Fever is a physiological response to disease, which facilitates and accelerates recovery. Fever is a frequent complaint at presentation, although there is no evidence that children with fever are at increased risk for serious outcomes. Parents are worried about risks such as seizures, brain damage, or death.^1,2 Caregivers are also not confident about how to manage fever in children, as there are many opinions from family members. Many drugs can be bought over the counter or prescribed to bring down fevers quickly in a sick child.² The most frequently used over-the-counter (OTC) medicines are paracetamol and ibuprofen.^1,2

However, although a common presenting complaint, fever is mostly self-limiting and is usually a result of a self-limiting viral infection. Sometimes, fevers may be caused by serious bacterial infections, such as meningitis and pneumonia, and other non-infectious illnesses. Thus, the underlying illness causing the fever needs to be determined, and it is important to be able to distinguish between a child with a high risk of a serious illness who requires specific treatment, hospitalisation, or specialist care, and those at low risk who can be managed safely at home. This article will assist primary healthcare workers and general practitioners in identifying high-risk children who present with fever, and deciding on the correct time to refer, the appropriate use of antipyretic medication, and the correct advice to be given to parents and caregivers.

There is no universal agreement as to the upper limit of the normal temperature range in humans.³ Body temperatures vary according to the location at which measurements are taken (oral, rectal, tympanic, or skin thermal scan); the type of thermometer used (contact, noncontact, or handheld thermal scanner); the time of the day; age of the patient, sex, and race.³ The World Health Organization⁴ defined fever as an axillary temperature of > 37.5°C, while other authors defined fever as a body temperature of > 38°C.^5,6,7,8 Fever without a focus is an acute febrile illness, typically less than 14 days duration, with no identifiable cause after careful history and physical examination. Chronic fever is a fever that lasts for more than 14 days, and fever of unknown origin refers to a daily or intermittent fever of at least 14 days with an uncertain cause after careful history, physical examination, and initial laboratory assessment.^5,9

Fever in children is caused by infectious and non-infectious conditions, with non-infectious disorders further categorised as inflammatory, malignant, and miscellaneous. The important infectious causes of fever that must be considered are listed in Table 1.⁹ In the South African context, given that infections are one of the quadruple burden of diseases, it is important to rule out common infections such as human immunodeficiency virus (HIV), malaria, and tuberculosis (TB).^6,9 The South African Primary Care guidelines are a good reference for the various causes of fever, including infections; however, this information is discussed under headings such as HIV, skin conditions, TB, among others. rather than a general topic of fever.¹⁰ The inflammatory disorders include mainly autoimmune conditions such as Kawasaki disease, juvenile idiopathic arthritis, inflammatory bowel diseases, and systemic lupus erythematosus. Leukaemia, lymphoma, and neuroblastoma are some of the childhood malignancies that can cause fever. The miscellaneous category of causes of fever includes drugs, toxins, post-immunisation, familial dysautonomia, and factitious disorder.

The causes of febrile illnesses differ based on whether the fever is acute, acute recurrent or periodic, or chronic.

Most acute fevers (fevers of less than 14 days’ duration) in children are caused by infection with viral respiratory or gastrointestinal infections and certain bacterial infections (otitis media, pneumonia, and urinary tract infections). Potential infectious causes of acute fever also vary with the age of the child. Neonates are considered functionally immunocompromised and at higher risk of serious infections caused by organisms acquired during the perinatal period, such as group B streptococci, Escherichia coli, and Listeria monocytogenes, which can cause bacteraemia, and herpes simplex, which can cause viraemia.⁹

Most acutely febrile children in the age group of 1 month to 2 years have self-limiting viral diseases. A minority of these children may be in the early stage of a serious infection, and the main concern in such children is whether occult bacteraemia is present. Streptococcus pneumoniae and Haemophilus influenzae type b are the most common causes of occult bacteraemia.⁹

The non-infectious causes of acute fevers include Kawasaki disease, acute rheumatic fever, diabetes insipidus, anhidrosis, heatstroke, dysautonomia, toxic ingestion of medications with anticholinergic effects, measles vaccination, and pertussis vaccination. Fever with a history of travel to disease-endemic areas should prompt the suspicion of travel-related infections (Table 2).

The causes of chronic fever can be infectious and non-infectious. Some of the common causes of chronic fever in children are listed in Table 3.

The body’s temperature is tightly regulated between 36 °C and 37.8 °C, mediated, and controlled by the central nervous system in the pre-optic area of the hypothalamus. Pathogens and tissue damage result in the release of cytokines by the reticuloendothelial system, macrophages, and endothelium. These cytokines reach the hypothalamus through the systemic circulation and trigger≈the release of prostaglandin E2 (PGE2). Prostaglandin E2 raises the thermoregulatory set point to a higher temperature, which leads to increased metabolic rate.¹¹ The increased metabolic rate produces heat, which results in fever (Figure 1).

Non-steroidal anti-inflammatory drugs (NSAID) such as ibuprofen and other antipyretics such as paracetamol lower temperature by antagonising PGE2 release. It should be noted that non-PGE2-mediated processes can cause fever as well, including increased oxygen consumption, metabolic demands, protein breakdown, and gluconeogenesis. In contrast to fever (which rarely goes above 41 °C), which is induced by cytokine activation and leads to thermoregulatory responses, hyperthermia refers to elevation of core body temperature above ‘set point’ as a result of the failure of body thermoregulation and is usually a result of excessive exogenous or endogenous heat production – heat exhaustion, heat cramps, heat stress, and heatstroke.^1,6,12

As a rule, for every 1°C core body temperature increase, the heart rate and/or pulse increases by 10 beats/min – 20 beats/min, and the respiratory rate increases by 2 breaths/min – 4 breaths/min (Liebermeister’s rule).^13,14 While tachycardia is often a normal physiologic response to increased metabolic rate caused by fever, some febrile illnesses may manifest with an unusual association of fever with relative bradycardia. This phenomenon is referred to as sphygmothermic dissociation or Faget sign, and occurs in diseases such as typhoid fever, yellow fever, dengue fever, and brucellosis.¹⁵

Fever is a symptom of an underlying illness that needs to be identified with a thorough medical history, complete physical examination, and appropriate tests or investigations if indicated.

Fever is one of the leading causes of presentations to PHC facilities in children and signifies a normal body response to an underlying inflammatory disorder. The anxiety and stress in the caregiver also need to be managed empathetically. Fever is mostly caused by infectious agents, and the focus of the healthcare practitioner is to systematically identify and manage the offending infection, being mindful of the likely causative agent in the child’s age group. While most children with uncomplicated fever can be managed on an outpatient basis in the PHC, those who present with danger signs should be stabilised and referred for hospital-based management.

In this article, we sought to provide information about the commonest causes of fever in children and to provide the primary healthcare doctor with an approach to managing this common presentation. This information will also help to allay the fears of caregivers. A limitation of this article is that the focus is on the South African context, and a general approach to fever in children is discussed; it does not go into detail on any specific condition.