

Pretty ubiquitous in the environment, especially in lakes and rivers. Often found in vases of cut flowers, and in spa/whirlpool baths, where it is associated with folliculitis.

The ability to make biofilms makes infection difficult to treat, as the biofilm prevents penetration by antibiotics. The biofilm allows the bugs to survive in low nutrient environments.

Antibiotic resistance is a major issue, with specific anti-pseudomonal antibiotics often required viz tobramycin, ceftazidine.

Ingesting pseudomonas doesn’t pose much of a hazard, unless you are on antibiotics already and have a disturbed intestinal flora. Aerosolizing pseudomonas on the other hand can be lethal to mice.

[DOI: 10.1007/978-1-4419-0032-6_3]